NZ625401B2 - Method for improved transformation using agrobacterium - Google Patents

Abstract

Disclosed is a method for plant cell transformation comprising exposing immature embryo plant cells to Agrobacterium cells in a liquid medium containing a non-ionic trisiloxane surfactant, the surfactant having a concentration of 0.001 weight percentage to 0.08 weight percentage in the liquid medium, and wherein the non-ionic trisiloxane surfactant is not a trisiloxane alkoxylate. , and wherein the non-ionic trisiloxane surfactant is not a trisiloxane alkoxylate.

Description

METHOD FOR IMPROVED TRANSFORMATION USING AGROBACTERIUM CROSS REFERENCE TO D APPLICATIONS This application claims the benefit of US. Provisional Patent Application Serial No. 61/576,138 filed December 15, 2011.

BACKGROUND Plant transformation generally encompasses the methodologies required and utilized for the introduction of a plant—expressible foreign gene into plant cells, such that fertile progeny plants may be obtained which stably maintain and express the foreign gene. Numerous members of the monocotyledonous and ledonous classifications have been transformed. Transgenic agronomic crops, as well as fruits and vegetables, are of commercial interest. Such crops e but are not limited to maize, rice, soybeans, canola, er, alfalfa, m, wheat, cotton, peanuts, tomatoes, potatoes, and the like.

Several techniques are known for introducing foreign genetic material into plant cells, and for obtaining plants that stably maintain and express the introduced gene. Such techniques include acceleration of genetic material coated onto microparticles directly into cells (cg, US.

Patent No. 050 and US. Patent No. 5,141,131). Other transformation technology includes WHISKERSTM technology (see, e.g., US. Patent No. 5,302,523 and US. Patent No. 5,464,765). oporation technology has also been used to transform plants. See, e.g, WO 87/06614, US. Patent No. 5,472,869, US. Patent No. 5,384,253, WO 92/09696, and WO 93/21335.

Additionally, fusion of plant lasts with liposomes containing the DNA to be delivered, direct ion of the DNA, as well as other possible methods, may be employed.

Once the inserted DNA has been integrated into the plant genome, it is usually relatively stable throughout uent generations. The transformed cells grow inside the plants in the usual manner. They can form germ cells and transmit the transformed trait(s) to progeny plants. Such plants can be grown in the normal manner and may be crossed with plants that have the same transformed hereditary factors or other hereditary factors. The ing hybrid individuals have the corresponding ypic properties, for example, the ability to control the feeding of plant pest insects. 1001685931 A number of alternative techniques can also be used for inserting DNA into a host plant cell. Those techniques include, but are not limited to, transformation with T—DNA delivered by Agrobacterium tumefaciens or Agrobacz‘erium rhizogenes as the transformation agent. Plants may be ormed using Agrobacterium technology, as described, for example, in US. Patent No. 5,177,010, US. Patent No. 5,104,310, European Patent Application No. 013 1624B 1, European Patent Application No. 120516, European Patent Application No. 159418B1, European Patent Application No. , US. Patent No. 5,149,645, US. Patent No. ,469,976, US. Patent No. 5,464,763, U.S. Patent No. 4,940,838, US. Patent No. 4,693,976, European Patent Application No. , European Patent Application No. , European Patent Application No. , European Patent Application No. 604662, an Patent Application No. 627752, European Patent Application No. 0267159, European Patent Application No. 0292435, US. Patent No. 019, US. Patent No. 5,463,174, US. Patent No. 785, US. Patent No. 5,004,863, and US. Patent No. 5,159,135. The use ofT-DNA— ning vectors for the transformation of plant cells has been intensively researched and sufficiently described in European Patent Application 120516; An et al., (1985, EMBO J. 4:277— 284); Fraley et al., (1986, Crit. Rev. Plant Sci. 4: 1~46), and Lee and Gelvin (2008, Plant Physiol. 146:325—332), and is well established in the field.

A critical first step in the transformation of plant cells by Agrobacterium spp. is close contact, binding, or nce ofthe bacterial cells to the cells ofthe host plant to be transformed. After cell—cell binding, the biology of T—DNA transfer from Agrobacterium to plant cells is known. See, e.g., Gelvin, 2003, Microbiol. Molec. Biol. Rev. 67:16—37; and Gelvin, 2009, Plant Physiol. 150: 1665—1676. At minimum, at least a T—DNA right border repeat, but often both the right border repeat and the left border repeat of the Ti or Ri plasmid will be joined as the flanking region of the genes desired to be inserted into the plant cell. The left and right T—DNA border repeats are crucial cis—acting sequences required for T—DNA transfer.

Various trans—acting components are encoded within the total Agrobacterium genome. Primary amongst these are the ns encoded by the vir genes, which are normally found as a series of operons on the Ti or Ri plasmids. s Ti and Ri plasmids differ somewhat in the complement of vir genes, with, for example, virF not always being present. Proteins encoded by vir genes perform many different functions, ing recognition and signaling of plant cell/bacteria interaction, induction of vir gene ription, formation of a Type IV secretion 1001685931 channel, recognition ofT—DNA border repeats, formation of T-strands, transfer of T-strands to the plant cell, import of the T—strands into the plant cell s, and integration of T-strands into the plant nuclear chromosome, to name but a few. See, e.g, Tzfira and Citovsky, 2006, Curr.

Opin. Biotechnol. -154.

IfAgrobacterium strains are used for transformation, the DNA to be inserted into the plant cell can be cloned into special plasmids, for example, either into an intermediate (shuttle) vector or into a binary vector. Intermediate vectors are not capable of independent replication in cterium cells, but can be manipulated and replicated in common Escherichia coli molecular cloning strains. It is common that such intermediate s comprise sequences, framed by the right and left T—DNA border repeat regions, that may include a selectable marker gene functional for the selection of transformed plant cells, a cloning linker, cloning polylinker, or other sequence which can function as an introduction site for genes destined for plant cell transformation. Cloning and lation of genes desired to be transferred to plants can thus be easily performed by standard methodologies in E. coli, using the shuttle vector as a cloning vector. The finally manipulated shuttle vector can subsequently be introduced into Agrobacterium plant transformation s for further work. The intermediate vector can be transferred into Agrobacterium by means of a helper plasmid (via bacterial conjugation), by oporation, by chemically mediated direct DNA transformation, or by other known methodologies. Shuttle s can be integrated into the Ti or Ri plasmid or derivatives thereof by homologous recombination owing to sequences that are homologous between the Ti or Ri plasmid, or derivatives thereof, and the intermediate plasmid. This homologous recombination (i.e. plasmid integration) event thereby provides a means of stably maintaining the altered shuttle vector in Agrobacterium, with an origin of replication and other plasmid maintenance functions provided by the Ti or Ri d portion of the co~integrant d. The Ti or Ri plasmid also comprises the vir regions comprising vir genes necessary for the transfer of the T—DNA. It is common that the plasmid carrying the vir region is a mutated Ti or Ri plasmid r plasmid) from which the T-DNA region, including the right and left T—DNA border repeats, have been deleted. Such pTi-derived plasmids, having onal vir genes and g all or substantially all of the T—region and associated ts are descriptively referred to herein as helper plasmids. 1001685931 The superbinary system is a specialized example of the shuttle vector/homologous recombination system (reviewed by Komari er al., 2006, I_n: Methods in Molecular Biology (K.

Wang, ed.) No. 343: Agmbacterium ols, pp.15-4l; and Komori et al., 2007, Plant Physiol. 145:1155-1160). Strain 4(pSB 1) harbors two independently-replicating plasmids, pAL4404 and pSB l. pAL4404 is a smid-derived helper plasmid which contains an intact set of vir genes (from Ti plasmid pTiACHS), but which has no T—DNA region (and thus no T— DNA left and right border repeat sequences). Plasmid pSBl supplies an additional partial set of vir genes derived from pTiB0542; this partial Vir gene set includes the virB operon and the virC , as well as genes virG and virD] . One example of a shuttle vector used in the superbinary system is pSBl l, which ns a cloning polylinker that serves as an introduction site for genes destined for plant cell transformation, flanked by Right and Left T—DNA border repeat regions. Shuttle vector pSBll is not capable of independent replication in Agrobacterium, but is stably maintained as a co—integrant plasmid when integrated into pSBl by means of homologous recombination between common sequences present on pSBl and p88] 1.

Thus, the fully modified T—DNA region introduced into LBA4404(pSB 1) on a modified pSB l 1 vector is productively acted upon and erred into plant cells by Vir ns d from two different Agrobacterium Ti plasmid sources (pTiACHS and pTiB0542). The Agrobacterium tumefaciens host strain ed with the superbinary system is LBA4404(pSBl). The superbinary system has proven to be particularly useful in transformation of monocot plant species. See Hiei et al., (1994) Plant J. 62271—282; and lshida et al., (1996) Nat. Biotechnol. —750.

In addition to the vir genes ed by Agrobacterium Ti ds, other, chromosomally-borne virulence controlling genes (termed chv genes) are known to control certain aspects of the interactions ofAgrobacterium cells and plant cells, and thus affect the overall plant transformation frequency (Pan et (11., 1995, Molec. Microbiol. 17:259—269). Several of the chromosomally-borne genes required for Virulence and attachment are grouped together in a chromosomal locus spanning 29 kilobases (Matthysse et al., 2000, Biochim. Biophys. Acta 1490:208-212).

In on to numerous technologies for transforming plants, the type of tissue which is contacted with the foreign genes may vary as well. Such tissue may include, but is not limited to, embryogenic tissue, callus tissue types I and II, hypocotyl, and meristem. Almost all plant 1001685931 tissues may be ormed during dedifferentiation using appropriate techniques within the skill of an artisan. One skilled in the field of plant transformation will understand that multiple methodologies are available for the production of transformed plants, and that they may be modified and specialized to accommodate ical differences between various host plant species. Plant ts (for example, pieces of leaf, ts of stalk, meristems, roots, but also protoplasts or sion-cultivated cells) can ageously be cultivated with Agrobacterium tumefaciens or Agmbacz‘erium rhizogenes for the transfer of the DNA into the plant cell.

Callus cultures Plant tissue cultures may advantageously be cultivated with Agrobacterium tumefaciens or Agrobacterz'um rhizogenes for the transfer of the DNA into the plant cell, and are generally initiated from sterile pieces of a whole plant that may consist of pieces of organs, such as leaves or roots, or maybe specific cell types, such as pollen or endosperm. Many features of the explant are known to affect the efficiency of culture initiation.

It is thought that any plant tissue can be used as an explant, if the correct conditions are found. lly, younger, more rapidly growing tissue (or tissue at an early stage of development) is most ive. Explants cultured on the appropriate medium can give rise to an unorganized, g, and dividing mass of cells (callus). In culture, callus can be maintained more or less indefinitely, provided that it is subcultured on to fresh medium periodically. During callus formation, there is some degree of de-differentiation, both in morphology (a callus is usually composed of unspecialized parenchyma cells) and metabolism.

Callus cultures are extremely important in plant biotechnology. Manipulation of the plant hormone ratios in the culture medium can lead to the development of shoots, roots, or somatic embryos from which whole plants can uently be produced (regeneration). Callus cultures can also be used to initiate cell suspensions, which are used in a variety of ways in plant transformation studies.

Cell suspension cultures Callus cultures, y speaking, fall into one oftwo categories: compact or friable. In compact callus, the cells are y aggregated, whereas in friable callus, the cells are only loosely associated with each other and the callus becomes soft and breaks apart easily. Friable callus provides the um to form cell-suspension cultures. ts from some plant species or particular cell types tend not to form friable callus, making it difficult to initiate cell suspension. The friability of the callus can sometimes be improved by manipulating the medium components, by repeated subculturing, or by ing it on semi-solid 1001685931 medium m with a low tration of gelling agent). When friable callus is placed into a liquid medium and then agitated, single cells and/or small clumps of cells are released into the medium. Under the correct conditions, these released cells ue to grow and divide, eventually ing a cell-suspension culture. Cell suspensions can be ined relatively simply as batch cultures in conical flasks and are propagated by repeated subculturing into fresh medium. After subculture, the cells divide and the biomass of the culture increases in characteristic fashion. Cell suspension cultures may advantageously be cultivated with Agrobacterium tumefaciens or Agrobacterium rhizogenes for the transfer of the DNA into the plant cell.

Shoot tip and meristem culture The tips of shoots (which contain the shoot apical meristem) can be cultured in vitro, producing clumps of shoots from either axillary or adventitious buds and may advantageously be cultivated with Agrobaclerium lumefociens Agrobacterium rhizogenes for the transfer of the DNA into the plant cell. Shoot meristem cultures are used for cereal regeneration (seedlings can be used as donor material).

Embryo culture Embryos can be used as explants to generate callus cultures or somatic s. Both immature and mature embryos can be used as explants. Immature, embryo—derived genic callus is a tissue used in monocotyledon plant regeneration and may advantageously be cultivated with Agrobacterium lumefaciens for the transfer of the DNA into the plant cell. Immature embryos are an intact tissue that is e of cell division to give rise to callus cells that can differentiate to produce tissues and organs of a whole plant.

Immature embryos can be obtained from the fertilized ears of a mature maize plant, for e, from plants pollinated using the methods fer et al. (1982, Growing maize/or purposes. In: Maize for Biological Research. W. F. an, Ed. UNIVERSITY PRESS, University ofNorth , Grand Forks, ND). Exemplary methods for isolating immature embryos from maize are described by Green and Phillips (Crop Sci. 15:417-421 (1976)).

Immature embryos are preferably isolated from the developing ear using aseptic methods and held in sterile medium until use. The use ofAgrobacterium in transformation of immature embryos is disclosed by Sidorov & Duncan, (2009, Methods in Molecular Biology: Transgenic Maize, vol.526 Chapter 4, M. Paul Scott (Ed.)) and in US. Patent No. 840.

Microspore culture Haploid tissue can be cultured in vitro by using pollen or anthers as an explant and may advantageously be cultivated with Agrobacterium tumefaciens for the 1001685931 transfer of the DNA into the plant cell. Both callus and embryos can be produced from pollen.

Two approaches can be taken to e cultures in vitro from haploid tissue. In the first, anthers (somatic tissue that surrounds and contains the pollen) are cultured on solid medium.

Pollen-derived embryos are subsequently produced via dehiscence of the mature anthers. The dehiscence of the anther s both on its isolation at the t stage and on the correct culture conditions. In some s, the reliance on natural dehiscence can be circumvented by cutting the wall of the . In the second method, anthers are cultured in liquid medium, and pollen released from the anthers can be d to form embryos. Immature pollen can also be extracted from developing anthers and cultured directly.

Many of the cereals (rice, wheat, barley, and maize) require medium supplemented with plant growth tors for pollen or anther culture. Regeneration from microspore explants can be obtained by direct embryogenesis, or via a callus stage and subsequent embryogenesis.

Haploid tissue cultures can also be initiated from the female gametophyte (the ovule).

In some cases, this is a more efficient method than using pollen or anthers.

Plants ed from haploid cultures may not be haploid. This can be a consequence of chromosome doubling during the culture period. Chromosome doubling (which may be induced by treatment with chemicals such as colchicine) may be an advantage, as in many cases haploid plants are not the desired outcome of regeneration from haploid tissues. Such plants are often referred to as di—haploids, because they contain two copies of the same haploid genome.

Following transformation of any of the aforementioned plant materials by cultivation with Agrobaclerium tumefaciens for the transfer of the DNA into the plant cell, whole plants may then be regenerated from the infected plant material following ent in suitable growth conditions and culture medium, which may contain antibiotics or herbicides for selection of the transformed plant cells. The plants so obtained can then be tested for the presence of the inserted DNA.

Cell transformation (including plant cell transformation) may involve the construction of an expression vector which will on in a ular cell. Such a vector may comprise DNA that includes a gene under control of, or ively linked to, a regulatory element (for example, a promoter). The expression vector may n one or more such operably-linked gene/regulatory t combinations. The (s) may be in the form of a plasmid and can be used alone or in combination with other plasmids to provide transformed cells using 1001685931 transformation methods as described herein to incorporate transgene(s) into the genetic material of a plant cell.

Plant cell expression vectors may include at least one genetic marker, operably linked to a regulatory element (a promoter, for example) that allows transformed cells ning the marker to be either recovered by negative selection (22a, inhibiting growth of cells that do not contain the able marker gene) or by ve selection (226., screening for the t d by the genetic marker). Many selectable marker genes suitable for plant transformation are well known in the transformation arts and include, for example, genes that code for enzymes that metabolically detoxify a selective chemical agent which may be an antibiotic or an herbicide, or genes that encode an altered target which may be insensitive to the inhibitor. A few positive selection methods are also known in the art. The individually ed selectable marker gene may accordingly permit the selection oftransformed cells while the growth of cells that do not contain the inserted DNA can be suppressed by the selective compound. The preference for a particular selectable marker gene is at the discretion of the artisan, but any of the following able markers may be used, as well as any other gene not listed herein which could function as a selectable . Examples of selectable markers include, but are not d, to ance or tolerance to Kanamycin, G418, Hygromycin, Bleomycin, Methotrexate, Phosphinothricin (Bialaphos), Glyphosate, Imidazolinones, Sulfonylureas and Triazolopyrimidine herbicides, such as Chlorosulfuron, Bromoxynil, and DALAPON.

In addition to a selectable marker, it may be desirable to use a reporter gene. In some instances a reporter gene may be used without a selectable marker. Reporter genes are genes which typically do not provide a growth age to the ent organism or tissue. The reporter gene typically encodes for a protein which provides for some phenotypic change or enzymatic property. le reporter genes include, but are not limited to, those that encode beta—glucuronidase (GUS), firefly luciferase, or scent proteins such as green fluorescent protein (GFP) or yellow fluorescent protein (YFP, essentially as disclosed in US. Patent No. 7,951,923).

Regardless of transformation technique utilized, the foreign gene can be incorporated into a gene transfer vector adapted to express the foreign gene in the plant cell by including in the vector a plant promoter. In addition to plant promoters, promoters from a variety of sources can be used efficiently in plant cells to express foreign genes. For example, promoters of 1001685931 bacterial origin, such as the octopine synthase promoter, the nopaline synthase promoter, the mannopine synthase promoter; promoters of Viral origin, such as the 358 and 198 promoters of cauliflower mosaic Virus (CaMV), a promoter from sugarcane bacilliforrn Virus, and the like may be used. Plant-derived promoters include, but are not limited to ribulose-l,6-bisphosphate (RUBP) carboxylase small t (ssu), beta-conglycinin promoter, phaseolin promoter, ADH (alcohol dehydrogenase) er, hock promoters, ADF (actin depolymerization factor) promoter, and tissue specific promoters. Promoters may also contain certain enhancer sequence elements that may improve the transcription ncy. l enhancers include, but are not limited to, alcohol dehydrogenase l (ADHl) intron 1 and ADHl-intron 6. Constitutive promoters may be used. Constitutive promoters direct continuous gene expression in nearly all cells types and at nearly all times (Lag. actin, ubiquitin, CaMV 358). Tissue specific promoters are responsible for gene expression in specific cell or tissue types, such as the leaves or seeds Examples of other promoters that may be used include those that are active during a certain stage of the plant's development, as well as active in c plant tissues and organs Examples of such promoters include, but are not limited to, promoters that are root specific, pollen—specific, embryo specific, corn silk c, cotton fiber specific, seed erm specific, and phloem specific.

Under certain circumstances, it may be desirable to use an inducible promoter. An inducible promoter is responsible for expression of genes in se to a c signal, such as: physical stimulus (ag. heat shock genes); light (e. g. Ribulose—bis—phosphate 1,5 carboxylase); hormone (e. g. glucocorticoid); antibiotic (e.g. Tetracycline); metabolites; and stress (eg. drought). Other desirable transcription and translation elements that function in plants also may be used, such as, for e, 5' untranslated leader sequences, and 3' RNA transcription ation and poly—adenylate addition signal sequences. Any suitable plant— specific gene transfer vector known to the art may be used. enic crops containing insect resistance (IR) traits are prevalent in corn and cotton plants hout North America, and usage of these traits is expanding globally.

Commercial transgenic crops combining IR and herbicide tolerance (HT) traits have been developed by multiple seed companies. These include combinations of IR traits conferred by Bacillus thuringiensis (B.t.) insecticidal proteins and HT traits such as tolerance to Acetolactate Synthase (ALS) inhibitors such as Sulfonylureas, olinones, Triazolopyrimidine, 1001685931 Sulfonanilides, and the like, Glutamine Synthetase (GS) inhibitors such as Bialaphos, Glufosinate, and the like, 4-HydroxyPhenyleruvate Dioxygenase (HPPD) inhibitors such as Mesotrione, Isoxaflutole, and the like, S—EnoleruvylShikimatePhosphate Synthase (EPSPS) inhibitors such as Glyphosate and the like, and Acetyl—Coenzyme A ylase (ACCase) inhibitors such as Haloxyfop, Quizalofop, op, and the like. Other examples are known in which transgenically provided proteins provide plant tolerance to ide chemical classes such as phenoxy acids herbicides and loxyacetates auxin herbicides (see A2), or phenoxy acids ides and aryloxyphenoxypropionates herbicides (see WO 2005/l07437Al). The ability to control multiple pest problems through 1R traits is a valuable cial product concept, and the convenience of this product concept is enhanced if insect control traits and weed control traits are combined in the same plant. Further, improved value may be obtained via single plant combinations of [R traits conferred by a B.t. insecticidal protein with one or more additional HT traits such as those mentioned above, plus one or more additional input traits (e. g. other insect resistance conferred by B.t.—derived or other insecticidal proteins, insect ance conferred by mechanisms such as RNAi and the like, disease resistance, stress tolerance, improved nitrogen utilization, and the like), or output traits (e. g. high oils content, healthy oil ccmposition, nutritional improvement, and the like). Such combinations may be obtained either through conventional breeding (e.g. breeding stack) or jointly as a novel transformation event involving the simultaneous introduction of le genes (eg lar stack). Benefits include the y to manage insect pests and improved weed control in a crop plant that provides secondary benefits to the producer and/or the consumer. Thus, the methods of this disclosure can be used to provide transformed plants with combinations of traits that comprise a te agronomic package of improved crop quality with the ability to flexibly and cost effectively control any number of mic issues.

SUMMARY Methods for plant cell transformation are described. These s include exposing the plant cells to Agrobacterium cells in a liquid medium containing a surfactant. The Agrobacterium cells can be scraped from a solid medium or grown in a liquid growth medium prior to being suspended in the liquid medium containing the surfactant. The concentration of surfactant can be in the range of 0.001 weight percent to 0.08 weight t. The surfactant can 1001685931 be a non-ionic trisiloxane surfactant and more than one surfactant can be used. The plant cells can be maize cells. The plant cells can be exposed to continuous light after exposure to the Agrobacz‘erium cells.

DESCRIPTION OF DRAWINGS Figure l is a bar graph showing the enhancement of maize immature embryo transformation when the surfactant THRU® S 233 is added to the Infection Medium used to create a suspension ofAgmbacterium cells (harboring plasmid pEPSlOS3) prior to co— cultivation.

Figure 2 is a bar graph showing the enhancement of maize re embryo transformation when the surfactant BREAK~THRU® S 233 is added to the Infection Medium used to create a suspension ofAgrobacz‘erium cells prior to co-cultivation. The Plasmids used for each ment shown in Figure 2 include: Experiment 1 = pEPS1053; GOI = IPT, selectable marker = aad]. Experiment 2 = pEPS 1038; GOI=GF14, able marker = aadl. Experiment 3 and Experiment 4 = pEPSlOZ7; no GOI, selectable marker = aad].

DETAILED PTION Methods to increase transformation ncy in plants when using cterium are described. The methods include exposing plant cells to Agrobacterium cells in a liquid medium containing a surfactant. Some methods include exposing the plant cells to continuous light after exposure to the Agrobaclerium cells. es ofplants useful with these methods include maize plants and immature maize embryos. s ofAgrobacterz‘um differ from one another in their ability to transform plant cells of various species. Regardless of the particular combination ofAgrobacterium strain/host plant considered, Agrobacterium acts through attachment to the host cell during transformation.

See McCullen and Binns, 2006, Ann. Rev. Cell. Dev. Biol. 22:101w127; and Citovsky et al., 2007, Cell. Microbiol. 929—20. For this reason, methods that enhance binding ofAgmbacterium cells to plant cells, such as those disclosed herein using surfactants, may e increases in transformation efficiency. Enhancing the binding ofAgrobacterium cells to plant cells is different for ent species and tissue types as different plant species, and further, different tissues of a plant of a single species, can differ in chemical and biochemical composition of their 1001685931 cell walls. Further, such ences may also vary during different developmental stages of a single plant tissue.

Additionally different genera and species of bacteria, and indeed, different strains of a bacterial species, often differ in chemical and biochemical composition of their cell walls, and these differences can change during the bacterial growth cycle. Increases in plant ormation efficiencies by the methods disclosed herein thus may result from the ability of surfactants to se hydrophobic repulsive interactions between crerz’um cell walls and plant cell walls, and thus allow intimate ell interactions to occur.

One may therefore utilize the chemical differences between different tant agents to promote cell—cell ctions between cells ofdifferent Agrobacterium strains (and different growth phases of such cells) and cells and tissues of different host plants during various phases of e of the plant tissues so that enhanced transformation efficiencies may be observed.

Surfactants belong to several chemical classes, and one skilled in the field ofplant transformation will understand that different chemical classes of surfactants may be used to enhance plant transformation efficiency with different plant hosts. Examples of surfactants from these al classes useful with the s disclosed herein include adjuvants, non-ionic surfactants, anionic tants, oil based surfactants, amphoteric surfactants, and polymeric surfactants. An example of a preferred surfactant useful with the methods described herein is a non—ionic trisiloxane surfactant such as BREAK—THRU® S233 from Evonik Industries (Essen, Germany). Examples of further preferred surfactants useful with the methods described herein include trisiloxane alkoxylates, ethoxylated soybean oils, l ethoxylate C—13s, C12-C14— alkyldimethyl betaines, and di—sec—butylphenol ethylene oxide—propylene oxide block co— polymers. Table 1 presents an non-limiting list of surfactants of various chemical type that be used to practice the methods described herein.

Table l. Surfactants grouings, cial names and chemicalalction/class.

EVONIK BREAK-THRU® Polyether—modified INDUSTRIES AG Adjuvant S 240 polysiloxane (Essen, Germany) BREAK—THRU® Organo-modified EVONIK S 243 polysiloxane INDUSTRIES AG 1001685931 anew SILWET® 618 Trisiloxane alkoxylate ELLIOTT Blend of organosilicone & HI~WETT® ' ~ CHEMICALS LTD. other organic fluids.

(Aukland, NZ) DOW CORNING SYLGARD® 309 Non—ionic silicone surfactant (Midland, MI) HENKEL AGRIMUL® PG 2069 Alkylpolyglucoside CORPORATION (Berkeley, CA) MONSON Alcohol ethoxylate C~l3 TRYCOL® 5941 IES, INC (9 mole EO*) (Leominster, MA) Alcohol ethoxylate (3-13 STEPAN COMPANY Non-ionic MAKON® TD—6 (6 mole E0) (Northtield, IL) tant AICOhOl Ethoxylate C _ 13 MAKON® TD~12 STEPAN COMPANY (12 mole EO) l ethoxylate C~13 TRYCOL® 5993A MONSON (3 mole EO) COMPANIES, INC AGRILIANCE LLC Non—ionic surfactant and PREFERENCE® . . (Inver Grove Heights, anti—foamlng agent . BASF PLURONIC® P105 gi‘ififggli‘gp:51);1:36 CORPORATION p y nnati, OH) A ' ' HUNTSMAN 3:31 fionate yS d' 1m alk I benzene NANSA® HS 90/s CORPORATION S gig;“ a p (The Woodlands, TX) SLS (no trade name) SIGMA—ALDRICH Sodlum lauryl sulfate.

(St. Louis, MO) EMERY®/EMGARD® HENKEL Methyloleate/surfactants ATION Ethoxylated soybean oil AGNIQUE® SBO—IO BASF Oil-based (10 mole POE**) CORPORATION di-sec-butylphenol ne DOW UPTAKE® oxide—propylene oxide block AGROSCIENCES co-polymer (Indianapolis, IN) LOVELAND LI-700® soy-oil derived, nic PRODUCTS INC. penetrating surfactant (Greele , CO) 1001685931 X® (C-12) Amine oxide STEPAN COMPANY AKZONOBEL 100% Alkoxylated fatty ADSEE® AB 650 ' ’ SURFACE Amphoteric 2:21;: + wetting agent + CHEMISTRY LLC surfactant (Chicago, IL) BREAK-THRU® G Fatty acid amido alkyl EVONIK 850 e RIES AG GERONOL® CF/AS Betaines, C12—I4- RHODIA INC alkyldimethyl (Cranberry, NJ) ORKLA INDIA PVT" BORRESPERSE® NA Lignosulfonate LTD (Vashi, India) MORWET® D425 Alkylnaphthalene sulfonate MONSON condensate COMPANIES, INC ATLOXTM 4913 . . CRODA WEST Non Ionic comb polymer_ Chino Hills, CA METASPERSETM Modified e acryllc" . - 3 500L CRODA WEST polymer P I . INTERNATIONAL 0 ymeric AGRIMER® AL 1 O Alkylated Vinylpyrrolidone LTY copolymers PRODUCTS , NJ) CEVOL® 205 . CELANESE LTD.

Polyvmyl alcohol (Dallas, TX) . AKZONOBEL ALCOSPERSE® 725 E pHgdgzlihgt’gany dy y CHEMISTRY LLC 1,2—propanediol, Alcohol TACTICTM LOVELAND ethoxylate, silicone polycther PRODUCTS INC. copolymer *EO : moles of ethylene oxide reacted with a particular hydrophobe **POE : moles ofpropylene oxide d with a particular hydrophobe The methods disclosed herein utilize the transformation—enhancing properties surfactants to dramatically increase transformation efficiency in plants such as immature maize embryos by Agrobacz‘erium (e.g., Agrobacterium tumefaciens). The surfactants used with the methods described herein are selected, as suggested above, based upon the ability to promote cell-cell interactions that will enhance transformation efficiency. The concentration of tant in the liquid medium can be 0.001 weight percent to 0.08 weight percent, 0.001 weight percent to 0.07 weight percent, 0.001 weight percent to 0.06 weight percent, 0.001 weight percent to 0.05 weight percent, 0.001 weight percent to 0.04 weight percent, 0.001 weight percent to 0.035 1001685931 weight percent, 0.001 weight t to 0.03 weight percent, 0.001 weight percent to 0.025 weight percent, 0.001 weight t to 0.02 weight percent, 0.001 weight percent to 0.015 weight percent, 0.001 weight percent to 0.01 weight t, or 0.005 weight percent to 0.01 weight percent.

One or more additional surfactants can also be used with the methods described herein. As indicated, the transformation efficiency is ent on a variety of factors ing plant species and —type and Agrobacterium strain. Given the variety of interactions involved, a system of two or more surfactants can provide enhanced transformation efficiency.

The additional surfactants used in a system of two or more surfactants can be ed, for example, from Table 1.

The methods described herein are broadly applicable to a variety of plant species varieties including monocotyledons and dicotyledons. Crops ofinterest include but are not limited to maize, rice, soybeans, canola, sunflower, alfalfa, sorghum, wheat, cotton, s, tomatoes, potatoes, and the like. The methods herein can be used with cells at s stages of pment, e.g., immature embryos. Thus, the methods described herein can be used to transform maize re embryos. The size ofimmature embryos used in the methods described herein can vary. For example, immature embryos can be greater than or equal to 1.5 mm and less than or equal to 2.5 mm in length.

The external environment the cells are ined in after exposure to Agrobaclerium according to the methods described herein can be controlled. For example, temperature, pH, and other components of growth medium the cells are placed upon after transformation according to the methods described herein can be varied and are generally well known to those of skill in the art. One ofthose variables is exposure to light. The methods bed herein can include exposing the plant cells to common 18 hour light/6 hour dark protocols or alternatively to continuous light after exposure to the Agrobacterium cells. For example, cells treated according to the methods described herein can be exposed to 24-hour white fluorescent light conditions weeks after treatment, e.g., until the regeneration and plantlet isolation stages of plant preparation.

An additional method includes preparing a liquid medium containing a surfactant, suspending Agrobacterium cells in the liquid , and exposing plant cells to the Agrobacterium cells in the liquid medium containing the surfactant. The Agrobacterium cells 1001685931 can be scraped from a solid medium prior to being suspended in the liquid medium containing tant. Additionally, the Agrobacterz'um cells can be grown in a liquid growth medium prior to being ded in the liquid medium containing a surfactant. ols and s for transforming plants using Agrobacterium are well known to those of skill in the art of molecular biology. Any types of methods known for the use of Agrobacterium in orming plants can be used with the methods described . The examples below provide embodiments of methods demonstrating the effectiveness of the methods described herein, but are not ed to be limitations on the scope of the claims.

All patents, patent applications, provisional applications, and publications referred to or cited herein are incorporated by reference in their entirety to the extent they are not inconsistent with the explicit teachings of this specification.

EXAMPLES The following examples illustrate procedures for practicing the claims. The examples and embodiments described herein are for illustrative purposes only and various modifications or changes in light thereof will be suggested to persons skilled in the art and are to be included within the spirit and scope ofthe claims. All percentages are by weight and all solvent mixture proportions are by volume unless otherwise noted. All temperatures are in degrees Celsius.

EXAMPLE 1. Agrobacterz‘um transformation for generation of superbinary vectors.

The Agrobacterium superbinary system is conveniently used for transformation of monocot plant hosts. Methodologies for constructing and validating superbinary vectors are well sed and incorporated herein by reference (Operating Manual for Plasmid pSBl, Version 3.1, available from Japan Tobacco, Inc., Tokyo, Japan). Standard molecular biological and microbiological methods were used to generate superbinary plasmids. Verification/validation of the structure of the inary plasmid was done using methodologies as ted in the Operating Manual for Plasmid pSBl. cterium strains harboring various superbinary plasmids were used in this work. All these plasmids ned, as the selectable marker/herbicide tolerance gene, the coding ce (CBS) for the AADl protein (US. Patent 7,838,733), whose expression was under the transcriptional control of a rice actinl promoter and associated intron 1, essentially as 1001685931 disclosed in U.S. Patent No. 5,641,876 and GENBANKTM Accession No. EU155408.1.

Termination of transcription and polyadenylation of the aad] mRNAs were determined by a maize lipase 3'UTR, essentially as disclosed as bases 921 to 1277 of GENBANKTM Accession No. gb]L359l3.1[MZELIPASE and in U.S. Patent No. 7,179,902. In on, the inary plasmids harbored a gene whose expression was not expected to affect transformation frequency.

In particular, in plasmid pEP81083, a CDS encoding a YFP protein (essentially as disclosed in US Patent No. 7,951,923) (transcription of which was controlled by a maize ubiquitin 1 promoter with associated intron 1; U.S. Patent No. 5,510,474), and whose mRNAs were terminated by a maize Per5 3'UTR (U.S. Patent No. 6,384,207» was advantageously used as a visual marker to monitor transformation and determine relative transformation efficiencies. Other superbinary plasmids used to ify the methods disclosed here (plasmids pEPSlOl3, l8, pEPS 1028, pEPSlOB6, pEPSlO38, pEP81059, pEPSlO64, pEP81066, pEPS1068, pEPS6004, and pEPS6008) harbored a CDS encoding a Dow AgroSciences etary protein, expression of which was controlled by the same transcription/termination elements as were used for the YFP CDS.

Expression onFP was used to measure the efficiency oftransformation in some experiments. ormation efficiency percentages were calculated as the number of calli that displayed sion of YFP, divided by the number oftreated embryos, times 100. YFP expression was ed by visual observation using either an Olympus SZX12 us America Inc; Center Valley, PA) or a Leica M165FC (Leica Microsystems Inc.; Buffalo Grove, IL) fluorescent microscope, with YFP filters covering the ranges for excitation at 5 14 nm and emission measured at 527 run.

In other experiments that employed Agmbacterz’um strains ing superbinary ds lacking the YFP gene, transformation efficiencies were calculated following ® analysis (Life Technologies; Carlsbad, CA) of progeny plants ed from embryos that were selected by means of resistance to Haloxyfop. The TAQMAN® components used were specific for the aad] coding region. Transformation efficiencies were calculated from the number of TAQMAN®~positive events determined, divided by the number of treated embryos, times 100. An "event" for these purposes was considered to be an embryo that ed one or more TAQMAN®-verified plant(s). An individual embryo was considered to be one event regardless of how many plants it may have produced. 1001685931 EXAMPLE 2. Transformation of maize by Agrobacterz'um strains (Transformation Protocol 1).

The basic work flow is summarized as s. Embryos are extracted from immature ears of corn at the developmental stage at which the young embryos are about 1.4 to 1.9 mm in length. When different transformation ions are to be compared, approximately equal numbers of embryos isolated from a single ear are divided amongst all the treatments. The embryos are incubated with a suspension containing cterium cells and surfactant (or not, for comparison), then are moved to solid—medium plates and co—cultivation is allowed for 3 to 5 days. The d embryos are transferred onto a medium containing antibiotics (for the suppression and killing of the Agrobacterz'um cells) and compounds for the selective isolation of genetically transformed corn tissues and plants. The corn tissue (usually, but not limited to, ) is grown on ion medium until plants are regenerated. These plants are tested to confirm their genetic transformation and those having a desired modification are grown to maturity for seed tion.

Immature Embryo Production Seeds from a B 104 inbred were planted into on— pots ning SUNSHINE CUSTOM BLEND 160 (SUN GRO HORTICULTURE; Bellevue, WA). The plants were grown in a greenhouse using a combination of high pressure sodium and metal halide lamps with a 16:8 hour Light:Dark photoperiod. To obtain immature embryos for transformation, controlled sib—pollinations were performed. Immature embryos were isolated at to 13 days post—pollination when embryos were approximately 1.4 to 1.9 mm in size. Maize ears were surface sterilized after ng the husks and silks by immersing in 50% commercial bleach (CLOROX®, 5.25% sodium hypochlorite) with TWEEN®—20 (1 or 2 drops per 500 mL) for 10 minutes and triple—rinsed with sterile water.

Immature embryos were aseptically isolated directly into a micro centrifuge tube containing 2 mL of Infection Medium with suspended Agrobacterz‘um cells, and surfactant as appropriate. The embryos were incubated with the suspension bacterium cells, ning surfactant (or not, for control experiments), for 5-30 minutes.

A suspension ofAgrobacterium cells containing a superbinary vector was prepared by first growing the cells as a lawn for 4 days at 25°, or 3 days at 28°, on solid agar plates containing YEP (gm/L: Yeast Extract, 5; Peptone, 10; NaCl, 5; agar, 15) with 50 mg/L 5931 Spectinomycin; 10 mg/L Rifampicin; and 50 mg/L omycin. (In some experiments, the Agrobacterium cells were grown on solid LB medium (SIGMA ALDRICH; St. Louis, MO) 20 gm/L, with antibiotics as above.) This e was ed from a single colony isolate established under the same conditions. One or two loopfuls of cells were d from the lawn, then uniformly resuspended (by gently pipetting up and down) in Infection Medium (IflVI) to an optical density at 600 nm (OD600) of 0.35 to 0.45. Infection Medium contains: 4.33 gm/L MS salts; IX ISU Modified MS Vitamins; 68.4 gm/L e; 36 gm/L glucose; 700 mg/L L-proline; 3.3 mg/L Dicamba—KOH; and 100 pM acetosyringone (prepared in DMSO); at pH 5.2.

Depending upon the experiment, an appropriate amount of surfactant solution (e. g. BREAK— THRU® S 233 at 0.01% final concentration) was added to the ion Medium after suspending the cells.

The Agrobacterium and embryo solution was incubated for 5 to 30 minutes at room temperature, and then the embryos were transferred to Co—cultivation Medium, which contained 4.33 gm/L MS salts; 1X ISU Modified MS Vitamins; 30 gm/L e; 700 mg/L L—proline; 100 mg/L myo-inositol; 3.3 mg/L Dicamba—KOH; 100 mg/L Casein Enzymatic Hydrolysate; 15 mg/L AgNO3; 100 uM acetosyringone; and 3 gm/L GELZANTM; at pH 5.8. Co-cultivation incubation was for 3 to 4 days at 250 under 24~hour white fluorescent light (approximately 50 pEm"2s'I).

Resting and Selection After co—cultivation, the embryos (36 embryos/plate) were carefully transferred to fresh non—selection Resting Medium containing 4.33 gm/L MS salts; 1X ISU Modified MS Vitamins; 30 gm/L sucrose; 700 mg/L L—proline; 3.3 mg/L Dicamba in KOH; 100 mg/L myo—inositol; 100 mg/L Casein Enzymatic Hydrolysate; 15 mg/L AgNO3; 0.5 gm/L MES; 250 mg/L Carbenicillin; and 2.3 gm/L GELZANTM; at pH 5.8. Incubation was continued for 7 days at 280 in 24~hour white fluorescent light (approximately 50 ‘l).

Following the 7 day resting period, the embryos were transferred to Selection Medium. For selection of maize tissues transformed with a superbinary plasmid containing plant expressible aad] able marker gene, the embryos (36/plate) were first transferred to Selection Medium I, which comprised Resting Medium (above) containing 100 nM R-Haloxyfop acid (0.0362 mg/L). The embryos were incubated for 1 week (28°; continuous light), and then transferred to ion Medium 11 which comprised g Medium with 500 nM R-Haloxyfop acid (0.1810 mg/L), on which they were incubated under continuous light for an additional 7 1001685931 days. At this time they were moved to fresh Selection Medium 11 and incubation was continued as above for an additional week.

Those skilled in the art of maize transformation will understand that other methods selection of transformed plants are available when other plant expressible selectable marker genes (e.g. herbicide tolerance genes) are used.

Pre-regeneration Following the selection process, cultures were transferred to Pre— regeneration Medium containing 4.33 gm/L MS salts; 1X ISU Modified MS Vitamins; 45 gm/L sucrose; 350 mg/L L—proline; 100 mg/L myO—inositol; 50 mg/L Casein Enzymatic Hydrolysate; 1.0 mg/L AgNO3; 0.25 gm/L MES; 05 mg/L aleneacetic acid in NaOH; 2.5 mg/L ic acid in ethanol; 1 mg/L 6—benzylaminopurine; 250 mg/L Carbenicillin; 2.5 gm/L GELZANTM; and 500 nM R—Haloxyfop acid; at pH 5.8. Incubation was ued for 7 days at 280 under continuous white fluorescent light as above.

Regeneration and plantlet ion For regeneration, the cultures were transferred to Regeneration Medium I containing 4.33 gm/L MS salts; 1X ISU Modified MS Vitamins; 60 gm/L e; 100 mg/L myo—inositol; 125 mg/L Carbenicillin; 2.5 gm/L GELZANTM; and 500 nM R—Haloxyfop acid; at pH 5.8 and plantlets were d to generate and grow at 280 under continuous white fluorescent light for up to 3 weeks.

When ets reached a suitable growth stage, they were excised with a forceps and scalpel and transferred to Regeneration Medium 11 containing 4.33 gm/L MS salts; IX ISU Modified MS Vitamins; 30 gm/L sucrose; 100 mg/L myo—inositol; 3.0 gm/L TM; at pH .8; and incubated at 280 under continuous white fluorescent light as above to allow for further growth and development of the shoot and roots.

Seed production Plants were transplanted into METRO-MIX 360 soilless growing medium (SUN GRO HORTICULTURE; BELLEVUE, WA) and hardened—off in a growth room.

Plants were then transplanted into SUNSHINE CUSTOM BLEND 160 soil mixture and grown to flowering in the ouse. Controlled pollinations for seed production were conducted.

EXAMPLE 3. ormation of maize by Agrobacterium strains formation Protocol 2).

The basic work flow is summarized as follows. Embryos are extracted from immature ears of corn at the developmental stage at which the young embryos are about 1.8 to 1001685931 2.4 mm in length. When different transformation conditions are to be compared, approximately equal numbers of embryos isolated from a single ear are divided amongst all the treatments. The embryos are incubated with a suspension containing Agrobacterium cells and surfactant (or not, for comparison), then are moved to solid-medium plates and co-cultivation is d for 1 to 4 days. The d embryos are erred onto a medium containing antibiotics (for the suppression and killing of the Agrobacterz'um cells) and compounds for the selective ion of genetically transformed corn tissues and plants. The corn tissue ly, but not limited to, callus) is grown on selection medium until plants are regenerated. These plants are tested to confirm their genetic transformation and those having a desired modification are grown to maturity for seed production. re Embryo Production Seeds from maize inbred line B104 (an Iowa State variety commercially released in the early 1980’s) were d into 4—gallon—pots ning SUNSHINE CUSTOM BLEND 160 (SUN GRO HORTICULTURE; Bellevue, WA). The plants were grown in a greenhouse using a combination of high pressure sodium and metal halide lamps with a 16:8 hour Dark photoperiod. To obtain immature embryos for transformation, controlled sib-pollinations were performed. Immature embryos were isolated at to 13 days post—pollination when embryos were approximately 1.8 to 2.4 mm in size. Maize ears were surface sterilized after removing the husks and silks by immersing in 50% cial bleach (CLOROX®, 6.15% sodium hypochlorite) with TWEEN®—20 (1 or 2 drops per 500 mL) for 10 minutes and triple—rinsed with sterile water.

Alternatively, maize ears can be surface sterilized by thorough spraying with a freshly prepared solution of 70% ethanol until the ear is completely soaked. Prior to use, the ear is allowed to air dry for half an hour in a sterile transfer hood to allow the ethanol solution tely evaporate.

Immature embryos were aseptically isolated directly into a micro centrifuge tube containing 2 mL of ation Medium with suspended Agrobacterium cells, and surfactant as appropriate. The embryos were incubated with the suspension ofAgrobacterium cells, containing surfactant (or not, for control experiments), for 5-30 minutes.

A suspension bacterium cells containing a superbinary vector was prepared by first growing the cells in 125 mL (in 500 mL baffled flask) of LB medium (SIGMA ALDRICH; St. Louis, MO) 20 gm/L, containing 50 mg/L Spectinomycin; 10 mg/L Rifampicin; 1001685931 and 50 mg/L Streptomycin with shaking (250 rpm in the dark) at 26° for 6 hr. This culture was established by 1:5 dilution of a 25 mL overnight culture (grown in the same medium) into the fresh medium. Cells were pelleted by fugation for 15 min at 3500 rpm at 4°, then uniformly resuspended (by gently pipetting up and down) in Inoculation Medium (InM) to an optical density of approximately 1.0 at 600 nm (OD600). Inoculation Medium contains: 2.2 gm/L MS salts (Frame el al. (2011, Genetic TransZormaz‘z‘on Using Maize Immature Zygptz'c Embryos.

I_n Plant Embryo Culture Methods and ols: s in Molecular Biology. T. A. Thorpe and E. C. Yeung, (Eds), Springer Science and ss Media, LLC. pp 327—341); 1X ISU Modified MS Vitamins (Frame et at, 2011 supra); 68.4 gm/L sucrose; 36 gm/L glucose; 115 mg/L L—proline; 100 mg/L ositol; and 200 uM acetosyringone (prepared in DMSO); at pH .4. Depending upon the ment, an appropriate amount of surfactant solution (e. g.

BREAK—THRU® S 233 at 0.01% final concentration) was added to the Inoculation Medium after suspending the cells.

The Agrobacterium and embryo solution was ted for 5 to 15 s at room temperature, and then the embryos were transferred to Co—cultivation Medium, which contained 4.33 gm/L MS salts; 1X ISU Modified MS Vitamins; 30 gm/L sucrose; 700 mg/L L—proline; 3.3 mg/L Dicamba in KOH (3,6—dichloro~o—anisic acid or 3,6—dichloro—2—methoxybenzoic acid); 100 mg/L myo—inositol; 100 mg/L Casein Enzymatic Hydrolysate; 15 mg/L AgN03; 100 uM acetosyringone in DMSO; and 3 gm/L GELZANTM (SIGMA—ALDRICH); at pH 5.8. Co— cultivation incubation was for 3 to 4 days at 25° under continuous white fluorescent light (approximately 50 pEm'Zs‘l).

Resting and Selection After co—cultivation, the embryos (36 s/plate) were carefully erred to non—selection Resting Medium containing 4.33 gm/L MS salts; 1X ISU Modified MS Vitamins; 30 gm/L sucrose; 700 mg/L L—proline; 3.3 mg/L Dicamba in KOH; 100 mg/L myo—inositol; 100 mg/L Casein Enzymatic Hydrolysate; 15 mg/L AgN03; 0.5 gm/L MES (2—(N—morpholino)ethanesulfonic acid monohydrate (PHYTOTECHNOLOGIES LABR.; Lenexa, KS); 250 mg/L icillin; and 2.3 gm/L TM; at pH 5.8. Incubation was continued for 7 days at 28° in continuous white fluorescent light conditions as above.

Following the 7 day resting period, the embryos were transferred to Selection Medium. For selection of maize tissues transformed with a superbinary plasmid containing plant expressible aad] selectable marker gene, the embryos (18 embryos/plate) were first 5931 transferred to Selection Medium I which ted of the Resting Medium (above), and containing 100 nM R-Haloxyfop acid (0.0362 mg/L). The embryos were incubated for 1 week, and then erred (12 embryos/plate) to Selection Medium 11, which consisted of Resting Medium ), and with 500 nM R-Haloxyfop acid (0.1810 mg/L), on which they were ted for an additional 2 weeks. Transformed isolates were obtained over the course of approximately 4 to 6 weeks at 28° under 24-hour white fluorescent light conditions (approximately 50 uEm‘Zs‘l). Recovered isolates were transferred to fresh Pre—Regeneration medium for initiation of regeneration and timber analysis.

Those skilled in the art of maize ormation will understand that other methods of ion of transformed plants are available when other plant expressible selectable marker genes (e.g. herbicide tolerance genes) are used.

Pre—regeneration Following the selection process, cultures exposed to the 24—hour light regime were transferred (6 to 8 calli/plate) to Pre—regeneration Medium containing 4.33 gm/L MS salts; 1X ISU Modified MS Vitamins; 45 gm/L sucrose; 350 mg/L L-proline; 100 mg/L myo—inositol; 50 mg/L Casein Enzymatic ysate; 1.0 mg/L AgNOg; 0.25 gm/L MES; 0.5 mg/L naphthaleneacetic acid in NaOH; 2.5 mg/L abscisic acid in ethanol; 1 mg/L 6- benzylaminopurine; 250 mg/L Carbenicillin; 2.5 gm/L GELZANTM; and 500 nM xyfop acid; at pH 5.8. Incubation was continued for 7 to 14 days at 28° continuous white fluorescent light (approximately 50 uEm"2s'1).

Regeneration and plantlet isolation For regeneration, the es were transferred (up to 12 calli per PHYTATRAYTM (PHYTOTECHNOLOGIES LABR.)) to a primary Regeneration Medium containing 4.33 gm/L MS salts; 1X ISU Modified MS Vitamins; 60 gm/L sucrose; 100 mg/L myo—inositol; 125 mg/L Carbenicillin; 3.5 gm/L GELLAN GUM G434 TECHNOLOGIES LABR.); and 500 nM R—Haloxyfop acid; at pH 5.8 and plantlets were allowed to te and grow for up to 3 weeks.

When plantlets reached 3 to 5 cm in length, they were transferred (6 plants per PHYTATRAYTM) to Plant Growth Medium containing 4.33 gm/L MS salts; 1X ISU Modified MS Vitamins; 30 gm/L sucrose; 100 mg/L myo-inositol; 3.5 gm/L GELLAN GUM G434; and 0.5 mg/L indoleacetic acid in NaOH; at pH5.8, and incubated at 25° under 16-hour white fluorescent light conditions (approximately 50 uEm‘Zs’l) to allow for further growth and development ofthe shoot and roots. 1001685931 Seed production Plants were transplanted into METRO-MIX 360 soilless g medium (SUN GRO HORTICULTURE; UE, WA) and hardened-off in a growth room. Plants were then transplanted into SUNSHINE CUSTOM BLEND 160 soil mixture and grown to flowering in the greenhouse. Controlled pollinations for seed production were conducted.

EXAMPLE 4. Transformation efficiencies using Agrobacz‘erium cells grown in liquid medium.

Agrobacterium superbinary strain LBA4404(pEPS 1083) was used to transform maize immature embryos by the method disclosed in Example 2 (Transformation Protocol 1).

Comparisons were made of the transformation efficiencies obtained when the A grobacterium cells were scraped from YEP agar plates and resuspended in Infection Medium (HM), versus experiments done at the same time using cterium cells grown in liquid medium LB, harvested by centrifugation and resuspended in 11M.

, Comparative ormation efficiencies were determined at various stages of the s by ng the s of yellow fluorescent spots (YFP+) on treated tissue pieces one to five weeks after initiation of the transformation experiments. Table 2 summarizes the results obtained.

Table 2. Comparison of transformation efficiencies using Agrobacterium inocula prepared from cells scraped from LBA4404(pEPSlO83} agarplates or harvested after grthh in liquid culture.

Experiment Stage of Agra. N0. of N0. of Number YFP Count Growth Embryos Treated YFP+ Calli (%) Plate 108 40/108 (37) Selection 1 Liquid 103 103/103 (100) Medium I Plate 108 66/108 (61) Liquid 36 36/36 (100) Plate 76 0/76 (0) 2 Pre—Regeneration Liquid 83 32/83 (39) Medium L Plate 107 L 0/107 (0) Liquid—1 100 18/100(18) 1 Plate 71 4 0/71 (0) 3 Pre-Regeneration L Liquid 4 72 1; 26/72 (36) Medium 4 Plate 1. ‘1 91 0/91 (0) Liquid 78 7/78 (9) , Plate 73 _1 4/73 (5) 4 Riga???“ '— Liquid 97 L 51/97 (53) Plate 3 69 1_ 3/69 (4) 1001685931 Liquid 59 36/59 (61) The results summarized in Table 2 demonstrate that infection of maize embryos using Agrobacterz'um cells freshly harvested from liquid culture provides significantly higher transformation efficiencies than is obtained using cells scraped from agar plates.

E 5. Improvement oftransformation efficiencies by addition of surfactant to Transformation Protocol 1.

Agra/bacterium superbinary strain LBA4404(pDAB108652) was used to transform maize re embryos by the methods disclosed in Example 2. Plasmid pDABlO8652 contains the YFP coding region, whose expression was driven by the ZmUbil promoter, and also harbors the am]! herbicide tolerance coding region under expression control ofthe rice actinl promoter. Comparisons were made of the transformation efficiencies obtained when the Agrobaclerium cells were suspended in HM g surfactant, versus experiments done at the same time with lfiVI containing added surfactant BREAK—THRU® S 233 at various concentrations. ormation efficiencies were calculated by counting calli with fluorescent s (each callus arising from a single embryo) after 4 weeks of Haloxyfop selection. At this time, the cent sectors were large and therefore the tissues represented stably transformed sectors. The results summarized in Table 3 demonstrate that use of surfactant increases transformation efficiencies, and that there is a sensitivity of the enhancing effect on the concentration of tant used.

Table 3. Effect of s concentrations of surfactant BREAK~THRU® S 233 transformation efficiencies.

Experiment Surfactant No. Embryos Plasmid Transformation Number Concentration Treated Efficiency (%) 1 pDAB108652 0% 245 2.86% :i _] 0.005% 126 l— 14.29% 0.01% 129 8.53% 2 —i_pDAB108652_'_ _J 0% _[ _] 272 0.74% [_ 0.02% 135 l_ f 6.67% |_ 0.04% 140 0% cterz'um inary strain LBA4404(pEPS 1083) was used to transform maize immature embryos by the method disclosed in Example 2. Comparisons were made ofthe 5931 transformation efficiencies obtained when the Agrobacterium cells were suspended in IflVI lacking surfactant, versus experiments done at the same time in the presence of added surfactant in the HM. Comparative ormation efficiencies were determined at various stages of the process by counting the s of yellow fluorescent spots (YFP+) on treated tissue pieces one to five weeks after initiation of the transformation experiments. Table 4 summarizes the results obtained.

In some experiments, the Agrobacterium cells were washed with IflVl (with, or without, surfactant) before the cocultivation step by suspension and gentle centrifugation ("wash" in Table 4). Further, in ment 5 (Table 4) 200 uM acetosyringone, (rather than 100 pM as is specified in Example 2) was used to induce vir gene expression, and the Agrobacterz'um cells were grown on a plate of LB medium with appropriate antibiotics, rather than YEP medium.

Table 4. Enhancement of transformation efficiency by Agrobaclerium through the use of a surfactant. Surfactants BREAK-THRU® S 233, PREFERENCE® or TM were added to the Infection Medium (working concentration 0.01%) used to create a suspension of Agmbacterium cells prior to co—cultivation.

No. of No. of % of EXP StagCeOolifFP Treatment Embryos Embryos s d YFP+ YFP+ No surfactant i 50 28 56 l Resting Medium S 233* 48 33 69 PREFERENCE® i 48 29 60 Selection No surfactant 60 10 17 Medium 1 S 233 60 39 65 No surfactant 64 20 31 Selection S 233 + lfM wash** 6O 44 73 Medium 1 HM + S 233 wash 66 24 36 S 233 + S 233 wash 72 55 76 No surfactant 36 0 0 Selection 8 233 + HM wash 4 _|_ 36 4 T_ 11 Medium 1 HM + S 233 wash 36 8 22 S 233 + S 233 wash 36 19 53 [_ No. of No. of % of EXP Stafifo‘l’lfanP Treatment Embryos Calli Embryos Treated YFP+ YFP+ 1001685931 Medium II S 233 60 29/46 48 n--—3 Medium 11 S 233 193 15/78 No surfactant 132 Pre~Regeneration S 233 110 Medium TACTICTM 114 * S 233 is THRU® S 233 ** IfM is Infection Medium used to suspend and/or wash the Agrobacterium cells.

*** The Agrobacterz’um cells were grown on an LB medium plate with antibiotics and vir gene sion was induced with 200 uM acetosyringone.

The experiments summarized in Table 4 y show that the presence of surfactant BREAK—THRU® S 233 in the Infection Medium used to re—suspend the Agrobacterium cells scraped from solid medium plates dramatically increases the transformation efficiencies of re embryos. Further, tant TACTICTM has a positive but less dramatic effect on enhancing transformation efficiency.

In a r ification ofthe methods of this disclosure, immature maize embryos were transformed with cells ofAgrobacterium strain LBA4404(pEPSlO83) by the methods of Example 2. Transformation efficiencies were monitored by the appearance of YFP+ spots or sectors on developing calli from immature embryos. The left side of Figure 1 shows five experiments (Experiments 1 to 5) using Agrobaclerium cells scraped from solid agar plates, and the right side of Figure 1 shows results from three experiments (Experiments 6 to 9) in which the Agrobacterium cells were harvested from liquid-grown cultures. In combined Experiments 1 through 5, transformation efficiencies were sed in s from all nine of the ears harvested (100%) and the transformation ency increases were statistically significant (Fisher's Exact p<—0.05) in embryos from six of the nine ears (67%). In combined Experiments 6 through 9 d grown Agrobacreria), embryos from all eight of the ears harvested (100%) showed a statistically significant increase in transformation efficiency. Thus, it is clear from the results summarized in Figure 1 that addition of BREAK-THRU® S 233 to the ion Medium dramatically increases transformation efficiencies of maize immature embryos, in some cases resulting in transformation efficiencies of over 90%.

In another illustration of the methods of this disclosure, immature maize embryos were transformed with cells ofAgrobacterium strain LBA4404 harboring various plasmids (all 1001685931 of which contained the aad] able marker gene) by the methods of Example 2. As before, the experimental treatments compared transformation efficiencies with, or without, the use of 0.01% surfactant BREAK—THRU® S 233. The embryos were regenerated and taken all the way through Haloxyfop selection to plant production. Thus, the data were collected at a substantially later stage than that summarized in Figure 1. Transformation efficiency percentages were ated by dividing the number of embryos that produced a transgenic plant ("an event") by the number of treated immature s, times 100. For this purpose, an embryo was counted as a single event even if it produced multiple transgenic plants. The results of three experiments using cz‘erz'um cells scraped from agar plates are shown in Figure 2 (Experiments 1, 2 and 3). In addition, Figure 2 shows the results of an ment (Experiment 4) in which the Agrobacterium cells were grown in liquid medium, harvested by centrifugation, and resuspended in [M (with, or without, BREAK—THRU® S 233). Paired bars in Figure 2 show the responses of embryos from individual ears.

It is clear from the data in Figure 2 that addition ofthe surfactant BREAK—THRU® S 233 results in a dramatic se in Agrobacterium—mediated transformation efficiencies of maize immature embryos, regardless of previous growth configuration of the cterium cells and regardless ofthe gene composition ofthe orming plasmid. In combined Experiments 1, 2, and 3, transformation efficiencies were increased in embryos from 23 of the 26 ears harvested (88%) and the transformation efficiency increases were statistically significant (Fisher's Exact p<—0.05) in embryos from 12 of the 26 ears (46%). In Experiment 4 (liquid growth Agmbacleria) embryos from 10 of the 12 cars harvested (83%) showed an increase in transformation efficiency, and the increase was statistically cant in one of the 12 ears (8%).

EXAMPLE 6. ison of transformation—enhancing action of surfactants of various chemical classes.

Table 1 provides a non—limiting list of surfactants of several chemical classes.

Transformation experiments of immature embryos were conducted using Transformation Protocol 2 as provided in Example 3. Agrobacterium cells harboring s plasmids were suspended in Inoculation Medium (InM) containing BREAK—THRU® S 233 or various other surfactants (all at a concentration of 0.01%), and transformation rates (measured by a ® assay of the curd] gene were compared 7 to 10 weeks after initiation of the experiment. 1001685931 ormation efficiency percentages were calculated by dividing the number of embryos that ed a transgenic plant ("an event") by the number of treated re embryos, times 100.

For this purpose, an embryo was counted as a single event even if it produced multiple transgenic plants. Table 5 presents the transformation efficiencies obtained.

Table 5. ison of transformation efficiencies obtained with surfactants of various chemical classes. BREAK—THRU® S 233 and other surfactants were used at a concentration of 0.01%.

No' Of Experiment . Transformation Plasmld Surfactant 4 Embryos ncy ( A1). 0 Treated BREAK-THRU® s 233 756 25 pBPS 1036 SILWET® H8429 498 4.1 BREAK—THRU® S 233 648 16.4 pEPS6008 AGNIQUE® 880-10 648 14.5 BREAK-THRU® s 233 648 15 pEPS 1066 SILWET® H8429 648 5 BREAK—THRU® s 233 647 14.4 ADSEE® AB—650 660 1.9 BREAK~THRU® s 233 534 23 pEPS6004 TRYCOL® 5941 540 15 BREAK-THRU® s 233 648 20 6 pEPS 1013 METASPERSE® SOOL 648 9 BREAK—THRU® s 233 390 16.3 7 pEPSlO64 UPTAKE® 324 5.6 BREAK—THRU® s 233 432 9 8 pEPs1018 ALCOSPERSE® 725 432 0 BREAK—THRU® s 233 427 23 9 pEPSlO38 GERENOL® CF/AS 30 432 27 BREAK—THRU® s 233 468 29 E13810” BREAK-THRU® s 233 408 11 —_pEPSlozg BREAK-THRU®SZ33_428 12 pEPSlO64 1001685931 * On e 4 ears were used in a given experiment. Embryos ted from a single ear were split between the two treatments in each ment.

The results summarized in Table 5 demonstrate that the use of BREAK—THRU® S 233, when included in the Inoculation Medium used to re—suspend the Agrobacrerz'um inoculum cells grown in and harvested from liquid medium, provided transformation ncies that were superior to those obtained with the majority of the other surfactants tested. In three experiments (Experiment 2, Experiment 9, and Experiment 11), the transformation efficiencies observed were nearly the same n the two surfactants.

EXAMPLE 7. ormation results from ent operators.

One d in the art of maize transformation will understand that plant transformation methodologies often require considerable expertise that is acquired over months or years of experimentation. Transformation efficiencies may vary over a wide range due to inconsistencies in the ways in which procedures are practiced by different operators. Thus, it is advantageous to provide maize transformation procedures that improve predictability in transformation efficiencies obtained by different operators at different times. ormations of maize immature embryos were performed over a period of several months using the s of Example 3 (Agrobacterium strain LBA4404 harboring various plasmids) and containing BREAK—THRU® S 233 in the Inoculation Medium. Transformation efficiencies were estimated from counts of Haloxyfop—tolerant callus tissues obtained. Table 6 summarizes the results obtained.

Table 6. Transformation efficiencies obtained by multiple operators using methods that incorporate surfactant in the Inoculation Medium.

Operator No. of . Estimated Standard Ears Used Trans Eff. % 7" Deviation 1001685931 0-18 -_-—— *From manual event counts — not all events were verified by Taqman® analysis. Escape rate for Haloxyfop selection is approximately 5%.

**Average ormation Efficiency for all operators.

The results summarized in Table 6. show that the transformation protocol disclosed in Example 3, when practiced with the inclusion ofBREAK—THRU® S 233 in the Inoculation Medium, provides a robust and predictable methodology that reduces operator—to operator variation in transformation efficiency. Further, the improved predictability of the methods allows a more accurate determination of the size of the experiment (6.g. s of embryos that must be treated) to obtain a desired e (e.g. numbers of transformed events obtained).

The t invention is not limited in scope by the embodiments disclosed herein which are intended as illustrations ofa few aspects ofthe invention and any embodiments which are functionally equivalent are within the scope of this invention. Various modifications of the methods in addition to those shown and bed herein will become apparent to those skilled in the art and are intended to fall within the scope of the appended claims. Further, while only certain representative combinations of the method steps disclosed herein are specifically discussed in the embodiments above, other combinations of the method steps will become nt to those skilled in the art and also are intended to fall within the scope of the appended claims. Thus a combination of steps may be explicitly mentioned herein; however, other combinations of steps are included, even though not explicitly stated. Where a value is explicitly recited, it is to be understood that values which are about the same quantity or amount as the recited value are also within the scope of the ion. Where a range of values is recited, each intervening integer value, and each fraction thereof, between the recited upper and lower limits of that range is also specifically disclosed, along with each sub-range between such . The term “comprising” and variations f as used herein is used synonymously with the term “including” and variations thereof and are open, non-limiting terms. As used , the terms “modify” or “alter”, or any forms thereof, mean to , alter, replace, delete, substitute, remove, vary, or transform. 1148 THE

Claims (15)

CLAIMS DEFINING THE INVENTION ARE AS S:
1. l. A method for plant cell transformation comprising ng immature embryo plant cells to Agrobacterium cells in a liquid medium containing a non—ionic trisiloxane surfactant, the surfactant having a concentration of 0.001 weight t to 0.08 weight percent in the liquid medium, and wherein the non—ionic trisiloxane surfactant is not a trisiloxane alkoxylate.
2. 2. The method for plant cell transformation of claim 1, r comprising an additional surfactant.
3. 3. The method for plant cell transformation of claim 2, n the additional surfactant is an adjuvant, a non—ionic surfactant, an anionic surfactant, an oil based surfactant, an amphoteric surfactant, or a polymeric surfactant.
4. 4. The method for plant cell transformation of any one of claims 1 to 3, wherein the plant cells are maize cells.
5. 5. The method for plant cell transformation of any one ofclaims 1 to 4, wherein the immature embryos are greater than or equal to 1.5 mm and less than or equal to 2.5 mm in length.
6. 6. The method for plant cell transformation of any one ofclaims l to 5, wherein the plant cells are exposed to continuous light after exposure to the Agrobaclerium cells.
7. 7. A method for plant cell ormation comprising: ing a liquid medium containing a non—ionic trisiloxane surfactant, wherein the non— ionic trisiloxane surfactant is not a trisiloxane alkoxylate and wherein the non—ionic surfactant has a concentration of 0.001 weight percent to 0.08 weight percent in the liquid medium; suspending Agrobacterz‘um cells in the liquid medium; and exposing immature embryo plant cells to the Agrobacterium cells in the liquid medium containing the surfactant. l 001 684940
8. 8. The method for plant cell transformation of claim 7, wherein the Agrobacterium cells are d from a solid medium prior to being suspended in the liquid medium containing a surfactant.
9. 9. The method for plant cell transformation of claim 7, wherein the Agrobacterz‘um cells are grown in a liquid growth medium prior to being suspended in the liquid medium containing a surfactant.
10. 10. The method for plant cell ormation of any one of claims 7 to 9, further comprising an onal surfactant.
11. 1 l. The method for plant cell transformation of claim 10, wherein the additional surfactant is an adjuvant, a non—ionic surfactant, an anionic surfactant, an oil based surfactant, an amphoteric surfactant, or a polymeric surfactant.
12. 12. The method for plant cell transformation of any one of claims 7 to l 1, wherein the plant cells are maize cells.
13. 13. The method for plant cell transformation of any one of claims 7 to l 1, wherein the immature embryos are 1.5 to 2.5 mm in length.
14. 14. The method for plant cell transformation of any one of claims 7 to 13, wherein the plant cells are exposed to uous light after re to the Agrobacterium cells.
15. 15. The method for plant cell transformation ofclaim l or 7, substantially as hereinbefore described. ;FLIZQIXZ LIZQIXZ Ln Experiment