Functional Characterization Of AtNEK6 Overexpression In Cotton Under Drought And Salt Stress

Cotton(G.hirsutum),as the world’s main source of natural fiber and seed oil,is grown in 70 countries.Cotton,like other crops,is also suffering severe biotic and abiotic stresses.Although conventional breeding,mutation breeding and pest management measures have improved the heat resistance,fiber quality and yield of cotton,biological and abiotic stresses such as diseases and insect pests,drought and salinization are still threatening the cotton industry.Adverse environment(such as low temperature,high temperature,drought and salting)will cause a series of physiological metabolic reactions in plants,which is manifested as reversible inhibition of metabolism and growth,and even cause irreversible damage,resulting in the death of the plant.The drought tolerance and salt tolerance of cotton are higher than other grain crops,With the contradiction between grain and cotton have become increasingly prominent,dry lands,saline-alkali lands that are not suitable for planting crops,and the coastal beaches are another choice for cotton cultivation.AtNEK6 encodes a serine / threonine protein kinase,which participates in the function of regulating cell cycle and is related to the growth and resistance of plants.In this study,through overexpression of AtNEK6 in cotton promoted the growth and development of cotton and improved its salt tolerance and drought tolerance.The main progress of this study is as follows:1.The AtNEK6 gene was transformed into cotton and the transgenic lines of T2 generation were obtained.The results of qRT-PCR detection showed that the gene was expressed in the roots,stems and leaves of transgenic cotton;2.Under normal culture conditions,compared to wild type plants,The height and leaf area increased in transgenic plants.Followed by no significant differences in epidermal cells of leaf area observation of leaf epidermal cells in scanning electron microscope between wild-type plants and transgenic plants.The expression of genes related to cell proliferation and growth in cotton was further examined.The results showed that the expression levels of these genes in the transgenic lines were higher than those in wild-type plants,indicating that AtNEK6 may promote plant growth and development through regulating the cell cycle and growth related genes;3.The roots of the plants were observed under sterile culture conditions.In the control group,the root length,fresh weight,and dry weight of the transgenic lines were not significantly different from those of the wild type,but the number of lateral roots of the transgenic lines was higher than that in the wild type.In the stress treatment group,the roots of the transgenic lines were significantly more developed than that in the wild type,and under the mannitol treatment,the root length,the number of lateral roots,the fresh weight and the dry weight of the transgenic lines were significantly increased.Under the NaCl treatment,the number of lateral roots,fresh weight,and dry weight of the transgenic lines increased significantly,but the root length of the transgenic plants was not significantly different from that of the wild type plants;4.In the salt and drought tolerance experiment,one-month-old transgenic plants and wild-type plants were treated with drought and salt stress.Among the drought-treated group,wild-type plants had more wilting than the transgenic lines.In the salt-stress treatment group,there was no wilting in the wild-type plants and the transgenic lines.The results of enzyme activity assays of SOD and CAT showed that the ability of the transgenic lines to remove superoxide and hydrogen peroxide was significantly better than that of wild-type plants.The results of MDA content detection showed that membrane lipid damage of transgenic lines was lower than that of wild-type plants;5.The expression of stress-related genes was detected by qRT-PCR.The results showed that the expression levels of GhAREB,GhDREB,GhNCED,and GhLEA5 were significantly increased in transgenic plants after stress treatment,suggesting that AtNEK6 may regulate the stress response process of plants by affecting multiple pathways,thus improving the drought and salt tolerance of plants.In conclusion,we conducted a systematic study about the expression of AtNEK6 in cotton.The results showed that,AtNEK6 promoted the growth and development of cotton by participating in the regulation of cell cycle and growth.In addition,AtNEK6 enhanced the salt tolerance and drought tolerance of cotton in adversity,and provide experimental basis for cultivating cotton materials with high quality and high resistance.