EP0789773A1

EP0789773A1 - Processes for modifying plant flowering behaviour

Info

Publication number: EP0789773A1
Application number: EP95938378A
Authority: EP
Inventors: Georg Leggewie; Jörg Riesmeier; Wolf-Bernd Frommer
Original assignee: Hoechst Schering Agrevo GmbH
Current assignee: Bayer CropScience AG
Priority date: 1994-10-31
Filing date: 1995-10-30
Publication date: 1997-08-20
Also published as: WO1996013595A1; HUT77471A; CA2204023A1; HU221005B1; US6025544A; DE4439748A1; AU701718B2; JPH10507920A; AU3979495A

Abstract

The invention concerns processes for growing plants whose flowering behaviour is modified in comparison with wild plant species, in particular for growing plants which flower early and to an increased extent. The invention also concerns the resultant plants and the use of DNA molecules which code saccharose carriers in order to modify the plant flowering behaviour.

Description

Process for changing the flowering behavior in plants

The present invention relates to processes for the production of plants with a different flowering behavior compared to wild-type plants, in particular premature flowering and increased flowering, and to the plants obtainable from the process. Such plants are produced by increasing the sucrose transporter activity in the plants. The invention further relates to the use of DNA molecules which encode sucrose transporters to change the flowering behavior in plants.

The formation of flowers in plants is a prerequisite for sexual reproduction and is therefore essential for the multiplication of plants which cannot be propagated vegetatively, and for the formation of seeds and fruits. The point in time at which plants pass from purely vegetative growth to flower formation is of central importance, for example in agriculture, gardening and plant breeding. Likewise, the number of flowers is often of economic interest, e.g. in the case of various useful plants (tomato, cucumber, zucchini, cotton, etc.) in which a higher number of flowers may mean a higher yield, or in the production of ornamental plants and cut flowers.

In many areas of application, early flowering of the plants is advantageous. In agriculture, for example, early flowering of various crop plants would allow a shortening of the time between sowing and harvesting and thus the spreading of two sowings per year or an extension of the period between flowering and harvesting, which may result in an increase in yield . Can also be used in plant breeding premature flower formation contributes to a considerable shortening of the breeding process and thus brings about an improvement in economy. The economic benefits of early flowering are also evident for horticulture and ornamental plant production. The efforts to date to elucidate the mechanisms which determine the time of flower formation in plants do not allow a clear conclusion to be drawn about the factors involved and the decisive factors. For a number of plants it is known that environmental influences determine the transition between vegetative growth and flower formation, for example light / dark rhythms, temperature and water supply. How these stimuli are absorbed by the plant and converted into physiological signals that induce flower formation in the apical meristem is largely unknown. Various theories are discussed and a whole series of possible factors are taken into account, such as, for example, flowering hormones (florigen / antiflorigen), carbohydrates, cytokinins, auxin, polyamines and calcium ions (Bernier et al., Plant Cell 5 ( 1993), 1147-1155).

The control of the time of flower formation by regulating exogenous stimuli, such as light / dark rhythm, temperature or water supply, can only be implemented in practice to a limited extent, for example in greenhouses. In order to achieve premature flower formation in plants that grow under field conditions, it is therefore necessary to use plants that show premature flower formation regardless of exogenous stimuli. Possibilities for producing such plants exist, on the one hand, in mutagenesis processes, which, however, cannot be used for all species, in breeding processes, which are, however, very time-consuming and have to be carried out separately for each plant species, or in genetic engineering Process. However, it is prerequisite for the applicability of a rule gentechni¬ process that are at their loci of a identifi ^¬ which have a substantial influence on the point BlühZeit-, and that the DNA sequences are available, the code the relevant products. So far, however, this has not been the case.

For the species Arabidopsis thaliana, on which most investigations on the regulation of the time of flowering have so far been carried out, various mutants have been described which bloom prematurely in comparison to wild type plants (see references in Lee et al., Plant Cell 6 (1994 ), 75-83), however, these mutants have not yet been characterized. The clarification of the biochemical causes leading to the premature flowering has also not yet been successful.

Bell et al. , Plant Mol. Biol. 23 (1993), 445-451) describe tobacco plants which have been transformed with the cdc2S cDNA from Schizosaccharomyces porπbe and which, as a result of the expression of this mitosis-inducing protein, cause premature flower formation and strong show increased number of flowers. However, these plants have the disadvantage that there are large changes in the leaf morphology. In particular, the leaves of these plants are rolled.

This process therefore does not appear to be suitable for producing useful plants which have changed their flowering behavior.

For the production of intact plants with a higher number of flowers per plant or an early flower formation one is therefore still dependent on the classic breeding methods or mutagenesis methods today.

The present invention is therefore based on the object of providing simple methods which make it possible to modify plants to the extent that their flowering behavior is changed, in particular in that they show premature flower formation and / or an increased flower set .

This object is achieved by providing the tentansprüchen in de ^'Pa¬ embodiments described. The invention therefore relates to the use of DNA molecules which encode proteins with the biological activity of a sucrose transporter to change the flowering behavior in plants.

The published PCT application WO 94/00574 describes DNA sequences which encode sucrose transporters from spinach and potato. This application also mentions the possibility of introducing these sequences in connection with DNA sequences for the regulation of transcription in plants with the aim of overexpressing such sucrose transporters. However, the use of DNA sequences which code for sucrose transporters to change the flowering behavior in plants has not been described. The sucrose transporter is assumed to play a central role in the transport of sucrose, the most important form of transport of the photoassimilates formed by photosynthesis, from the photosynthetically active tissues into the phloem. The extent to which it also plays a role in the transport of sucrose from the phloem into photosynthetically inactive tissues that rely on the import of photoassimilates (so-called "sink" organs) has so far been controversial (Riesmeier et al ., Plant Cell 5 (1993), 1591-1598; Riesmeier et al., EMBO J. 13 (1994), 1-7).

A function of sucrose transporters in regulating the flowering behavior had not previously been considered. Sucrose has been discussed several times as a potential signal for flower induction in the apical meristem (Bernier et al., Plant Cell 5 (1993), 1147-1155; Lejeune et al., Planta 190 (1993), 71-74; Lejeune et al ., Plant Physiol. Biochem. 29 (1991), 153-157), however, an influence of a sucrose transporter on the flowering behavior as a result of an increased activity of this transporter has so far not been known and was also not to be expected for various reasons. It was surprisingly found that a change in the flowering behavior can be observed in transgenic plants in which the activity of the sucrose transporter in the tissues was increased compared to non-transformed plants. In the context of this application, an increased activity of the sucrose transporter is understood to mean that the total sucrose transporter activity in the transgenic plants is increased, in particular by at least 30%, preferably by at least 50%, particularly preferably by, in comparison with non-transformed plants at least 100%, and in particular by at least 200%. Sucrose transporters are understood to be proteins that are able to transport sucrose across biological membranes. The activity of such transporters can be according to the Riesmeier et al. (EMBO J. 11 (1992), 4705-4713) determine the method described. A changed flowering behavior is understood in the context of this application that premature flowering and flowering take place in transformed plants compared to non-transformed plants a), prematurely meaning that the transformed plants compared to wild-type plants at least a few days , preferably form and bloom flowers one to several weeks, in particular 1-2 weeks earlier, and / or b) show an increased flower set, which means that, compared to wild-type plants, the transformed plants produce on average more flowers per plant, generally use at least 5% more flowers, in particular 10-100% and preferably 10-40% more flowers.

An increase in sucrose transporter activity compared to wild-type plants can be achieved by introducing DNA molecules into plants which encode a sucrose transporter. This leads to additional synthesis of proteins with sucrose in the transgenic cells sea transporter activity. As a result of this, transformed tissues in which the introduced DNA molecule is expressed have an increased sucrose transporter activity compared to non-transformed cells.

In order to achieve an increase in the sucrose transporter activity in the tissues of plants, the coding region of a DNA sequence which codes for a sucrose transporter is preferably linked to DNA sequences which are required for transcription in plant cells, and in Plant cells introduced. The regulatory sequences required for the transcription are, on the one hand, promoters and possibly enhancer elements which are responsible for the initiation of the transcription. Furthermore, termination signals, which lead to the termination of the transcription and to the addition of a poly-A tail to the resulting transcript, can optionally be added. These sequences are linked to one another in such a way that the coding region of a sucrose transporter gene is connected in sense orientation to the 3 'end of the promoter, so that an mRNA is synthesized which converts into a protein with the activity of a sucrose transporter can be translated, and the termination signal is connected to the 3 'end of the coding region.

Furthermore, the coding region can be linked to sequences which increase translation in plant cells, as described in the examples.

The DNA molecules which code for a sucrose transporter can originate from any organism which contains such sequences, in particular from any prokaryotic or eukaryotic organism. In a preferred embodiment, the DNA molecules come from plants, fungi or bacteria. In plants, higher plants, in particular monocotyledonous or dicotyledonous plants, are preferred. DNA molecules that are saccharo- Coding transporters are already known from various organisms and are given below. These are preferably used in the context of the invention.

The invention also relates to a method for changing the flowering behavior in plants, in which the changed flowering behavior is brought about by increasing the activity of the sucrose transporter in plants.

The production of transgenic plants which have a different flowering behavior compared to non-transformed plants, in particular a premature flower formation and / or an increased flower set, is preferably carried out by a process which comprises the following steps: a) producing an expression cassette which comprises the following DNA sequences: i) a promoter which is functional in plant cells and which ensures the transcription of a subsequent DNA sequence, ii) at least one DNA sequence which codes a sucrose transporter and is sent to the 3 'in sense orientation End of the promoter is coupled, and iii) optionally a termination signal for the termination of the transcription and the addition of a poly-A tail to the resulting transcript which is coupled to the 3 'end of the coding region, b) transformation plant cells with the expression cassette produced in step a) and stable integration of the expressi on cassette in the plant genome, and c) regeneration of whole, intact plants from the transformed plant cells.

In principle, any promoter which is functional in plants is suitable for the promoter mentioned under i). For example, the 35S promoter of the Cauliflower mosaic virus (Odell et al., Nature 313 (1985), 810-812) is suitable, which ensures constitutive expression in all tissues of a plant and that in WO / 9401571 described promoter con structure. However, promoters can also be used which lead to an expression of subsequent sequences only at a point in time determined by external influences (see, for example, WO / 9307279) or in a certain tissue of the plant (see, for example, Hadash et al., Plant Cell 4 (1992), 149-159, Stockhaus et al., EMBO J. 8 (1989), 2245-2251).

The DNA molecules, which comprise a coding region for a sucrose transporter, can be of either native or homologous origin as well as foreign or heterologous origin with respect to the plant species to be transformed. Both DNA molecules derived from prokaryotic organisms and those derived from eukaryotic organisms, in particular plants, can be used. Prokaryotic sequences are known, for example, from E. coli (Bookman et al., Mol. Gen. Genet. 235 (1992), 22-32; EMBL library: accession number X63740). DNA molecules which encode vegetable sucrose transporters are preferably used. For example, RNA or DNA sequences from Arabidopsis thaliana (suc 1 and suc 2 genes; EMBL library: accession numbers X75365 and X75382, as well as H36128, H36415, R64756, T76707 and T42333), Solanum tuberosum (Riesmeier et al ., Plant Cell 5 (1993), 1591-1598; EMBL genebank: accession numbers X69165 and WO 94/00547), Plantago major (EMBL genebank: accession numbers X75764 and X84379), L. esculentum (EMBL genebank: access¬ number X82275), Nicotiana tabacum (EMBL gene bank: access numbers X82276 and X82277), R. co munis (EMBL gene bank: access number Z31561), B. vulgaris (EMBL gene bank: accession number X83850). and rice (EMBL library: accession numbers D40522 and D40515), which encode sucrose transporters. A particular embodiment of the present invention provides for the use of a DNA molecule from Spinacia oleracea which encodes a sucrose transporter (see also Riesmeier et al., EMBO J. 11 (1992), 4705-4713 and WO 94/00547). A further preferred embodiment of the method according to the invention provides that DNA molecules are used which encode sucrose transporters with the lowest possible I ^ value. Such a transporter activity is known, for example, from Candida albicans (Williamson et al., Biochem. J. 291 (1993), 765-771).

The molecules which encode sucrose transporters can be cDNA molecules as well as genomic sequences. The DNA molecules can be isolated from the corresponding organisms using the common techniques known to the person skilled in the art, for example hybridization or polymerase chain reaction, or they can be prepared synthetically.

The termination signals for transcription in plant cells mentioned under iii) are described and can be interchanged as desired. For example, the termination sequence of the nopaline synthase gene from AgroJbacεeriLim tumefaciens can be used (see e.g. Gielen et al., EMBO J. 8 (1989), 23-29). The expression cassette described can also contain DNA sequences which enhance the translation of the coding region in plant cells.

The method according to the invention can in principle be applied to any flower-forming plant species. It is preferably applied to the plants specified below.

The invention further relates to transgenic plants which, owing to the increased activity of the sucrose transporter, have a different flowering behavior compared to wild-type plants, in particular premature flowering and flowering and / or an increased flower set. Such transgenic plants are preferably obtainable by the process described above. This means that the increase in the sucrose transport Interactivity preferably on the fact that DNA molecules which encode a saccharose transporter are introduced and expressed in the plants. These are preferably DNA molecules that come from plants, fungi or bacteria.

The plants according to the invention are preferably monocotyledonous or dicotyledonous crops, for example cereals (such as barley, oats, rye, wheat etc.), maize, rice, vegetable plants (such as tomato, melon, zucchini etc.) , Cotton, rapeseed, soybean, types of fruit (such as plum, apple, pear etc.), ornamental plants or cut flowers.

To prepare the introduction of foreign genes into higher plants, a large number of cloning vectors are available which contain a replication signal for E. coli and a marker gene for the selection of transformed bacterial cells. Examples of such vectors are pBR322, pUC series, Ml3mp series, pACYC184 etc. The desired sequence can be introduced into the vector at a suitable restriction site. The plasmid obtained is used for the transformation of E. coli cells. Transformed E. coli cells are grown in a suitable medium, then harvested and lysed. The plasmid is recovered. Restriction analyzes, gel electrophoresis and other biochemical-molecular biological methods are generally used as the analysis method for characterizing the plasmid DNA obtained. After each manipulation, the plasmid DNA can be cleaved and linked to other DNA sequences. Each plasmid DNA sequence can be cloned in the same or other plasmids.

Plasmids are preferably used to transform plant cells using the expression cassette described in the method.

A variety of techniques are available for introducing DNA into a plant host cell. These techniques include the transformation of plant cells with T-DNA using Agrobacterium tumefaciens or Agrobacterium rhizogenes as transformation agent, the fusion of protoplasts, the injection, the electroporation of DNA, the introduction of DNA using the biolistic method and other possibilities.

When injecting and electroporation of DNA into plant cells, no special requirements are made of the plasmids used. Simple plasmids such as e.g. pUC derivatives can be used. However, if whole plants are to be regenerated from such transformed cells, the presence of a selectable marker gene is necessary.

Depending on the method of introducing desired genes into the plant cell, further DNA sequences may be required. E.g. If the Ti or Ri plasmid is used for the transformation of the plant cell, at least the right boundary, but often the right and left boundary of the Ti and Ri plasmid T-DNA as the flank region, must be linked to the genes to be introduced .

If agrobacteria are used for the transformation, the DNA to be introduced must be cloned into special plasmids, either in an intermediate vector or in a binary vector. Because of sequences which are homologous to sequences in the T-DNA, the intermediate vectors can be integrated into the Ti or Ri plasmid of the agrobacteria by homologous recombination. This also contains the vir region necessary for the transfer of the T-DNA. Intermediate vectors cannot replicate in agrobacteria. The intermediate vector can be transferred to Agrobacterium tumefaciens by means of a helper plasmid (conjugation). Binary vectors can replicate in E. coli as well as in Agrobacteria. They contain a selection ark gene and a linker or polylinker, which are framed by the right and left T-DNA border region. They can be transformed directly into the agrobacteria (Holsters et al., Mol. Gen. Genet. 163 (1978), 181-187). The agrobacterium serving as the host cell is said to be a plasmid which carries a vir region. The vir region is necessary for the transfer of the T-DNA into the plant cell. Additional T-DNA can be present. The agrobacterium transformed in this way is used to transform plant cells.

The use of T-DNA for the transformation of plant cells has been intensively investigated and is sufficient in EP 120516; Hoekema, In: The Binary Plant Vector System Offset- drukkerij Kanters B.V., Alblasserdam, Chapter V; Fraley et al., Crit. Rev. Plant. Sci., 4 (1985), 1-46 and An et al., EMBO J. 4 (1985), 277-287.

For the transfer of the DNA into the plant cell, plant explants can expediently be cultivated with Agrobacterium tumefaciens or Agrobacterium rhizogenes. Whole plants can then be regenerated from the infected plant material (e.g. leaf pieces, stem segments, roots, but also protoplasts or suspension-cultivated plant cells) in a suitable medium, which can contain antibiotics or biocides for the selection of transformed cells. The plants obtained in this way can then be examined for the presence of the introduced DNA.

Once the introduced DNA is integrated in the genome of the plant cell, it is generally stable there and is also retained in the progeny of the originally transformed cell. It normally contains a selection marker which gives the transformed plant cells resistance to a biocide or an antibiotic such as kanamycin, G 418, bleomycin, hygroycin or phosphinotricin and others. mediated. The individually chosen marker should therefore allow the selection of transformed cells from cells that lack the inserted DNA.

The transformed cells grow within the plant in the usual way (see also McCormick et al., Plant ^'' Cell Reports 5 (1986), 8-1-84). The resulting plants can are normally grown and crossed with plants that have the same transformed genetic makeup or other genetic makeup. The resulting hybrid individuals have the corresponding phenotypic properties. Two or more generations should be grown to ensure that the phenotypic trait is stably maintained and inherited. Seeds should also be harvested to ensure that the appropriate phenotype or other characteristics have been preserved.

Fig. 1 shows the plasmid pΩA7DE-S21-Myc8.

A = Fragment A: CaMV 35S promoter, nt 6909-7437 (Franck et al., 1980, Cell 21, 285-294). In the 5 'region of the promoter, two 35S enhancer elements (330 bp HincII / EcoRV fragment) were inserted into the Nco I interface.

B = fragment B: 73 bp Nco I / Asp 718 fragment (TMV-Ul) with the translation enhancer from the tobacco mosaic virus

C = fragment C: DNA fragment approx. 1600 bp long, which encodes nucleotides 70 to 1644 of the cDNA encoding the sucrose transporter from spinach (Riesmeier et al., EMBO J. 11 (1992), 4705-4713), includes

D = fragment D: 33 bp long DNA fragment which encodes the amino acid sequence EQKLISEEDLN-COOH

E = fragment E: termination sequence of the octopine synthase gene; nt 11748-11939 the T-DNA of the Ti plasmid pTiACH5 (Gielen et al., EMBO J. 3 (1984), 835-846)

Fragments A, B, C, D and E are in the vector pUC18. The plasmid has a size of approximately 5700 bp.

Fig. 2 shows the plasmid pΩ-S21.

A = Fragment A: CaMV 35S promoter, nt 6909-7437 (Franck et al., Cell 21 (1980) 285-294). In the 5 'region of the promoter, two 35S enhancer elements (330 bp HincII / EcoRV fragment) were inserted into the Nco I interface. B = fragment B: 73 bp Nco I / Asp 718 fragment (TMV-Ul) with the translation enhancer from the tobacco mosaic virus

The plasmid has a size of approximately 12.6 kb

Fig. 3 shows the plasmid p35 S-Ω-OCS

4 a and b show transformed tobacco plants in comparison with non-transformed tobacco plants.

a: Three plants of tobacco line 12, which had been transformed with the plasmid pΩ-S21 (rear) are shown in comparison with two non-transformed tobacco plants (front). The plants are approximately 128 days old and were kept in the phytotron.

b: Three plants of the tobacco line 32, which had been transformed with the plasmid pΩ-S21 (rear) are shown in comparison with two non-transformed tobacco plants (front). The plants are approximately 128 days old and were kept in the phytotron.

5 shows as a bar graph the average number of days between the transfer of the plants from the tissue culture into soil until the opening of the first flower. In each case 12 plants per genotype were grown in a plant growth chamber under the following light conditions. 7- 9 a.m. 300 μmol quantum m ² sec ^-1

9-11 a.m. 600 μmol quantum m ² sec ^_1

11 a.m. - 1 p.m. 900 μmol quantum m ² sec ^_1

1 pm-5pm 1200 μmol quantum m ² sec ^_1

5 - 7 p.m. 900 μmol quantum m ² sec ^_1

7 - 9 p.m. 600 μmol quantum m ² sec ^_1

9 pm-11pm 300 μmol quantum m ² sec ^"1

6 shows as a bar chart the average number of days between the transfer of the plants from the tissue culture into soil until the opening of the first flower. In each case 12 plants per genotype were grown in a plant growth chamber under the following light conditions. Lines 32, 12, 5 and 1 are 4 independent transgenic lines which had been transformed with the plasmid pΩ-S21. 7 am-11pm 400-500 μmol quantum m ^"2 sec ^_1

Fig. 7 shows a bar chart of the average number of leaf attachments until the flowers are formed. For experimental conditions, see FIG. 6.

Media and solutions used in the examples

20 x SSC 175.3 g NaCl

88.2 g sodium citrate ad 1000 ml with ddH ₂ 0 pH 7.0 with 10 N NaOH

10 x MEN 200 mM MOPS

50mM sodium acetate .10mM EDTA pH 7.0

NSEB buffer 0.25 M sodium phosphate buffer pH 7.2

7% SDS

1mM EDTA "" *

1% BSA (w / v) 4 x Laemmli buffer

200 mM Tris pH 6.8 8% SDS

0.4% bromophenol blue 40% glycerin

Methods used in the examples:

1. Cloning procedure

The vector pUClδ was used for cloning in E. coli. For the plant transformation, the gene constructions were cloned into the binary vector pBinAR (Höfgen and Willmitzer, Plant Sei. 66 (1990), 221-230).

2. Bacterial strains

E.coli strain DH5α (Bethesda Research Laboratories, Gaithersburgh, USA) was used for the pUC vectors and for the pBinAR constructs.

The transformation of the plasmids into the tobacco plants was carried out using the Agrobacterium tumefaciens strain C58C1 pGV2260 (Deblaere et al., Nucl. Acids Res. 13 (1985), 4777-4788).

3. Transformation of Agrobacterium tumefaciens

The DNA was transferred by direct transformation according to the method of Höfgen & Willmitzer (Nucleic Acids Res. 16 (1988), 9877). The plasmid DNA of transformed agrobacteria was isolated according to the method of Birnboim & Doly (Nucleic Acids Res. 7 (1979), 1513-1523) and analyzed by gel electrophoresis after suitable restriction cleavage. 4. Transformation of tobacco

An overnight culture of the corresponding Agrobacterium turne faciens clone was centrifuged off (6500 rpm; 3 min) and the bacteria were resuspended in YEB medium. Tobacco leaves from a tobacco sterile culture (Nicotiana tabacum cv. Samsun NN) were cut into small pieces of approximately 1 cm ^{2 in} size and bathed in the bacterial suspension. The leaf pieces were then placed on MS medium (0.7% agar) and incubated for 2 days in the dark. Then the leaf pieces for shoot induction on MS medium (0.7% agar) with 1.6% glucose, 1 mg / 1 6-benzylaminopurine, 0.2 mg / 1 naphthylacetic acid, 500 mg / 1 claforan and 50 mg / 1 kanamycin. The medium was changed every 7 to 10 days. When sprouts developed, the leaf pieces were transferred to glass jars containing the same medium. Resulting shoots were cut off and placed on MS medium + 2% sucrose + 250 mg / 1 claforan and whole plants were regenerated from them.

5. Radioactive labeling of DNA fragments

The radiocative labeling of DNA fragments was carried out using a DNA random primer labeling kit from Boehringer (Germany) according to the manufacturer's instructions.

6. Northern blot analysis

RNA was isolated from leaf tissue from plants according to standard protocols. 50 μg of the RNA were separated on an agarose gel (1.5% agarose, 1 x MEN buffer, 16.6% formaldehyde). After the gel run, the gel was briefly washed in water. The RNA was transferred to a Hybond N nylon membrane (Amersham UK) with 20 × SSC using capillary blot. The membrane was then baked at 80 ° C under vacuum for two hours. The membrane was prehybriized in NSEB buffer for 2 h at 68 ° C. and then hybridized in NSEB buffer overnight at 68 ° C. in the presence of the radioactively labeled sample.

7. Isolation of proteins from leaf tissue and Western blot analysis

To isolate proteins from leaf tissue, 2 circular leaf pieces with a diameter of approx. 5 mm were punched out of tobacco leaves and crushed in 100 μl 4x Laemmli buffer, 5% ß-mercaptoethanol in an Eppendorf reaction vessel. The resulting suspension was briefly centrifuged off. 10 μl of the supernatant were applied directly to a “MighTy Small” SDS polyacrylamide gel from Höfer (separating gel 10% polyacrylamide; collecting gel 3.5% polyacrylamide) and separated by gel electrophoresis. The proteins were then transferred to a nitrocellulose membrane using the Semidry electroblot method. The sucrose transporter from spinach in the extracts of transgenic tobacco plants was identified using a "blotting detection kit for rabbit antibodies" (Amersham UK) according to the manufacturer's instructions. The monoclonal antibody from mouse 9E10 (Kolodziej and Young, In: Methods in Enzy ology 194 (1991), 508-519), which is directed against the myc epitope shown as fragment D in FIG. 1, was used as the primary antibody .

8. Plant husbandry

In the greenhouse: light period 14 h at 1300 lux and 25 ° C

Dark period 10 h at 20 ° C

Humidity 60% In the phytotron: light period 15 h at 800 m Einstein / m ² / sec at 25 ° C dark period 9 h at 22 ° C

Humidity 80%

The examples illustrate the invention.

example 1

Construction of the plasmid pΩ-S21 and introduction of the plasmid into the genome of tobacco plants

To construct a plasmid which is suitable for the transformation of plant cells and leads to the overexpression of a sucrose transporter in plant cells, the coding region of a cDNA which encodes a sucrose transporter from spinach was first isolated. The clone pS21 (described in Riesmeier et al., EMBO J. 11 (1992), 4705-4713) was used for this. Using the oligonucleotides

(1) 5 '-GAGACTGCAGCCATGGCAGGAAGAAATATATAAAAAATGGTG-3'

(Seq ID No. 1) and

(2) 5 ^• -GAGACTGCAGTCAGTTGAGGTCTTCTTCGGAGATTAGTTTTTGTTC

ATGACCACCCATGGACCCACCAATTTTAGC-3 '(Seq ID No. 2)

With the help of PCR technology an approximately 1600 bp long DNA fragment was amplified, which contained nucleotides 70 to 1644 of the Riesmeier et al. (EMBO J. 11 (1992), 4705-4713) comprises the sequence of the clone pS21. The oligonucleotide (1) introduced a Pst I and a Noc I interface at the 5 'end of the coding region. The coding region was extended by the oligonucleotide (2) by an 11 amino acid long sequence (EQKLISEEDLN-COOH (Seq ID No. 3)) at the C-terminus and a Pst I site was also introduced. This sequence originates from the c-Myc gene and represents the recognition epitope for the monoclonal antibody from mouse 9E10 (Kolodziej and Young, In: Methods in Enzymology 194 (1991), 508-519; commercially available from Dianova, Hamburg).

The resulting PCR product was cut with the restriction enduclease Pst I and ligated into a pUClδ vector cut with Pst I. The resulting plasmid was named p-S21-Myc8. An approximately 1600 bp fragment containing the PCR product was isolated from this by Nco I / Pst I partial digestion and ligated into the vector p35SDE-Ω-OCS cut with Nco I and Pst I. The vector p35SDE-Ω-OCS was produced as follows: A 530 bp EcoR I / Asp718 fragment (nucleotides 6909-7439 (Franck et al. Cell 21 (1980), 285-294) was generated from the promoter region of the Cauliflower Mosaic Virus. isolated and ligated into a pUC18 vector cut with EcoR I and Asp718. The resulting plasmid was called p35S. An approximately 330 bp fragment was then isolated from the EcoR I / Asp718 promoter fragment by restriction digestion with the endonucleases Hinc II and EcoR V. This fragment was then cloned into the filled-in Nco I interface of the 35S promoter in the plasmid p35S. In this case, a construct was created in which two Hinc II / EcoR V fragments were inserted one behind the other in reverse orientation in the Nco I interface, the arrangement being as follows:

EcoRI (NcoI) / (EcoRV) --- 330bp (HincII) / (EcoRV) ---

330bp (HincII) / (Ncol) 525 bp Asp718

The resulting plasmid was named p35SDE. The 35S promoter contained in this fragment with two additional Hinc II / EcoR V fragments was designated 35SDE. Another pUC plasmid was constructed, which is constructed as shown in FIG. 3. The following DNA fragments were inserted between the EcoR I and the Hind HI sites of the polylinker of a pUC18 vector:

1. EcoR I / Asp718 fragment of the 35S promoter (nucleotides 6909-7439 (Franck et al., Cell 21 (1980), 285-294))

2. Asp718 / Nco I fragment (TMV-Ul) from the Ω translation enhancer of the tobacco mosaic virus with the following sequence: 5 '-GGTACCTTTACAACAATTACCAACAACAACAAACAACAAACAACAT TACAATTACTATTTACAATTACCATGG-3' (Seq ID No. 4)

3. a polylinker with the following restriction sites Nco I / Sac I / Xho I / Sma I / BamH I / Xba I / Sal I / Pst I / Sph I

4. a termination sequence from the octopine synthase gene (nt 11748-11939 of the T-DNA of the Ti plasmid pTiACH5 (Gielen et al., EMBO J. 3 (1984), 835-846)

This plasmid was called p35S-Ω-OCS.

The plasmid p35S-Ω-OCS was cut with EcoR I / Asp718, whereby the 35S promoter was removed. This was replaced by the promoter 35SDE isolated with EcoR I and Asp718 from the plasmid p35SDE. The resulting plasmid was named p35SDE-Ω-OCS.

This plasmid was cut with Nco I and Pst I in the polylinker. The approximately 1600 bp fragment which contains the PCR product described above and was isolated from the plasmid p-S21-Myc8 by partial digestion with Nco I and Pst I was ligated into the interfaces. This resulted in the plasmid pΩA7DE-S21-Myc8. This plasmid is shown in Figure 1.

Plasmid pΩA7DE-S21-Myc8 was digested with EcoR I and Hind III and the entire expression cassette comprising the promoter 35SDE, the translation enhancer, the region coding for the saccharose transporter from spinach, with the sequence containing the c-Myc epitope coded, and the termination sequence isolated.

This sequence was ligated into the vector TCSAS cut with EcoR I and Hind III (deposited with the German Collection of Microorganisms in Braunschweig, Germany, on August 10, 1994 under the accession number DSM 9359), from which the EcoR I / Hind III digestion, the expression cassette contained between these two restriction sites was removed. The resulting plasmid was called pΩ-S21 and is shown in Figure 2.

Example 2 Transformation of tobacco plants with the plasmid pΩ-S21

The plasmid pΩ-S21 was used for the transformation of tobacco plants with the aid of the agrobacterium-mediated gene transfer.

As a result of the transformation, the transcript coding for the sucrose transporter from spinach could be detected in different amounts in transgenic tobacco plants. The detection was carried out using a Northern blot analysis. For this, RNA was isolated from leaf tissue of transgenic and non-transformed plants. 50 μg of this RNA were separated on an agarose gel, transferred to a nylon membrane and hybridized with the radioactively labeled cDNA, which encodes the sucrose transporter from spinach. Such a Northern blot analysis showed that out of three transformants (transformants No. 5, 12 and 32) two transformants (No. 12 and No. 32) have a high expression of the sucrose transporter from spinach, one In comparison, transformants (No. 5) showed only a relatively low expression of the sucrose transporter from spinach, and no transcripts could be found in non-transformed potato plants which encoded the sucrose transporter from spinach.

In order to show that the transcript coding for a sucrose transporter from spinach leads to the synthesis of a sucrose transporter in transgenic tobacco plants, a Western blot analysis was carried out. For this purpose, proteins were isolated from leaf tissue of transgenic plants, separated on an SDS gel and transferred to a nitrocellulose membrane. The detection of the spinach-sucrose transporter in transgenic tobacco plants was carried out with the help of monoclonal Antibodies directed against the epitope of the c-Myc gene encoded by the 3 'end of the coding region in the plasmid pΩ-S21.

In Western blot analyzes of this type, an approximately 48 kD protein was specifically detected in protein extracts from transgenic tobacco plants. This corresponds to the expected molecular weight of the sucrose transporter from spinach.

As a result of the expression of the sucrose transporter from spinach, the tobacco plants transformed with the plasmid pΩ-S21 had a different flowering behavior compared to non-transformed tobacco plants. In particular, in the case of transformants 12 and 32, which showed a strong expression of the spinach-sucrose transporter, premature flower formation and a slightly increased flower set were observed.

In comparison to non-transformed plants, transformed tobacco plants showed significantly fewer leaf attachments before the induction of the apical meristem started to form the inflorescences. Table I shows how many leaf batches, approximately 128-day-old transformed or non-transformed tobacco plants which were kept in the phytotron, had on average before the apical meristem was differentiated into inflorescences.

Table I

transformed average number of tobacco line No. of leaf roots

5 17.8 12 18 32 17.3

non-transformed 20.7 plants The premature induction of the meristem for the formation of inflorescences leads to the premature formation of buds and the premature flowering in comparison to wild-type plants. This is also illustrated in FIGS. 4a and b, which show transformed tobacco plants of line 12 (FIG. 4a) and line 32 (FIG. 4b) kept in the phytron in comparison to non-transformed tobacco plants. Under the same cultivation conditions, the flowering and flowering of untransformed tobacco plants started significantly later, on average approx. 14 days for plants kept in the phytotron.

In addition to the premature flower formation, the transformed plants have more flowers in comparison to wild-type plants. This is shown in Table II.

Table II

transformed average number of tobacco line number of flowers per plant

5 112 12 170 32 133

untransformed 103 plants

The plants examined were approximately 128 days old and had been kept in the phytotron.

The results described above were confirmed in a repeat experiment in which plants of the transformed lines 32, 12, 5 and 1 were examined. The results are shown in FIGS. 5, 6 and 7. SEQUENCE LOG

(1. GENERAL INFORMATION:

(i) APPLICANT:

(A) NAME: Institute for Genetic Research Berlin

GmbH

(B) ROAD: Ihnestr. 63

(C) LOCATION: Berlin

(E) COUNTRY: Germany

(F) POSTAL NUMBER: 14195

(G) TELEPHONE: +49 30 8300070 (H) TELEFAX: +49 30 83000736

(ii) DESCRIPTION OF THE INVENTION: Process for changing the flowering behavior in plants

(iii) NUMBER OF SEQUENCES: 4

(iv) COMPUTER READABLE VERSION:

(A) DISK: Floppy disk

(B) COMPUTER: IBM PC compatible

(C) OPERATING SYSTEM: PC-DOS / MS-DOS

(D) SOFTWARE: Patentin Release # 1.0, Version # 1.30 (EPA)

(v) DATE OF REGISTRATION: APPLICATION NUMBER: DE P4439748.8

(2) INFORMATION ON SEQ ID NO: 1:

(i) SEQUENCE LABEL:

(A) LENGTH: 42 base pairs

(B) TYPE: nucleotide

(C) STRAND FORM: Single strand

(D) TOPOLOGY: linear

(ii) MOLECULE TYPE: Other nucleic acid

(AI DESCRIPTION: / desc = "oligonucleotides"

(iii) HYPOTHETICAL: YES

(iv) ANTISENSE: NO

(xi) SEQUENCE DESCRIPTION: SEQ ID NO: 1:

GAGACTGCAG CCATGGCAGG AAGAAATATA TAAAAAATGG TG 42 (2) INFORMATION ON SEQ ID NO: 2:

(i) SEQUENCE LABEL:

(A) LENGTH: 76 base pairs

(B) TYPE: nucleotide

(C) STRAND FORM: Single strand

(D) TOPOLOGY: linear

(ii) MOLECULE TYPE: Other nucleic acid

(A) DESCRIPTION: / desc = "oligonucleotides"

(iii) HYPOTHETICAL: YES

(iv) ANTISENSE: NO

(xi) SEQUENCE DESCRIPTION: SEQ ID NO: 2:

GAGACTGCAG TCAGTTGAGG TCTTCTTCGG AGATTAGTTT TTGTTCATGA CCACCCATGG 60

ACCCACCAAT TTTAGC 76

(2) INFORMATION ON SEQ ID NO: 3:

(i) SEQUENCE LABEL:

(A) LENGTH: 11 amino acids

(B) TYPE: amino acid

(C) STRAND FORM: Single strand

(D) TOPOLOGY: linear

(ii) MOLECULE TYPE: Peptide (iii) HYPOTHETICAL: YES (iv) ANTISENSE: NO

(xi) SEQUENCE DESCRIPTION: SEQ ID NO: 3:

Glu Gin Lys Leu Ile Ser Glu Glu Asp Leu Asn 1 5 10 (2) INFORMATION ON SEQ ID NO: 4:

(i) SEQUENCE LABEL:

(A) LENGTH: 73 base pairs

(B) TYPE: nucleotide

(C) STRAND FORM: Single strand

(D) TOPOLOGY: linear

(ii) MOLECULE TYPE: Other nucleic acid

(A) DESCRIPTION: / desc = "oligonucleotides"

(iii) HYPOTHETICAL: YES

(iv) ANTISENSE: NO

(xi) SEQUENCE DESCRIPTION: SEQ ID NO: 4:

GGTACCTTTA CAACAATTAC CAACAACAAC AAACAACAAA CAACATTACA ATTACTATTT 60

ACAATTACCA TGG 73

Claims

Patent claims

1. Use of DNA molecules which encode proteins with the biological activity of a sucrose transporter to change the flowering behavior in plants.

2. Use according to claim 1, wherein the change in the flowering behavior is based on an increase in the activity of the sucrose transporter.

3. Use according to claim 2, wherein the flowering behavior is changed so that there is premature flowering and flowering.

4. Use according to claim 2 or 3, wherein the Blühverhal¬ th is changed so that an increased flowering takes place.

5. Use according to one of claims 2 to 4, wherein the increase in the activity of the sucrose transport takes place by introducing and expressing DNA molecules in plants which encode a sucrose transporter.

6. Use according to any one of claims 1 to 5, wherein the DNA molecule encodes a vegetable sucrose transporter.

7. Use according to any one of claims 1 to 5, wherein the DNA molecule encodes a sucrose transporter from a fungus.

8. Use according to one of claims 1 to 5, wherein the DNA molecule encodes a bacterial sucrose transporter.

9. A method for changing the flowering behavior in plants, characterized in that the activity of the sucrose transporter is increased in plants.

10. The method according to claim 9, wherein the increase in sucrose transporter activity is achieved by introducing and expressing DNA molecules in plants which encode a sucrose transporter.

11. The method of claim 10, wherein the DNA molecule encodes a plant sucrose transporter.

12. The method of claim 10, wherein the DNA molecule encodes a sucrose transporter from a fungus.

13. The method of claim 10, wherein the DNA molecule encodes a bacterial sucrose transporter.

14. Transgenic plant with a different flowering behavior compared to the wild type plant, characterized in that the plant has an increased sucrose transporter activity compared to the wild type plant.

15. Transgenic plant according to claim 14, in which the flowering behavior is changed in such a way that there is premature flowering and flowering in comparison with the wild-type plant.

16. The transgenic plant according to claim 14 or 15, in which the flowering behavior is changed such that there is an increased flower set compared to the wild-type plant.

17. Transgenic plant according to one of claims 14 to 16, wherein the increase in sucrose transporter activity by introducing and expressing DNA molecules which encode a sucrose transporter.

18. The transgenic plant according to claim 17, wherein the DNA molecule encodes a plant sucrose transporter.

19. Transgenic plant according to claim 17, wherein the DNA molecule encodes a sucrose transporter from a fungus.

20. The transgenic plant according to claim 17, wherein the DNA molecule encodes a bacterial sucrose transporter.