Functional Analysis Of Four Cold-Related Genes In Tomato

Low temperature stress cause major losses in crop productivity worldwidely. Tomato, as a thermophilic plant, is sensitive to cold. Plants vary greatly in their abilities to survive in low temperature. In this study, four cold related genes selected in base of our privous microarray analysis were transformed into cold-sensitive tomato cultivar LA4024 with over-expressioning. They are Geranylgeranyl reductase(GGR), xyloglucan endotransglycosylase (XET), phloem protein(P-p), and NAC2 genes relatively. With the help of molecular biological and physiological-biochemical methods we analyzed these gene functions under cold and salt stresses. This may help to achieve better tomato breeding program with cold stress tolerance. The main results were as follows:1. Four over-expression vectors were introduced into the genome of cold-sensitive tomato cultivar LA4024 through Agrobacterium mediated transformation, and we obtained 15 transgenic lines,18 transgenic lines,39 transgenic lines and 40 transgenic lines relatively by PCR identification.2. Four target genes were confirmed using RT-PCR and promoted in different transgenic lines.3. Tissue expression profile analysis using RT-PCR indicated that four target genes were expressed in all tested tissues constitutively, whereas the expression levels were different.4. Genetic segregation analysis was carried out on offspring of the transgenic plants. The different number of single-copy transgenic lines showed a 3:1 segregation pattern in Chi-square test.5. Salt tolerance was evaluated using detached leaf discs from Tj trangenic plants, and the Chlorophyll content of transgenic leaf discs decreased less than that of non-transformed ones.6. Cold tolerance were characterized in Ti trangenic plants, and chilling injury index, seedling damage rate and MDA contents were analyzed under cold stress. It was found that that overexpression of GGR, P-p could improve chilling stress tolerance on tomatos.7. Phenotypic changes such as leaf vein etiolation was observed after the third or forth true leaf in partial plants of two GGR overexpressing plants(GGR-5 GGR-7). In high temperature and strong light, leaf vein etiolation was observed in partial GGR-13 transgenic plants. With the seedling age goes on, leaf vein etiolation get worse until the whole plant.