WO2016120657A1

WO2016120657A1 - Polynucleotide associated with ergosterol biosynthesis and uses thereof

Info

Publication number: WO2016120657A1
Application number: PCT/IB2015/000258
Authority: WO
Inventors: Asis Datta; Niranjan Chakraborty; Subhra Chakraborty; Mohan KAMTHAN; Ayushi Kamthan
Original assignee: National Institute Of Plant Genome Research
Priority date: 2014-12-25
Filing date: 2015-03-02
Publication date: 2016-08-04

Abstract

The present disclosure provides a polynucleotide encoding an ergosterol biosynthesis enzyme, ∆7-sterol-C-5-desaturase from tomato. The present disclosure also provides recombinant DNA constructs, recombinant vectors and recombinant host cells comprising the polynucleotide coding for a polynucleotide having C-5 sterol desaturase activity. The present disclosure further provides a method for obtaining a transgenic plant that expresses a polypeptide with C-5 sterol desaturase activity that confers enhanced drought tolerance, pathogen resistance, and nutritional quality to the transgenic plant.

Description

POLYNUCLEOTIDE ASSOCI ATED W ITH ERGOS TERO L

BIOSYNTHESIS AND USES THEREO F

FIELD OF THE INVENTION

[0001 ] The present disclosure provides a polynuc leotide encod ing an ergosterol biosynthesis enzyme, A7-sterol-C-5-desaturase from tomato. The present disclosure also provides recombinant DNA constructs, recombinant vectors and recombinant host cells comprising the polynucleotide coding for a polynucleotide having C-5 sterol desaturase activity. The present disclosure further provides a method for obtaining a transgenic plant that expresses a polypeptide with C-5 sterol desaturase activity that confers enhanced drought tolerance, pathogen resistance, and nutritional quality to the transgenic plant.

BACKGROUND OF THE INVENTION

[0002] Development of the transgenic crops with multiple beneficial traits has emerged as an important area in the field of plant biotechnology. Crop genetic engineering aims at improving environmental stress (biotic and abiotic) tolerance as well as nutritional quality. Empowering a single crop with multiple traits is high ly demanding and requires manipulation of more than one gene.

[0003] Among all the environmental factors limiting crop yield, drought probably is the abiotic stress with the highest impact. Besides, biotic stress imposed on crops by plant pathogens are a real threat to worldwide agriculture. Phytopathogens like Sclerotinia sclerotiorum cause substantial loss in crop yield each year throughout the world. This fungus has a broad host range resulting in about 95% loss of economically important crops like rapeseed, bean, tomato, and sunflower. Thus, transgenic strategies that lead to improved tolerance to drought, and phytopathogens can significantly contribute to improvement in crop yield.

[0004] Plants are the ultimate source of nutrients in human diet. However, all our major food crops lack certain essential nutrients. Malnutrition is a significant public health issue in most of the developing countries where majority of population relies on staple crops, such as rice or wheat, which does not provide the ful l complement of essential nutrients. For example, iron deficiency is the most widespread microiuitrient deficiency, affecting about 2 billion people. Also the essential co-3 and c -6 polyunsaturated fatty acids (PUFAs) which are known to have diverse roles in metabolism, cardiovascular health, inflammatory responses, blood pressure regulation, etc. cannot be synthesized de-novo and must be supplied in the diet. Thus, it is conceivable that one of the major goals of genetic engineering is to improve essential nutrient content in the staple crops. This includes enhancing the level of bio-available iron, and PUFAs.

[0005] The epicuticular waxes which form the outermost layer of aerial plant organs are considered to confer resistance to insect herbivores, fungal pathogens, and drought (Eigenbrode et al., Annu. Rev. Entomol., 1995.40, 117-142; Jenks, Plant Physiol., 1994, 105.1239-1245; Jordan, Crop Sci., 1984,24, 1168-1173).

[0006] The cuticular waxes are complex mixtures of primarily very long chain fatty acids (VLC, > CI 8), hydrocarbons, alcohols, aldehydes, ketones, triterpenes, sterols and flavonoids. Modification of cuticular wax layer is one of the strategies to improve drought tolerance by reducing transpirational water loss. A feature common to some of the enzymes involved in epicuticular wax biosynthesis including OsGI - 2 from rice (Islam, Plant Mol. Biol., 2009, 70, 443-456), CER1 and WAX2 from Arabidopsis (Aarts et al., Plant Cell, 1995, 7, 2115-2127; Chen et al., Plant Cell. 2003, 15, 1170-1185), TaCerJ from wheat (Hu et al., Acta. Physiol. Plant, 2009, 31, 1111-1118), and GLJ from maize (Sturaro et al., Plant Physiol., 2005, 138, 478- 489) is the presence of N-terminal region exhibiting homology to the C-5 sterol desaturase (FA hydroxylase superfamily) besides an uncharacterized wax-C superfamily domain. FA hydroxylase superfamily consists of a large family of integral membrane enzymes such as fatty acyl desaturases, hydroxylases, ketolases, decarbonylases and monooxygenases found in prokaryotes and eukaryotes characterized by the conserved histidine rich motifs that form di-iron-binding site essential for catalytic activity. C-5 sterol desaturase (ERG3) is a membrane bound enzyme that catalyzes the introduction of a C-5 double bond into the B ring of Δ7- sterols to produce the corresponding Δ5, 7-sterols. It has been cloned and characterized in many organisms including Saccharo yces cerevisiae, Arabidopsis thalian , Homo sapiens, Candida albicans and most recent ly i n alga C711 a my do monas reinliardlii.

[0007] PCT/US2002/200255 describes a method o f deve loping transgen ic plants with altered leve ls of steroid compou nds.

SUMMARY OF THE INVENTION

[0008] Th is summary is provided to introduce concepts related to polynucleotide encod ing an ergostero l biosynthesis enzyme. Th is summary is not intended to identify essential features of the claimed subject matter not is it intended for use in determining or limiting the scope of the claimed subject matter.

[0009] In an aspect of the present disclosure, there is provided a cDNA fragment encoding a polypeptide having amino acid sequence as set forth in SEQ ID NO: 2.

[0010] In an aspect of the present disclosure, there is provided a recombinant DNA construct comprising a transcribeable polynucleotide fragment encod ing a polypeptide having am ino acid sequence as set forth in SEQ I D NO: 2, said transcribeable polynucleotide fragment operably l inked to a promoter.

[0011 ] In an aspect of the present disclosure, there is provided a recombinant DNA vector comprising the recombinant DNA construct comprising a transcribeable polynucleotide fragment encod ing a polypeptide having amino acid sequence as set forth in SEQ ID NO: 2, said transcribeable polynucleotide fragment operably linked to a promoter.

[0012] In an aspect of the present d isclosure, there is provided a recombinant host cell comprising the recombinant DNA vector comprising the recombinant DNA construct comprising a transcribeable polynucleotide fragment encoding a polypeptide having am ino acid sequence as set forth in SEQ ID NO: 2, said transcribeable polynucleotide fragment operably linked to a promoter.

[0013] In an aspect of the present d isclosure, there is provided a recombinant host cell encod ing a transcribeable polynucleotide fragment encoding a polypeptide having am ino acid sequence as set forth in SEQ ID NO: 2, wherein said transcribeable polynucleotide fragment has polynucleotide sequence as set forth in SEQ I D NO: 1 , and where i n said polypeptide has C-5 stero l desaturase enzyme act ivi ty.

[0014 ] I n an aspect of the present d isclosure, there is prov ided a method of producing a transgen ic plant, said method com prising: (a) transform i ng a plant cel l with a polynuc leotide fragment comprising a cDNA fragment encod ing a polypeptide having an am ino ac id sequence as set forth i n SEQ I D NO: 2 ; (b) se lecting a transgen ic plant cel l expressing a polypeptide encoded by said cDNA fragment; and (c) developing a transgen ic plant, wherein said transgen ic plant has enhanced physiological characteristics selected from the group consisting of drought tolerance, pathogen resistance, and nutritional quality.

[0015] In an aspect of the present disclosure, there is provided a transgen ic plant or parts thereof including seeds prepared by a method of produc ing a transgenic plant, said method comprising: (a) transform ing a plant cell with a polynucleotide fragment comprising a cDNA fragment encoding a polypeptide having an amino acid sequence as set forth in SEQ ID NO: 2; (b) selecting a transgenic plant cel l expressing a polypeptide encoded by said cDNA fragment; and (c) developing a transgenic plant, wherein said transgenic plant has enhanced physiological characteristics selected from the group consisting of drought tolerance, pathogen resistance, and nutritional quality.

[0016] In an aspect of the present disclosure, there is provided a transgen ic plant or parts thereof including seeds comprising a genome encoded polynucleotide sequence encod ing a polypeptide having amino acid sequence as set forth in SEQ ID NO: 2, wherein said genome encoded polynucleotide sequence has polynucleotide sequence as set forth in SEQ ID NO: 1 .

[0017] These and other features, aspects, and advantages of the present subject matter will be better understood with reference to the fol lowing description and appended claims. This summary is provided to introduce a selection of concepts in a simplified form. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to lim it the scope of the claimed subject matter. BRIEF DESC RIPTION OF ACCOMPANYING DRAWINGS

[0018] Figure 1 depicts stages of rice transformation; Figure 1 (A) depicts callusing; Figure 1 (B) depicts agroin fection; Figure 1 (C) depicts selection; Figure 1 (D) depicts regeneration 1 ; Figure I (E) depicts regeneration 2; and Figure 1 (F) depicts transformed rice plants transferred to pots; in accordance with an embodiment of the present disclosure.

[0019] Figure 2 depicts sequence al ignment between C-5 sterol desaturase from tomato (LeC5SD) and Flammuliiui vel tipes (FvCSSD), in accordance with an embodiment of the present disclosure.

[0020] Figure 3(A) depicts that LeC5SD consists of larger size introns (603& 848bp); and Figure 3(B) depicts that ¥vC5SD has smaller introns of (44bp and 53bp), in accordance with an embodiment of the present disclosure.

[0021] Figure 4 depicts phenotypic complementation of dwf7 mutant of Arabidopsis; Figure 4(A) depicts phenotypic difference in stems in dwf7 mutant and Lec5SD complemented plant; Figure 4(B) depicts phenotypic difference in roots in dwf7 mutant and Lec5SD complemented plant; Figure 4(C) depicts phenotypic difference in si lique in dwf7 mutant and Lec5SD complemented plant; Figure 4(D) depicts phenotypic difference in leaves in dwf7 mutant and Lec5SD complemented plant; Figure 4(E) depicts a graphical representation of comparison of plant length in dwf7 mutant and Lec5SD complemented plant; Figure 4(F) sub-cellular localization of LeC5SD in onion epidermal peel with LeC5SD-G¥P construct; Figure 4(G) depicts an image of phase contrast microscopy for sub-cellular localization of LeC5SD in onion epidermal peel with LeC5SD-GFP construct; in accordance with an embodiment of the present disclosure.

[0022] Figure 5(A) depicts a schematic showing RNAi strategy; Figure 5(B) depicts a binary vector pB 1 121 used for plant transformation; Figure 5(C) depicts PCR analysis to confirm transgene integration; and Figure 5(D) depicts northern analysis for expression of LeC5SD gene (WT: wild type; Ox: over-expression lines); in accordance with an embodiment of the present disclosure. [0023 ] Figure 6 depicts pathogenesis assay of transgenic plants with Scelrotinia sc/erotiorum; [Figure 6(A)] on the day of inoculation; and [Figure 6(B)] on the fifth day post-inoculation; in accordance with an embodiment of the present disclosure.

[0024) Figure 7 depicts trypan blue staining of fungal mycelia; [Figure 7(A)] in the uninfected leaf; [Figure 7(B)] in the infected leaf; and [Figure 7(C)] in the fungal mycelial disc; in accordance with an embodiment of the present disclosure.

[0025] Figure 8 depicts drought tolerance assay; [Figure 8(A)] in the RNAi lines; [Figure 8(B)] in the overexpression lines; in accordance with an embodiment of the present disclosure.

[0026] Figure 9(A) depicts expression level of endogenous LeC5SDmRNA in drought induced stress as determined by qRT-PCR; Figure 9(B)/C) depicts wax content of leaf cuticular waxes of wild type and transgenic lines as determined by GC-MS; Figure 9(D) depicts total iron content as determined by atomic absorption spectrometry; and Figure 9(E) depicts quantitation of polyunsaturated fatty acid in wild type and transgenic lines as determined by GC-MS; in accordance with an embodiment of the present disclosure.

[0027] Figure 10 depicts sequence alignment between C-5 sterol desaturase homolog from rice (Os01g04260) and tomato (LeC5SD), in accordance with an embodiment of the present disclosure.

[0028] Figure 11(A) depicts scanning electron microscopy images of Pusa Basmati leaves showing epicuticular wax distribution; and Figure 11(B)/(C) depict quantization of epicuticular wax from rice leaves by GC-MS, in accordance with an embodiment of the present disclosure.

[0029] Figure 12(A) depicts sequence alignment between Arabidopsis Delta-7 C-5 sterol desaturase and C-5 sterol desaturase from tomato (Lec5SD); and Figure 12(B) depicts sequence alignment between Arabidopsis Delta-7 C-5 sterol desaturase and C-5 sterol desaturase from fungus. (FvC5SD).

[0030] Figure 13(A) depicts silique, root and leaf length in dwf7 mutant; Figure 13(B) depicts silique, root and leaf length in FvC5SD complemented plant; and Figure 13(C) depicts silique, root and leaf length in LeC5SD complemented plant. DETAILED DESCRIPTION OF INVENTION

[0031] Those skilled in the art will be aware that the disclosure described herein is subject to variations and modifications other than those specifically described. It is to be understood that the disclosure described herein includes all such variations and modifications. The disclosure also includes all such steps, features, compositions and compounds referred to or indicated in this specification, individually or collectively, and any and all combinations of any or more of the steps or features. Definitions

[0032] For convenience, before further description of the present disclosure, certain terms employed in the specification and examples are collected here. These definitions should be read in light of the remainder of the disclosure and understood as by a person of skill in the art. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by a person of ordinary skill in the art.

[0033] The articles "a", "an" and "the" are used to refer to one or to more than one

(i.e., to at least one) of the grammatical object of the article.

[0034] The term "plurality" means more than one.

[0035] The terms "at least two," "more than one" and "plurality" are used interchangeably.

[0036] Throughout this specification, unless the context requires otherwise the word "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated element or step or group of element or steps but not the exclusion of any other element or step or group of element or steps.

[0037] The term "including" is used to mean "including but not limited to". "Including" and "including but not limited to" are used interchangeably.

[0038] The term "amino acid sequence" means the sequence of amino acids that characterizes a given protein.

[0039] The term "polypeptide" means a polymer of amino acids joined together by peptide bonds.

[0040] The term "polynucleotide" used in the present disclosure refers to a DNA polymer composed of multiple nucleotides chemically bonded by a series of ester linkages between the phosphor) I group of one nucleotide and the hydroxyl group of the sugar in the adjacent nucleotide.

[0041 ] The polynucleotides described in the present description include "genes" and nucleic acid molecules described including "vectors" or '^'plasmids". Accordingly, the term "gene^", also called a "structural gene" refers to a polynucleotide that codes for a particular sequence of amino acids, which comprise all or part of one or more proteins or enzymes, and may include regulatory (non-transcribed) DNA sequences, such as promoter sequences, which determine for example the conditions under which the gene is expressed.

[0042] The term "nucleotide sequence" means the order in which nucleotides are situated in a chain relative to one another.

[0043] The term "sequence identity" means the number percentage of matches in positions from an alignment of two molecular sequences.

[0044] The term "primer" refers to a single-stranded oligonucleotide, the 3' end of which can be used as the initiation site for the DNA synthesis with a DNA polymerase.

[0045] A "vector" is any means by which a nucleic acid can be propagated and/or transferred between organisms, cells or cellular components. Vectors include viruses, bacteriophage, pro-viruses, plasmids, phagemids, transposons and artificial chromosomes such as YACs (yeast artificial chromosomes), BACs (bacterial artificial chromosomes), and PLACs (plant artificial chromosomes), and the like, that are "episomes", that is, that replicate autonomously or can integrate into a chromosome of a host cell. A vector can also be a naked RNA polynucleotide, a polynucleotide composed of both DNA and RNA within the same strand, a poly- lysine-conjugated DNA or RNA, a peptide conjugated DNA or RNA, a liposome- conjugated DNA, or the like, that are not episomal in nature, or it can be an organism which comprises one or more of the above polynucleotide constructs such as Agrobacterium or a bacterium.

[0046] The term "recombinant" means a cell or organism in which genetic recombination has occurred. It also includes a molecule (e.g., a nucleic acid or a polypeptide) that has been artificially or synthetically (i.e., non-naturally) altered by human intervention. The alteration can be performed on the molecule within, or removed from, its natural environment or state.

[0047] The term "recombinant vector" means a vector carrying a foreign DNA fragment.

[0048] The term "recombinant host cell^" means a host cell carrying a recombinant vector.

[0049] The term "recombinant DNA construct" means a molecule that is constructed outside living cells by joining natural or synthetic DNA to a DNA molecule that can replicate in a living cell.

[0050] The term "promoter" refers to a polynucleotide molecule that is in its native or non native state located upstream or 5' to a translational start codon of an open reading frame (or protein-coding region) and that is involved in recognition and binding of RNA polymerase II and other proteins (trans-acting transcription factors) to initiate transcription.

[0051] The term "transformation" refers to the process by which a recombinant DNA molecule is introduced into a host cell. Transformation (or transduction, or transfection), can be achieved by any one of a number of means including electroporation, microinjection, biolistics (or particle bombardment-mediated delivery), or Agrobacterium- mediated transformation.

[0052] The term "transgenic plant" means plant that has been genetically engineered to artificially introduce a gene or set of gene sequences in the plant genome.

[0053] A transgenic "plant cell" means a plant cell that is transformed with stably- integrated, non-natural, recombinant polynucleotides, e.g. by Agrobacterium- mediated transformation or by bombardment using micro particles coated with recombinant polynucleotides.

[0054] The term "expression" with respect to a gene sequence refers to transcription of the gene and, as appropriate, translation of the resulting mRNA transcript to a protein. Thus, as will be clear from the context, expression of a protein results from transcription and translation of the open reading frame sequence.

[0055] The term "ergosterol" means a white crystalline organic solid of the molecular formula C28H4 O belonging to the steroid family. Itjs a sterol of high industrial and commercial importance, since it can be readily converted to many therapeutically useful substances, such as ergocalciferol (vitamin D2) and several adrenal cortical and sex hormones. Ergosterol occurs naturally in yeasts, moulds fungi, and a variety of vegetable sources.

Description of sequences

(00561 SEQ ID NO: 1 depicts the nucleotide sequence of cD A fragment encoding A7-sterol-C-5-desaturase activity from tomato.

ATGGACGACTACTTGAATTTATTTGTAGAGGAGACGTCGlT^'mTAATAG GATTGTTCTGGGCACA^rrTCTTGCCGGAATCATGGTGGGGACCACTCCCTC ATTGGTTTC A AGGATGGCTTCGCAACTAC ATCGGTGG AGTCTTGCTCTAC TTTATCTCTGGGTTTCTTTGGTGCTTCTACATCTACTACTTAAAACGCAAT GTTTATCTACCTAAAGATGCCATCCCTTCAAATAGAGCTATGCTCTTGCA AATAGGAGTTGCAATGAAAGCTATGCCATGGTACTGTGCCCTTCCATCAC TTTCTGAGTACATGATTGAAAATGGGTGGACTAAATGT CTCAAGAATA AGCGATGTCGGATGG ATACCCTACCTTATCTATGTTGCAGTrTATCTGGT AATAGTAGAATTTGGTATCTATTGGATGCATCGAGAGTTGCATGACATA AAACCTCTGTACAAATATCTCCATGCTACACATCATATATACAACAAGCA AAATACACTCTCCCCATTTGCTGGTTTGGCATTCCACCCATTGGATGGAA TACTACAGGCAGTGCCACACGTAATAGCTCTTTTTCTGTTGCCTGTGCAT TTCACCACACACATTGCTCTCTTATTCATAGAAGCCATATGGACTGCAAA TATTCATGACTGTATACATGCGAAGGTrTGGCCTGTAATGGGTGCCGGTT ACCATACCATCCACCATACTACGTACCGCCATAATTATGGTCACTACACA ATATGGATGGACTGGATGITTGGAACTCTTCGCGATCCTGTTGAAGATGA AGTGAAGAAACTGTAA

[0057] SEQ ID NO: 2 depicts amino acid sequence of a polypeptide having Δ7- sterol-C-5-desaturase activity encoded by a cDNA fragment having nucleotide sequence as set forth in SEQ ID NO: 1.

MDDYLNLFVEETSFFNRIVLGTFLPESWWGPLPHWFQGWLRNYIGGVLLYF ISGFLWCFYIYYLKRNVYLP DAIPSNRA LLQIGVAMKAMPWYCALPSLS EY IENGWT CFSRISDVGW1PYLIYVAVYLVIVEFG1YWMHRELHDIKPLY YLHATHHIYN QNTLSPFAGLAFHPLDGILQAVPHV1ALFLLPVHFTTH1AL LFI EA I WTAN IHDC I HA KV W PV GAG Y HTI H HTTYRHNYG HYTI W DWM F GTLRDPVEDEV KL

[0058] SEQ ID NO: 3 depicts sequence of the forward primer used to clone LeCSSD in to pG EMT vector.

GCTCTAGAATGGACGACTACTTGAATTTATTTGTAG

[0059) SEQ ID NO: 4 depicts sequence of the reverse primer used to. clone L&C5SD in to pGEMT vector.

CAGAGCTCTTACAGTTTCTTCACTTCATCTTCAAC

[0060J SEQ ID NO: 5 depicts sequence of the forward primer used to clone LeC5SD for construct 1 in to pHANNIBAL vector.

CTCGAGCAAAGATGATAGACAAATGAGCCC

[0061 ] SEQ ID NO: 6 depicts sequence of the reverse primer used to clone LeC5SD for construct 1 in to pHANNIBAL vector.

GAATTCCTTGTTGTATATATGATGTGTAGCATGG

[0062] SEQ ID NO: 7 depicts sequence of the forward primer used to clone antisense fragment of LeC5SD for construct 1 in to pHANNIBAL vector.

TCTAGACAAAGATGATAGACAAATGAGCCC

[0063] SEQ ID NO: 8 depicts sequence of the reverse primer used to clone antisense fragment of LeC5SD for construct 1 in to pHANNIBAL vector.

GGATCCCTTGTTGTATATATGATGTGTAGCATGG

[0064] SEQ ID NO: 9 depicts sequence of the forward primer used to clone fragment of LeC5SD for construct 2 in to pHANNIBAL vector.

CTCGAGCAACAAGCAAAATACACTCTCCCC

[0065] SEQ ID NO: 10 depicts sequence of the reverse primer used to clone fragment of LeC5SD for construct 2 in to pHANNIBAL vector.

GAATTC GCATCAAGAGCATTTCACAGTA

[0066] SEQ ID NO: 1 1 depicts sequence of forward primer used to clone antisense fragment of LeC5SD for construct 2 in to pHANNIBAL vector.

TCTAGACAACAAGCAAAATACACTCTCCCC

[0067] SEQ ID NO: 12 depicts sequence of reverse primer used to clone antisense fragment of LeC5SD for construct 2 in to pHANN IBAL vector. GGATCCGCATCA AGAGCATTTCACAGTA

[0068] SEQ ID NO: 13 depicts sequence of forward primer used to clone LcC5SD gene into pB l l 2 l vector.

GCTCTAGAATGGACGACTACTTGAATTTATTTGTAG

[0069] SEQ ID NO: 14 depicts sequence of reverse primer used to clone LeC5SD gene into pB 1 12 1 vector.

CAGAGCTCTTACAGTTTCTTCACTTCATCTTCAAC

[0070] SEQ ID NO: 15 depicts sequence of hairpin structure generated by construct 1.

CTCG AGC AGCTAC ACAGCCAGATC AC AACA ATTA ACACTACTAGTTGTG ACAAGTCAACAAAGAAATCTAAAAAATTGTGTGCCCCACTAACCTCTTT GTTACTTTCTCCAAATCTCTCTCTTCTCCGATCATCTCCCATCGGAATCT ACTGAATCGTCGATGGACGACTACTTGAATTTATTTGTAGAGGAGACGT CGTTTTTTAATAGGATTGTTCTGGGCACATTCTTGCCGGAATCATGGTG GGGACCACTCCCTCATTGGTTTCAAGGATGGCTTCGCAACTACATCGGT GGAGTCTTGCTCTACTTTATCTCTGGGTTTCTTTGGTGCTTCTACATCTA CTACTTAAAACGCAATGTTTATCTACCTAAAGGAATTCCCAATTGGTAA GGAAATAATTATTTTCTTTTTTCCTTTTAGTATAAAATAGTTAAGTGATG TTAATTAGTATGATTATAATAATATAGTTGTTATAATTGTGAAAAAATA ATTTATAAATATATTGTTTACATAAACAACATAGTAATGTAAAAAAATA TGACAAGTGATGTGTAAGACGAAGAAGATAAAAGTTGAGAGTAAGTAT ATTATTTTTAATGAATTTGATCGAACATGTAAGATGATATACTAGCATT AATATTTGTTTTAATCATAATAGTAATTCTAGCTGGTTTGATGAATTAAA TATCAATGATAAAATACTATAGTAAAAATAAGAATAAATAAATTAAAA TAATATTTTTTTATGATTAATAGTTTATTATATAATTAAATATCTATACC ATTACTAAATATTTTAGTTTAAAAGTTAATAAATATTTTGTTAGAAATTC CAATCTGCTTGTAATTTATCAATAAACAAAATATTAAATAACAAGCTAA AGTAACAAATAATATCAAACTAATAGAAACAGTAATCTAATGTAACAA AACATAATCTAATGCTAATATAACAAAGCGCAAGATCTATCATTTTATA TAGTATTATTTTCAATCAACATTCTTATTAATTTCTAAATAATACTTGTA GTTTTATTAACTTCTAAATGGATTGACTATTAATTAAATGAATTAGTCG AACATGAATAAACAAGGTAACATGATAGATCATGTCATTGTGTTATCAT TGATCTTACATTTGGATTGATTACAGTTGGGAAATTGGGTTCGAATCTA GACTTTAGGTAGATAAACATTGCGTTTTAAGTAGTAGATGTAGAAGCAC CAAAGAAACCCAGAGATAAAGTAGAGCAAGACTCCACCGATGTAGTTG CGAAGCCATCCTTGAAACCAATGAGGGAGTGGTCCCCACCATGATTCC GGCAAGAATGTGCCCAGAACAATCCTATTAAAAAACGACGTCTCCTCT ACAAATAAATTCAAGTAGTCGTCCATCGACGATTCAGTAGATTCCGATG G G A G A T G A T C C. G A G A A G A G A G A G A TT T G C. A G A A A G T A A C A A A G A G G T TAGTGGGGCACACA ATTTTTTAGATTTCTTTGTTGACTTGTCACAAC AG TAGTGTTAATTGTTGTGATCTGGCTGTGTAGCTGGGATCC

[0071 ] SEQ ID NO: 16 depicts sequence of hairpin structure generated by construct 2.

CTCGAGTGCTCTCTTATTCATAGAAGCCATATGGACTGCAAATATTCATG ACTGTATACATGCGAAGGTTTGGCCTGTAATGGGTGCCGGTTACCATACC ATCCACCATACTACGTACCGCCATAATTATGGTCACTACACAATATGGAT GGACTGGATGTTTGGAACTCTTCGCGATCCTGTTGAAGATGAAGTGAAGA AACTGTAAC ATTCATCCCTGTAACG A ATTGTTATTCATCGTCTTATTTATT AGGTTGCAGAGTGGTTGGTGCTTCATTTAGAGTTTGTTGTGTGTGCATTTC ATGGATGTAAATTTTACTAGTGGGTTTTCAATGTTTAGACAAAAAATATT ATCCAGGAAAAATACTGTGAAATGCTCTTGATGCATTTGAGGTATTGTTA TTGAGGAAAGAAGCAAGAGATCCAAGGAATTCCCAATTGGTAAGGAAAT AATTATTTTCTTTTTTCCTTTTAGTATAAAATAGTTAAGTG ATGTTA ATT A GTATGATTATAATAATATAGTTGTTATAATTGTGAAAAAATAATTTATAA ATATATTGTTTACATAAACAACATAGTAATGTAAAAAAATATGACAAGTG ATGTGTAAGACGAAGAAGATAAAAGTTGAGAGTAAGTATATTATTTTTAA TGAATTTGATCGAACATGTAAGATGATATACTAGCATTAATATTTGTTTTA ATCATAATAGTAATTCTAGCTGGTTTGATGAATTAAATATCAATGATAAA ATACTATAGTAAAAATAAGAATAAATAAATTAAAATAATATTTTTTTATG ATTAATAGTTTATTATATAATTAAATATCTATACCATTACTAAATATTTTA GTTTAAAAGTTAATAAATATTTTGTTAGAAATTCCAATCTGCTTGTAATTT ATCAATAAACAAAATATTAAATAACAAGCTAAAGTAACAAATAATATCA AACTAATAGAAACAGTAATCTAATGTAACAAAACATAATCTAATGCTAAT ATAACAAAGCGCAAGATCTATCATTTTATATAGTATTATTTTCAATCAAC ATTCTTATTAATTTCTAAATAATACTTGTAGTTTTATTAACTTCTAAATGG ATTGACTATTAATTAAATGAATTAGTCGAACATGAATAAACAAGGTAACA TGATAGATCATGTCATTGTGTTATCATTGATCTTACATTTGGATTGATTAC AGTTGGGAAATTGGGTTCGAATCTAGACTTGGATCTCTTGCTTCTTTCCTC AATAACAATACCTCAAATGCATCAAGAGCATTTCACAGTATTTTTCCTGG ATAATATTTTTTGTCTAAACATTGAAAACCCACTAGTAAAATTTACATCC ATGAAATGCACACACAACAAACTCTAAATGAAGCACCAACCACTCTGCA ACCTAATAAATAAGACGATGAATAACAATTCGTTACAGGGATGAATGTT ACAGTTTCTTCACTTCATCTTCAACAGGATCGCGAAGAGTTCCAAACATC CAGTCCATCCATATTGTGTAGTGACCATAATTATGGCGGTACGTAGTATG GTGGATGGTATGGTAACCGGCACCCATTACAGGCCAAACCTTCGCATGTA TACAGTCATGAATATTTGCAGTCCATATGGCTTCTATGAATAAGAGAGCA GGATCC [0072] In an embodiment of the present disclosure, there is provided a cDNA fragment encoding a polypeptide having amino acid sequence as set forth in SEQ ID NO: 2.

[0073) In a preferred embodiment of the present disclosure, there is provided a cDNA fragment as described herein, wherein said cDNA fragment has a polynucleotide sequence as set forth in SEQ ID NO: 1.

[0074] In an embodiment of the present disclosure, there is provided a recombinant DNA construct comprising a transcribeable polynucleotide fragment encoding a polypeptide having amino acid sequence as set forth in SEQ ID NO: 2, said transcribeable polynucleotide fragment operably linked to a heterologous promoter.

[0075] In a preferred embodiment of the present disclosure, there is provided a recombinant DNA construct as described herein, wherein said transcribeable polynucleotide fragment having polynucleotide sequence as set forth in SEQ ID NO: 1.

[0076] In a preferred embodiment of the present disclosure, there is provided a recombinant DNA construct as described herein, wherein said promoter is selected from the group of constitutive promoters, tissue specific promoters, and endogenous promoters.

[0077] In an embodiment of the present disclosure, there is provided a recombinant DNA vector comprising the recombinant DNA construct as described herein.

[0078] In an embodiment of the present disclosure, there is provided a recombinant DNA vector comprising the recombinant DNA construct comprising a transcribeable polynucleotide fragment encoding a polypeptide having amino acid sequence as set forth in SEQ ID NO: 2, said transcribeable polynucleotide fragment operably linked to a promoter.

[0079] In an embodiment of the present disclosure, there is provided a recombinant host cell comprising the recombinant DNA vector comprising the recombinant DNA construct comprising a transcribeable polynucleotide fragment encoding a polypeptide having amino acid sequence as set forth in SEQ ID NO: 2, said transcribeable polynucleotide fragment operably linked to a promoter. [0080| In a preferred embodiment of the present disclosure, there is provided a recombinant host cell as described herein, wherein said recombinant host cell is of bacterial or fungal origin.

[0081] In a preferred embodiment of the present disclosure, there is provided a recombinant host cell as described herein, wherein said recombinant host cell is Agrobacterium.

[0082] In an embodiment of the present disclosure, there is provided a recombinant host cell comprising the recombinant DNA construct comprising a transcribeable polynucleotide fragment encoding a polypeptide having amino acid sequence as set forth in SEQ ID NO: 2, said transcribeable polynucleotide fragment operably linked to a promoter.

[0083] In a preferred embodiment of the present disclosure, there is provided a recombinant host cell as described herein, wherein said recombinant host cell is of bacterial, fungal or plant origin.

[0084] In an embodiment of the present disclosure, there is provided a recombinant host cell encoding a transcribeable polynucleotide fragment encoding a polypeptide having amino acid sequence as set forth in SEQ ID NO: 2, wherein said transcribeable polynucleotide fragment has polynucleotide sequence as set forth in SEQ ID NO: 1, and wherein said polypeptide has C-5 sterol desaturase enzyme activity.

[0085] In an embodiment of the present disclosure, there is provided a recombinant host cell as described herein, wherein said recombinant host cell is selected from the group consisting of tomato, rice, wheat, and soybean.

[0086] In an embodiment of the present disclosure, there is provided a method of producing a transgenic plant, said method comprising: (a) transforming a plant cell with a recombinant DNA construct as described herein; (b) selecting a transgenic plant cell comprising said recombinant DNA construct; and (c) developing a transgenic plant, wherein said transgenic plant has enhanced physiological characteristics selected from the group consisting of drought tolerance, pathogen resistance, and nutritional quality. [0087 j In an embodiment of^" the present disclosure, there is provided a method of producing a transgenic plant, said method comprising: (a) transforming a plan! cell with a recombinant host cell as described herein; (b) selecting a transgenic plant cell comprising said recombinant host cell; and (c) developing a transgenic plant, wherein said transgenic plant has enhanced physiological characteristics selected from the group consisting of drought tolerance, pathogen resistance, and nutritional quality.

[0088] In a preferred embodiment of the present disclosure, there is provided a method as described herein, wherein said transgenic plant is a monocot or a dicot.

[0089] In a preferred embodiment of the present disclosure, there is provided a method as described herein, wherein monocot is selected from the group consisting of rice, and wheat.

[0090] In a preferred embodiment of the present disclosure, there is provided a method as described herein, wherein said dicot is selected from the group consisting of tomato, and soybean.

[0091] In a preferred embodiment of the present disclosure, there is provided a transgenic plant or parts thereof including seeds prepared by a method of producing a transgenic plant, said method comprising: (a) transforming a plant cell with a polynucleotide fragment comprising a cDNA fragment encoding a polypeptide having an amino acid sequence as set forth in SEQ ID NO: 2; (b) selecting a transgenic plant cell expressing a polypeptide encoded by said cDNA fragment; and (c) developing a transgenic plant, wherein said transgenic plant has enhanced physiological characteristics selected from the group consisting of drought tolerance, pathogen resistance, and nutritional quality.

[0092] In a preferred embodiment of the present disclosure, there is provided a transgenic plant as described herein, wherein said transgenic plant or parts thereof including seeds is selected from the group consisting of rice, wheat, tomato, and soybean.

[0093] In an embodiment of the present disclosure, there is provided a transgenic plant or parts thereof including seeds comprising a genome encoded polynucleotide sequence encoding a polypeptide having amino acid sequence as set forth in SEQ ID NO: 2, where in said genome encoded polynucleotide sequence has polynucleotide sequence as set forth in SEQ I D NO: I .

[0094] In an embodiment of the present d isclosure, LeCSSD from tomato shows 32% homology to FvC5SD with conserved three h istidine rich moti fs common to members of FA hydroxylase super family.

[0095] In an em bod iment of the present d isclosure, Lec5SD complemented plant were more in length as compared to dwarf mutants including increase in silique, root and leaf length.

[0096] In an embodiment of the present disclosure, localization study by particle bombardment of onion peel with LcC5SD-GFP construct shows sub-cellular localization of LeC5SD in on ion epidermal peel to the outer cell membrane and nuclear envelope.

[0097] In an embodiment of the present disclosure, expression of LeC5SD decreased significantly in RNAi tomato transgenics whereas overexpressed lines showed much higher expression of LeCSSD as compared to control.

[0098] In an embod iment of the present disclosure, RNAi lines are much susceptible to various stresses like drought and pathogen stress (infection by phytopathogen S. sclerotiorum) compared to wild type control.

[0099] In an embodiment of the present disclosure, over-expression lines were found to be more tolerant than wild type as well as that expressing ¥ C5SD for drought and pathogen stress.

[00100] In an embodiment of the present disclosure, expression of endogenous LeC5SD in wild type plants under drought stress increased significantly in leaves.

[00101 ] In an embodiment of the present disclosure, leaves from over-expression lines subjected to scanning electron microscopy showed ~ 32% more epicuticular wax compared to wild type leaves which is significantly higher than tomato transgenic expressing FvC5SD (=23%).

[00102] In an embodiment of the present disclosure, leaves from transgenic rice showed more epicuticular wax accumulation than wild type control. [001031 In an embodiment of the present disclosure, quantitative determination of isolated leaf epicuticular wax by gas chromatography-mass spectrometry (GC-MS) confirmed the increase of total wax content by =--26%.

[00104] In an embodiment of the present disclosure, transgenic plants (PB1) expressing LeC5SD were also more tolerant to drought stress compared to untransformed control.

[00105] Although the subject matter has been described in considerable detail with reference to certain preferred embodiments thereof, other embodiments are possible. EXAMPLES

[00106] The disclosure will now be illustrated with working examples, which is intended to illustrate the working of disclosure and not intended to take restrictively to imply any limitations on the scope of the present disclosure. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood to one of ordinary skill in the art to which this disclosure belongs.

Example 1

Materials, media and growth condition -

[00107] The Escherichia coli DH5a strain (used for DNA manipulation) was grown in LB medium. Tomato plants (Pusa ruby) were maintained in Murashige and Skoog medium at 23°C ± 2. Light was provided by cool white fluorescent tube lights with intensity 50-70 ^iEm^'2sec^"' in racks of plant growth room (16hrs light/8. Ohrs dark). Rice (Pusa basmatil) calli were maintained at 27 ± 1°C.

Example 2

Rice transformation

Callus induction

[00108] Mature dry seeds of rice cultivar Pusa basmatil (PB1) were surface- sterilized with 70% ethanol (v/v) for 1 min, followed by 30 min in 50% (v/v) commercial bleach with shaking at 180 rpm. Seeds were then washed 8-10 times with sterile distilled water and dried on autoc!aved Whatman paper (3 mm) for 5 min. For callus induction, twelve to thirteen seeds were inoculated per petriplate on callus induction medium (MCI- MS basal salts and vitamins (Caisson laboratories, Catalog no. MSP09) supplemented with 30 g/1 maltose, 0.3 g/1 casein hydrolysate, 0.6 g/1 L-proline, 3.0 mg/l 2, 4-D, 0.25 mg/l BAP, pH 5.8 and 3 g/1 phytagel. ) and incubated at 27 ± l°C in dark. MCI was prepared using basal MS salts containing all vitamins supplemented with 30 g/1 maltose, 0.3 g/1 casein hydrolysate, 0.6 g/1 L- proline, 3.0 mg/l 2,4-dichlorophenoxyacetic acid (2,4-D), 0.25 mg/l 6- benzylaminopur^'me (BAP), gelled with 3.0 g/1 phytagel and pH adjusted to 5.8 before autoclaving. After 14 days in dark, non-embryogenic calli (compact, non- friable calli that develop root like structures) were discarded and only embryogenic calli were selected. These embryogenic calli were cut into approximately 3 equal halves and sub-cultured again onto fresh MCI and kept for 4 days (dark, 27 ± 1°C) before transformation with Agrobaclerium tumefaciens.

Agrobaclerium strains and construct used for transformation

[00109] FvC5SD cloned in the binary Ti vector pBl 121 was used for rice transformation. It was transformed in Agrobaclerium tumefaciens strain EHAI05. This vector has kanamyin genes as the selectable markers.

Preparation of Agrobaclerium culture

[00110] Primary culture of Agrobaclerium was prepared by inoculating single colony from a freshly streaked plate, in 5 ml of autoclaved liquid YEP medium (10 g/1 bactopeptone, 10 g/1 yeast extract, 5 g/1 sodium chloride, pH 7.0) supplemented with 10 mg/l rifampicin and 50 mg/l kanamycin. The culture was incubated for 16- 20 h on a rotatory incubator shaker at 200 rpm in dark at 28°C. Secondary culture was prepared in a 500 ml baffled flask containing 100 ml YEP medium (supplemented with same antibiotics as used for primary culture) by adding 0.4% of the primary culture and grown under similar conditions. Once the O.D.₆ooreached -1.0, Agrobaclerium cells were pelleted by centrifugation at 8000 ^χ g for 15 min at 4°C. The cells were resuspended in MS resuspension medium containing 150 μΜ acetosyringone (MS salts, 68 g/1 sucrose, 36 g/1 glucose, 3 g/1 KCI, 4 g/1 MgCl₂, pH 5.2) to adjust the O.D.6ooof the bacterial suspension to 0.3.

Co-cultivation and selection

[00111] The 4 day subcultured embryogenic calli were collected and Agro-infected by immersing them in the Agrobaclerium culture for 20-25 min with intermittent gentle shaking at 50 rpm. The Agro-infected calli were dried on sterile Whatman No.3 filter paper for 5 min. Calli were then transferred to the co-cultivation medium ( CC )-MCI containing 10 g/l glucose, i 5.2, 150 μΜ acetosyringone and incubated at 27 ± l°C in the dark for around 48 hours. Once slight growth of Agrobactcri in appeared around most of the calli, the calli were rinsed 8-10 times with 250 mg/l cefotaxime in sterile distilled water, dried on sterile Whatman No.3 filter paper and transferred onto first selection medium-MS (MCI containing 250 mg/l cefotaxime and 50 mg/l kanamyin) and incubated for 12 days at 27 ± 1°C in dark. After the first selection, brown or black calli were removed and only creamish healthy calli were shifted to the fresh MSM media for second selection and maintained at 27 ± 1°C in dark. After second selection for 10 days, microcalli could be observed which were finally transferred to fresh MSM media for third selection and allowed to proliferate for 5 days at 27 ± 1°C in dark.

Regeneration

[00112] After third selection, black or brown microcalli were discarded and only granular 'macrocalli' were transferred onto two different media containing either two or three growth regulators viz. MSRMa and MSRMb. MSRMa comprised of MS salts,.30 g/l maltose, 2 mg/l kinetin, 0.2 mg/l naphthalene acetic acid (NAA), pH 5.8; 250 mg/l cefotaxime and 50 mg/l kanamycin added after autoclaving. While MSRMb consisted of MS salts, 30 g/l maltose, 2.7 mg/l BAP, 1.2 mg/l kinetin, 0.5 mg/l NAA, pH 5.8; 250 mg/I cefotaxime and 50 mg/l kanamycin added after autoclaving. Both MSRMa and MSRMb were supplemented with either 8 or 10 g/l agarose during the first phase and 4, 8 or 10 g/l agarose in the second phase of regeneration. These microcalli were incubated at 27 ± 1°C in dark for 7 days for the first phase of regeneration. During the second phase of regeneration, these were shifted to fresh regeneration medium with different concentration of agarose (8g/l ) and incubated in light for 4 days. Plantlets were than transferred to rooting medium (MROM-Half strength MS salts (MSP09), 30 g/l sucrose, pH 5.8, 3 g/l phytagel; 250 mg/l cefotaxime and 50 mg/l kanamycin added after autoclaving.

[00113] Figure 1 depicts stages of rice transformation; Figure 1(A) depicts callusing; Figure 1(B) depicts agroinfection; Figure 1(C) depicts selection; Figure 1(D) depicts regeneration; Figure I (E) depicts regeneration 2; and Figure 1(F) depicts transformed rice plants transferred to pots.

Example 3

Cloning of cDNA of LeCSSD and sequence analysis

[00114] LeC5SD cDNA was amplified from total cDNA by R T PCR (reverse transcription) of mRNA isolated from tomato leaves using the forward (SEQ ID NO: 3) and reverse (SEQ ID NO: 4) primers and was cloned into pGE T easy vector (Promega) and sequenced using Ml 3 forward and reverse primers. Analysis of the derived sequence by the blastx (wwww.ncbi.nlm.nih.gov) identified it to belong to FA hydroxylase superfamily. Protein sequences were deduced by back translation. Related protein sequences from other species were taken and CLUSTAL W and phylogenetic analysis (MEGA4) were performed. cDNA of LeC5SD consist of 816 bp sequence with deduced amino acid sequence of 271 a. a.

[00115] Figure 2 depicts sequence alignment between C-5 Sterol desaturase from tomato (LeC5SD) and Flammidina velittipes (FvC5SD). It can be inferred from the data that LeCSSD from tomato shows 32% homology to F C5SD with conserved three histidine rich motifs (involved in iron binding) common to members of FA hydroxylase super family. LeC5SD and FvC5SD, both the gene consists of two introns.

[00116] Figure 3(A) depicts that LeCSSD consists of larger size introns (603& 848bp). Figure 3(B) depicts that FvC5SD has smaller introns of (44bp and 53bp). Example 4

Phenotypic complementation in Arabidopsis dwar/7 mutant

[00117] LeC5SD cDNA was cloned in pCAMBIA1301 vector under CaMV 35S promoter. The construct was transformed in Dw/7 mutant of Arabidopsis by floral dip method and transformants were selected by hygromycin resistance. Healthy Arabidopsis plants were grown until they were flowering under long days in pots in soil covered with bridal veil, window screen or cheesecloth. Optimal plants have many immature flower clusters and not many fertilized siliques. Agrobacterium tumefaciens strain carrying gene of interest on a binary vector were prepared. A large liquid culture was grown at 28°C in LB with antibiotics to select for the binary plasmid, or grow in other media till mid-log phase. Agrobacieriitm cells were pelleted and resuspended to ΟΙ¾οο ⁼ 0-8 (can be higher or lower) in 5% Sucrose solution (100-200 ml) for each two or three small pots to be dipped, or 400-500 ml for each two or three 3.5" (9cm) pots. Before dipping, Silwet L-77 was added to a concentration of 0.05% (500 μΙ/L) and mixed well. Above-ground parts of plant were dipped in Agrobacterium solution for 2 to 3 seconds, with gentle agitation. A thin film of liquid coating the plant was visible. Dipped plants were placed under a dome or cover in dark for 16 to 24 hours to maintain high humidity (plants can be laid on their side if necessary). Plants were then grown normally, tying up loose bolts with wax paper, tape, stakes, twist-ties, or other means. Watering was stopped as seeds become mature. Dry seed were harvested. Transformants were selected using antibiotic or herbicide selectable marker.

[00118] Figure 4 depicts phenotypic complementation of dwf7 mutant of Arabidopsis Figure 4(A) depicts phenotypic difference in stems in dwf7 mutant and Lec5SD complemented plant. It can be inferred from the figure that Lec5SD complemented plants have longer stems compared to the dwf7 mutant. Figure 4(B) depicts phenotypic difference in roots in dwf7 mutant and Lec5SD complemented plant. It can be inferred from the figure that Lec5SD complemented plants have longer roots compared to the dwf7 mutant. Figure 4(C) depicts phenotypic difference in silique in dwf7 mutant and Lec5SD complemented plant. It can be inferred from the figure that Lec5SD complemented plants have longer silique compared to the dwf7 mutant. Figure 4(D) depicts phenotypic difference in leaves in dwf7 mutant and Lec5SD complemented plant. It can be inferred from the figure that Lec5SD complemented plants have longer leaves compared to the dwf7 mutant. Figure 4(E) depicts a comparison of plant length in dwf7 mutant and Lec5SD complemented plant. It can be inferred from the figure that Lec5SD complemented plants are longer compared to the dwf7 mutant.

[00119] Figure 4(F) sub-cellular localization of LeC5SD in onion epidermal peel with LeC5SD-GFP construct; Figure 4(G) depicts an image of phase contrast microscopy for sub-cellular localization of LeC5SD in onion epidermal peel with LeC5SD-G FP construct; in accordance w ith an embodiment of the present d isclosure.

Exam ple 5

RNAi constructs

[00120] Two RNAi constructs were prepared targeting different regions of LeCSSD (383 and 434bp). For construct 1 , the fragments of 383bp was ampli fied using forward primer (SEQ ID NO: 5 ) and reverse primer (SEQ ID NO 6 and cloned in sense direction in Xhol -EcoRI restriction sites of pHANNIBAL vector. Antisense fragment was ampl ified using forward primer (SEQ ID NO: 7) and reverse primer (SEQ ID NO: 8) cloned in Xbal- BamHI restriction sites.

[00121 ] For construct 2, the fragments of 434bp was amplified using forward primer (SEQ ID NO: 9) and reverse primer (SEQ ID NO: 10) and cloned in sense direction in Xhol -EcoRI restriction sites of pHANNIBAL vector. Antisense fragment was amplified using forward primer (SEQ ID NO: 1 1 ) and reverse primer (SEQ ID NO: 12) cloned in Xbal- BamHI restriction sites.

[00122] Entire cassette with CaMV35S was released from pHANNIBAL vector backbone using ECoRV enzyme and cloned in same site of pART27 binary vector. Example 6

Tomato transformation

[00123] The binary Ti vector pBI 121 was used for tomato transformation. LeC5SD gene was amplified using the forward (SEQ ID NO.: 13) and the reverse (SEQ ID NO: 14) primers. The GUS gene of the binary vector was replaced with the LeC5SD gene at the Xbal and Sad restriction sites to gain the new expression construct LeC5iSZ)-pBI 121 which was electroporated into Agrobacterhim tamefaciens strain EHA 105.

[00124] Transgenic plants were regenerated by Agrobacterium mediated transformation of tomato cotyledon leaves. After cutting, explants were placed on MS media (sigma) containing zeatin ( 10μg/m l) as callusing and shooting hormone (shooting media) and kept for one day under tissue culture conditions (24°C, 65% relative hum idity, 14/10 hr l ight-dark cycle). After one day these explants were used for transformation. Agrobacterium were grown in YEP medium for transformation. Agrob cteriitni cells were pellet suspended in liquid MS containing acetosyringone. The cell suspension were added to explants and co-cultivated. After co-cultivation, explains were transferred to MS (shooting media) and kept at 28°C. After two days, explains were transferred to shooting media containing cefotaxime and maintained at tissue culture conditions. Then explains were transferred to shooting media containing cefotaxime and kanamycin and maintained in this media for two to three and half months with regular change. Shoots (3-4cms in length) were then transferred to rooting media with hormone IAA (lO^ig/ml) and antibiotics and maintained for 1-2 months. Leaves were collected from rooted plants for DNA extraction (CTAB method) and PCR was performed with gene specific primers to determine putative transfonnants. 7-10% frequency of regeneration was achieved through this Ag obacterium mediated gene transfer method. PCR positive plants were transferred to green house after hardening. Transgene expression was further confirmed by Northern blot analysis or quantitative realTime PCR.

Example 7

Functional characterization of LcC5SD

[00125] For functional characterization of LQC5SD, tomato knockouts for Delta (7)- sterol-C5 (6)- desaturase were generated through RNAi strategy. Selected regions of LeC5SD were cloned in both sense and anti-sense direction in pART27 binary vector (CaMV35S promoter and kanamycin as selection marker) with PDK intron in between, to facilitate formation of hairpin which in turn will mediate RNAi mediated silencing of LeC5SD transcript.

[00126] Figure 5(A) depicts a schematic showing RNAi strategy. Tomato transgenic over-expressing the gene LeC5SD was generated. For this, LeC5SD gene was cloned in pB1121 binary vector under cauliflower mosaic virus 35S constitutive promoter (CaMV35S). Figure 5 (B) depicts a binary vector pB 1121 used for plant transformation. The transgene integration of tomato LeC5SD overexpressing transgenic lines and RNAi lines was done by PCR using gene specific as well as CaMV and PDK intron primers. Figure 5(C) depicts PCR to confirm transgene integration with gene and vector specific primers. Figure 5(D) depicts northern analysis for expression of LeC5SD gene (WT: wild type; Ox: over-expression lines). Northern blot analysis showed that the expression of LeC5SD decreased significantly in RN vi tomato transgenics whereas overexpressed lines showed much higher expression as compared to control. Further, analysis showed that RNAi lines are much susceptible to various stresses like drought and pathogen stress (infection by phytopathogen S. selerotiorum) compared to wild type control.

Example 8

Pathogenesis assay with S. selerotiorum and trypan blue staining

[00127] S. selerotiorum infection was carried out by the mycelium agar disc method on detached leaf. Mycelial agar plugs of 3.0 mm diameter punched from growing margins of a 4-day-old S. selerotiorum culture was applied on the adaxial surface of the leaves. Leaves were kept under 16-h photoperiod and 100% humidity. The disease symptoms were observed every 24 hrs, over a period of 1 week. This experiment was repeated three times under similar conditions.

[00128] For trypan blue staining, infected leaves were stained with 0.05% Trypan blue for 45 min and washed with PBS. All samples were viewed under light microscopy at 40X magnification.

[00129] Figure 6 depicts pathogenesis assay of transgenic plants with Scelrotinia selerotiorum; [Figure 6(A)] on the day of inoculation; [Figure 6(B)] on the fifth day of inoculation.

[00130] Figure 7 depicts trypan blue staining of fungal mycelia; [Figure 7(A)] in the uninfected leaf; [Figure 7(B)] in the infected leaf; and [Figure 7(C)] in the fungal mycelial disc.

[00131] Figure 8 depicts drought tolerance assay; [Figure 8(A)] in the RNAi lines; [Figure 8(B)]; in the overexpression lines.

It can be inferred from the above figures that over-expression lines were found to be more tolerant than wild type as well as that expressing

for drought and pathogen stress.

[00132] Figure 9(A) depicts expression level of endogenous LeC5SDmRNA in drought induced stress as determined by qRT-PCR. It can be inferred from the data that the expression of endogenous LeC5SD in wild type plants under drought stress increased significantly in leaves. [00133] Figure 9(B)/C) depicts wax content of leaf cuticular waxes of wild type and transgenic lines as determined by GC-iYIS. It can be inferred from the data that leaves from over-expression lines subjected to scanning electron microscopy showed ~ 32% more epicuticular wax compared to wild type leaves which is significantly higher than tomato transgenic expressing FvC5SD (=23%).

Exam le 9

Atomic absorption spectroscopy fo determination of total iron content

[00134] Samples (2.0 gm) were dried by lyophilisation and 20 ml of acid mixture (= cone, nitric acid: cone, perchloric acid: 4: 1) was added to it and evaporated to near dryness on a hot plate. The above procedure was repeated for samples until the fumes and sediment became white. After cooling, 5 ml of cone, hydrochloric acid was poured on the sediment. The samples were boiled for 5 minutes and allowed to dry and cool. After cooling, the sediments were quantitatively transferred in 100 ml volumetric flask dissolving the sediments into sterile water. Then these were filtered twice and kept in polypropylene bottles. The concentration of iron was determined by flame atomic absorption spectrometry using Spectra AA 55 spectrophotometer (Varian, USA; provided by Institution of Environmental Studies and Wetland Management, Kolkata). Figure 9(D) depicts total iron content as determined by atomic absorption spectrometry. It can be inferred from the data that the total iron content as measured by atomic absorption spectroscopy was also increased by 3 to 4 fold which is comparatively more than transgenics expressing ¥vC5SD.

[00135] Figure 9(E) depicts quantitation of polyunsaturated fatty acid in wild type and transgenic lines as determined by GC-MS. It can be inferred from the data that increase in beneficial polyunsaturated fatty acid (PUFA) was also higher than transgenics expressing FvC5SD. Thus, over-expression of endogenous C-5sterol desaturase gene in tomato (LeC5SD) is certainly more beneficial than expression of heterologous gene

This is presumably due to advantage of codon usage provided to endogenous gene than a fungal gene. These plants expressing L&C5SD will certainly be much safer for consumption.

Example 10 Epicuticular wax extraction and gas cli roinatogi a ph -mass spectrometry a nalysis (GC-MS analysis)

[00136] Leaves from one month old tomato or rice plants were i mmersed in 30 m l chloroform for 30s at room temperature. The same leaves were then re-extracted with chloroform at 60°C for 20s, and the two chloroform extracts containing wax were pooled. Chloroform was evaporated and five microgram of n-tetracosane (C24) was added to each sample as an internal standard. To the dried residue Ι ΟΟμΙ of derivatization reagent (80 μΙ BFSTA+ 20 μΙ TMCS) was added and incubated at 65°C for I hr. GC-MS analysis was performed with Ι Ι of the sample in spl it mode on Shimadzu GCMS-QP 2010 plus. The mass spectrometer was tuned according to the manufacturer's recommendations. GC was performed on an Rtx5MS- 30m column with 0.25-mm ID and 0.25μηι df (Restek). The injection temperature was set to 300°C, the interface temperature to 300°C, and the ion source adjusted to 250° C. Helium was used as the carrier gas at a flow rate of 1 ml min^{" 1}. The analysis was performed using the following temperature program: 1 min of isothermal heating at 100°C followed by heating at 300°C for 20 mins. Mass spectra were recorded at 2 scan sec^{" 1} with a scanning range of 4.0 to 850 m/z. Quantification was based on peak areas and normalization based on the internal standard.

[00137] Figure 10 depicts sequence alignment between C-5 sterol desaturase homolog from rice (Os01 g04260) and tomato (LeC5SD).

Example 11

Scanning electron microscopy (SEM)

[00138] For SEM examination, 0.5-cm segments were prepared from the appropriate region of the leaves from one month old tomato or rice plants. The samples were air dried for 72 hrs at room temperature, then mounted onto a copper holder with double adhesive carbon tape, sputter coated with gold for 3 min, and examined under an electron m icroscope (Zeiss).

[00139] Figure 1 1 (A) depicts scanning electron microscopy images of Pus a Basmati leaves showing epicuticular wax distribution. It can be inferred from the figure that Scanning electron microscopy of leaves from transgenic rice showed more epicuticular wax accumulation than wild type control. [00140] Figure I l(B and C) depict quantization of epicuticular wax from rice leaves by GC-MS. It can be inferred from the data that quantitative determination of isolated leaf epicuticular wax by gas chromatography-mass spectrometry (GC-MS) confirmed the increase of total wax content by -26%. Transgenic plants (PB1) expressing LeC5SD were also more tolerant to drought stress compared to untransformed control.

Example 12

Comparison of fungal gene vs. tomato gene in Arabidopsis

[00141] A comparison of fungal and tomato desaturase gene was performed in Arabidopsis. Figure 12(A) depicts sequence alignment between Arabidopsis Delta-7 C-5 sterol desaturase with C-5 sterol desaturase from tomato (Lec5SD). It can be inferred from the data that the Arabidopsis Delta-7 C-5 sterol desaturase shows very high identity of 79% to C-5 sterol desaturase from tomato (Lec5SD). Figure 12(B) depicts sequence alignment between Arabidopsis Delta-7 C-5 sterol desaturase with C-5 sterol desaturase from fungus. (FvC5SD). It can be inferred from the data that FvC5SD shows only 34% homology to Arabidopsis c-5 sterol desaturase. This was also reflected in the complementation study. The Arabidopsis dwf7 mutant is characterized by dwarf phenotype being deficient in brassinosteroid biosynthesis. When LeC5SX> cloned in plant expression vector pCAMBIA1301 was transformed in Arabidopsis by A gro bacterium mediated floral dip method, transformants showed partial rescue of dwarf phenotype. Figure 13(A) depicts silique, root and leaf length in dwf7 mutant; Figure 13(B) depicts silique, root and leaf length in FvC5SD complemented plant; Figure 13(C) depicts silique, root and leaf length in LeC5SD complemented plant. Transformants were more in length as compared to dwarf mutants including increase in silique, root and leaf length. However, the length was little less as compared to WT. However, when FvC5SD cloned in pBI 121 was transformed to dwf7mutant, the degree of rescue was very less as achieved by LeC5SD.

[00142] In conclusion, the present disclosure provides transgenic plants and methods for obtaining these plants that express a polypeptide with C-5 sterol desaturase activity centering enhanced drought tolerance, pathogen resistance, and nutritional quality to the transgenic plant.

Claims

f/VVe claim:

I. A cDNA fragment encoding a polypeptide having amino acid sequence as set forth in SEQ ID NO: 2.

2. The cDNA fragment as claimed in claim 1, wherein said cDNA fragment has a polynucleotide sequence as set forth in SEQ ID NO: 1.

3. A recombinant DNA construct comprising a transcribeable polynucleotide fragment encoding a polypeptide having amino acid sequence as set forth in SEQ ID NO: 2, said transcribeable polynucleotide fragment operably linked to a heterologous promoter.

4. The recombinant DNA construct as claimed in claim 3, wherein said transcribeable polynucleotide fragment having polynucleotide sequence as set forth in SEQ ID NO: 1.

5. A recombinant DNA vector comprising the recombinant DNA construct as claimed in any of the claims 3-4.

6. A recombinant host cell comprising a recombinant DNA vector as claimed in claim 5.

7. The recombinant host cell as claimed in claim 6, wherein said recombinant host cell is of bacterial or fungal origin.

8. The recombinant host cell as claimed in claim 7, wherein said recombinant host cell is Agrobacterium.

9. A recombinant host cell comprising a recombinant DNA construct as claimed in any of the claims 3-4.

10. The recombinant host cell as claimed in claim 9, wherein said recombinant host cell is of bacterial, fungal, or plant origin.

II. A recombinant host cell encoding a transcribeable polynucleotide fragment encoding a polypeptide having amino acid sequence as set forth in SEQ ID NO: 2, wherein said transcribeable polynucleotide fragment has polynucleotide sequence as set forth in SEQ ID NO: 1, and wherein said polypeptide has C-5 sterol desaturase enzyme activity.

12. The recombinant host cell as claimed in claim 11, wherein said recombinant host cell is selected from the group consisting of tomato, rice, wheat, and soybean.

13. A method of producing a transgenic plant, said method comprising:

:i. transforming a plant cell with a recombinant DNA construct as claimed in any of the claims 3-4, or a recombinant host cell as claimed in any of the claims 6-10;

b. selecting a transgenic plant cell comprising said recombinant DNA construct; and

c. developing a transgenic plant,

wherein said transgenic plant has enhanced physiological characteristics selected from the group consisting of drought tolerance, pathogen resistance, and nutritional quality.

14. The method as claimed in claim 13, wherein said transgenic plant is a monocot selected from the group consisting of rice, and wheat.

15. The method as claimed in claim 13, wherein said transgenic plant is a dicot selected from the group consisting of tomato, and soybean.

16. A transgenic plant or parts thereof including seeds prepared by a method as claimed in claim 13.

17. The transgenic plant or parts thereof including seeds as claimed in claim 16, wherein said transgenic plant or parts thereof including seeds is selected from the group consisting of rice, wheat, tomato, and soybean.

18. A transgenic plant or parts thereof including seeds comprising a genome encoded polynucleotide sequence encoding a polypeptide having amino acid sequence as set forth in SEQ ID NO: 2, wherein said genome encoded polynucleotide sequence has polynucleotide sequence as set forth in SEQ ID NO: 1.