Isolation And Functional Analysis Of LeFAD7 Gene In Tomato Under Temperature Stress

Temperature is a major environmental factor limiting plant growth, development and outputs. The biologic membrane was regarded as the position which is firstly suffered damage under temperature stresses. The content of unsaturated fatty acid in plant membrane lipids was higher, the temperature of transition of membrane lipids was lower and the chilling tolerance of plans was stronger. Contrarily, the temperature of transition of membrane lipids was higher and the thermal tolerance was stronger.Omega-3 fatty acid desaturase was the key enzyme which catalyzed 16:2 (7, 10) or 18:2 (9, 12) to form 16:3 (7, 10, 13) or 18:3 (9, 12, 15). The change of its content can influence the composition of membrane lipid, especially the level of TAs. Then it can affect the temperature of transition of membrane lipids and change the tolerance under temperature stresses.In this research, a full length cDNA of tomato chloroplastω-3 fatty acid desaturase gene was isolated from tomato using homological clone. The expression pattern and functional analysis showed that expression of the gene was induced by low temperature, water and salt stresses, whereas it was inhibited by heat stress. Interestingly, inhibition of this gene can improve the thermal tolerance of tomato plants under high temperature stress, and over-expression of the gene can enhance the chilling tolerance of tomato plants under low temperature stress. The main results are as follows:1. Two degenerate primers were designed to amplify specific DNA fragment using cDNA prepared from tomato leaves according to the homologous sequences from other plants. The middle fragment of interested cDNA was obtained by RT-PCR. Then the full length of the cDNA was isolated by 5′RACE and 3′RACE. The clone contains 1683 bp nucleotides with an open reading frame (ORF) of 1308 bp comprising 435 amino acid residues with the predicted molecular mass of 50 kD. Then these sequence data have been submitted to the GenBank databases under accession number AY157317 (address is as follows: http://www.ncbi.nlm.nih.gov).