The Study Of Enhancement Of Drought Tolerance In Cotton By Transgene Pyramiding Of ZmPLC1and BetA

Drought is a global natural disaster, it has seriously affected crop yield and quality. Cotton is a kind of important economic crops, which occupies an important position in the national economy. Along with the growing population and the emerging food crisis, the phenomenon that cotton and food crop compete for farmland is becoming more and more serious, growing cotton in salt and drought areas becomes a copying strategies. Utilizing genetic engineering to improve cotton stress resistance and yield is becoming a research focus.Abiotic stress, especially drought, is a complex response and probably involves many genes, with each individual gene playing a unique role in determining the overall tolerance of stress. Many of the transgenic plants produced in the past several years with single-gene transfer could only bring marginal stress tolerance, this makes the single gene transformation to significantly improve plant stress tolerance has become difficult and slow. Therefore, the combination of various components might enhance several the tolerance-related traits together in a single plant, so the gene pyramiding is a new strategy to obtain plants with high levels of stress tolerance in the future.Glycine betaine is important compatibility solute in plants, it plays an important role in osmotic protection, maintenance of biomacromolecules and membrane integrity and function, the protection of photosynthetic machinery and inducing specific gene expression. Glycine betaine to improve crop resistance has been widely proved. Phosphatidylinositol-specific phospholipase C (PI-PLC) plays a key role in the phosphatidylinositol signaling pathway and play an important role in the stress response and resistance. Enhanced expression of phospholipase C in transgenic maize improved drought tolerance has been proved. In this study, the transgenic pyramiding cotton plants which is consist of ZmPLC1and betA are obtained by co-transformation. The analysis of drought tolerance at the physiological level was performed. The transgene pyramiding plants showed higher drought tolerance than single gene transgenic plants.By PEG6000simulating osmotic stress in the seedling stage and the determination of various lines of photosynthetic, chlorophyll fluorescent indicator and relative water content and osmotic potential, we found that transgenic plants compared with wild type exhibited higher drought tolerance and the drought tolerance of the transgenic pyramiding lines is also higher than that of single gene transformation control lines. The transgene pyramiding has higher relative water content and lower osmotic potential, and the net photosynthetic rate was significantly higher than other lines, and has a lower damage of photosystem Ⅱ in the process of osmotic stress in seedling stage.In drought stress experiment of bud stage, the determination of a large number of plant stress-related phenotypes and physiological and biochemical processes determine the drought tolerance of plants. Compared with other transgenic lines, polymerization lines show a higher accumulation of osmolytes (glycine betaine, praline and soluble sugars), lower osmotic potential and maintain a higher relative water content. At the same time, leaf cells of transgenic pyramiding lines has higher activities of antioxidant enzymes (superoxide dismutase activity) and lower membrane damage (lower ion leakage and malondialdehyde content) which is of great significance in the response to drought stress under oxidative stress injury and maintainance of the normal function and stress tolerance of plant cells.Under drought stress, photosynthesis and chlorophyll fluorescence data also show that transgenic pyramiding lines have high drought tolerance.In drought stress experiment of flowering stage, through the compare of agronomic traits of each lines, we find that the stress in flowering stage can significantly reduce the plant height of cotton, flowering, flower number, the boll number and yield.While transgenic pyramiding lines has a higher cotton seed yield and lint yield compared with other transgenic lines, which is of great significance for the production practices.The results derived from drought stress experiment in seedling, budding and flowering stage show that the Zea mays phosphatidylinositol phospholipase C lgene (ZmPLCI) and E. coli choline oxidase gene (betA) can both increase the resistance of plants, the co-expression of ZmPLCI and betA in the same plant can further improve the drought tolerance of cotton. This also proved the feasibility of improving plant tolerance by transgenic pyramiding means, which is of great significance for cotton toleance appliance and theoretical research and provide excellent germplasm resources for the cultivation of new cotton varieties.