The Overexpression Of GmNAC4 Gene Improves Salt Stress Tolerance In Transgenic Cotton

As a developing country, agriculture is one of the most important economic pillars in our country.Cotton industry occupies an important position in the agricultural economy,and with the rapid growth of textile exports,cotton supply and demand gap remains large.Because of the cultivated land resource constraints, contradiction between cotton cultivated land and grain cultivated land is becoming more and more serious.Based on the remarkable economic and social benefits of cotton industry, the development of saline upland cotton industry will effectively solve the problem that the utilization of saline-alkali land and contradiction between cotton cultivated land and grain cultivated land.Transcription factors can activate the expression of genes under stress to improve the resistance of plants.Many Studies had shown that NAC transcription factors can improve the plants resistance by stress response and hormone regulation, etc.By the technology of agrobacterium mediated transformation of shoot tips, we got the GmNAC4-overexpressed transgenic cotton. In this work, compared with wild type cotton Lu 21, we discussed salt resistance of transgenic cotton and the mechanisms of salt tolerance.At the four leaf stage of seedling under the 250 mm NaCl solution treatment after 21 days,compared with wild type cotton Lu 21, GmNA C^-overexpressed transgenic cotton G15,G21 and G31 had higher K+/Na+and can raise salt resistance; chlorophyll content of GmNAC4-overexpressed transgenic cotton was higher than wild type; GmNAC4-overexpressed transgenic cotton has the highest net photosynthetic rate at 20.65μmolCO2 m-2s-1, wild type controlled was only15.88 μmolCO2m-2s-1; SOD enzyme activity and osmotic protection of GmNAC4-overexpressed transgenic cotton increased significantly than wild type. GmNAC4-overexpressed transgenic cotton osmotic potential is lower than the wild type plants to keep higher integrity of the cell membrane.These biochemical index determination results show that the salt resistance of GmNAC4-overexpressed transgenic cotton is significantly higher than wild type.In the experiment of seed germination under salt stress, there was no significant difference between transgenic cotton and wild type cotton before salt stress;After 50 mM salt stress, GmNAC4-overexpressed transgenic cotton began to appear significant difference with wild type in germination rate and growth;In the process of 100mM to 250mM salt stress, germination rate of GmNAC4-overexpressed transgenic cotton and wild type is affected by salt stress to some content.And under 250 mM salt stress, GmNAC4-overexpressed transgenic cotton had a highest germination rate reached to 32.5% and the wild type is only 7.5%.This data show that germination rate of GmNAC4-overexpressed transgenic cotton is higher than the wild type.The salt tolerance analysis of leaves under 400mM and 600mM NaCl treatment showed that GmNAC4 transgentic lines had higher chlorophyll content than that of wild type.PCR and Southern blot detected GmNAC4 gene integrated into the cotton genome.In RT-PCR detection, the wild type did not detect GmNAC4. After salt treatment, GmNAC4 expression of transgenic cotton increased by 68.65%-91.45%; The GhSOD expression of transgenic cotton was higer than wild type by 6.54%-13.89%; The GhProDH expression was higher than wild type by 22.43%-33.72%; The GhAKT expression was higher than wild type by 25.47%; The GhSOS expression was higher than wild type by 18.63%-37.25%; The GhDGK expression was higher than wild type by 37.12%.These data indicated that salt resistance of GmNAC4-overexpression transgenic cotton increased significantly, this work provided a valuable resource for the cotton salt tolerance species breeding.