The Study Of Salt Tolerance In Cotton Co-expressin TsVP And AtNHX1

In recent years, there is a competition between grain and cotton production due to the limited resource of arable land. Salt stress is one of the important abiotic stress that seriously affcts the yield and quality of crops in china. Cotton is known as "pioneer crops" in saline. Selecting and planting cotton in saline which has more salt tolerance is important for solving that problem and development and utilization of saline.Overexpression of genes coding HT-PPase and Na+/H+antiporter in vacuolar membrane respectively can significantly improve the salt tolerance of plants. Since TsVP and AtNHXl genes exist in the same metabolic pathway, whether co-expression of TsVP and AtNHX1genes confer greater salt tolerance to transgentic plants than the single gene TsVP or not is worth studing. Our studies aim at analysising the salt tolerance of TsVP+AtNHX1transgentic cotton, TsVP transgentics and none transgentics to explore the possible mechanism of improving salt tolerance by co-expression of TsVP and AtNHX1. We expect selecting cotton plants which have greater salt tolerance.Our results showed that transgentic cotton lines AT5, AT11and AT27co-expressing TsVP and AtNHXl genes showed greater salt tolerance under250mM NaCl treatment in sandy soil condition than transgentic cotton line T18expressing TsVP gene single and none transgentic line CK. This is consistent with the result of experiment in saline in DongYing.Seeds of all TsVP+AtNHX1transgentic lines germinated earlier and recorded a higher final germination percentage than TsVP transgentics under more than150mM NaCl treatment and the time to50%enmergence of TsVP+AtNHXl transgentic lines is less than that of TsVP transgentics. The seedlings of TsVP+AtNHX1transgentic lines grew better and had higher dry weight than that of TsVP transgentics under250mM NaCl treatment after40days of germination.The analysis of salt tolerance of leaves under400mM and600mM NaCl treatment showed that TsVP+AtNHX1transgentic lines had higher chlorophyll content than that of TsVP transgentics and none transgentics.Furthermore, compared with TsVP transgentics and none transgentics, leaves of these TsVP+AtNHXl 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 in250mM NaCl treatment, after21days. Besides, the osmotic potencial, membrance ion leakage and MDA level of TsVP+AtNHX1transgentic lines were significantly higher than that of TsVP transgentics and none transgentics.In addition, the yield of TsVP+AtNHX1transgentic lines was significantly higer than the TsVP transgentics and none transgentics.In general, these results supported the hypothesis that co-expression TsVP and AtNHXl genes confer greater salt tolerance to transgentic cotton plants than the single gene TsVP. This proved the feasibility of improving plant tolerance by transgenic pyramiding means and provided excellent germplasm resources for cultivating new salt-tolerant cotton varieties.