The Study Of Salt Tolerance In Cotton By Co-expressing Beta、ZmPIS And TsVP

The salt stress is one of the major factors that limit crop agriculture production. For crops, salt stress not only affects the whole growth proces, but also affects the production, so the study of salt-tolerant plant species is of great significance. Cotton is known as an important economic crop, cultivateing tolerant cotton varieties by genetic engineering and planting cotton in saline which is important for development and utilization of saline.Overexpression of genes coding choline dehydrogenase of Escherichia coli and phosphatidylinositol synthase of Maize and H+-PPase in vacuolar membrane of Salt mustard respectively can significantly improve the salt tolerance of plants. Since betA、TsVP and ZmPIS genes exist in the different metabolic pathway, whether co-expression of betA、TsVP and ZmPIS genes confer greater salt tolerance to transgentic plants is worth studing. Our studies aim at analysising the salt tolerance of betA-ZmPIS-TsVP transgentic cotton, betA、TsVP transgentics and none transgentics to explore the possible mechanism of improving salt tolerance by co-expression of betA-ZmPIS-TsVP. We expect selecting cotton plants which have greater salt tolerance.Our results showed that transgentic cotton lines 3G26、3G28 3G38,co-expressing betA-ZmPIS-TsVP genes showed greater salt tolerance under 250mM NaCl treatment in sandy soil condition than transgentic cotton line T expressing TsVP gene single、cotton line B expressing betA gene single and none transgentic line CK.Seeds of all betA-ZmPIS-TsVP transgentic lines germinated earlier and recorded a higher final germination percentage than betA、TsVP transgentics under more than 250mM NaCl treatment and the time to 50% enmergence of betA-ZmPIS-TsVP transgentic lines is less than that of betA or TsVP transgentics. The seedlings of betA-ZmPIS-TsVP transgentic lines grew better and had higher dry weight than that of TsVP transgentics and betA transgentics under 250mM NaCl treatment after 40 days of germination.Furthermore, compared with betA transgentics、TsVP transgentics and none transgentics, leaves of these betA-ZmPIS-TsVP transgentic lines also exhibited relatively higher K+/Na+ rate, ion content (Na+,Cl-,Ca2+), relative water content, chlorophfll content, net photosynthetic rate, solute sugar and proline content and antioxidant enzymes activity in 250 mM NaCl treatment, after 21 days. Besides, the osmotic potencial, membrance ion leakage and MDA level of betA-ZmPIS-TsVP transgentic lines were significantly higher than that of TsVP transgentics and none transgentics.In general, these results supported the hypothesis that co-expression betA、TsVP and ZmPIS genes confer greater salt tolerance to transgentic cotton plants than the single gene betA or TsVP. This proved the feasibility of improving plant tolerance by transgenic pyramiding means, which is of great significance for cotton toleance appliance and theoretical research and provides excellent germplasm resources for cultivating new salt-tolerant cotton varieties.