The Functions Of ATHK1on PEG-induced Antioxidant Defence System In Arabidopsis Thaliana

Drought tolerance in plants is related to the responce of antioxidant defense system of cells during drought stress, of which the process is affected by the regulation of various signal components. ATHK1(At2g17820)has been suggested to act as an osmosensor in osmotic stress perception and has been implicated in drought and salt tolerance in Arabidopsis thaliana. However, the signal transduction mechanisms between ATHKl and osmotic stress-induced antioxidant defense system is not clear. In this study, the role of ATHK1in PEG-simulated drought stress-induced antioxidant defense systems was explored in ATHK1knock-out mutant (athkl) and wild-type (WT) of Ws. The main results are as follows:Firstly, the differences in drought tolerance were observed between mutant and wild type. During soil drying period, athkl mutant showed sensitive to soil drying. Great differences were also detected in water loss of detached leaves between athkl mutant in240minutes.Secondly, under12%PEG stress, the oxidative damage of athkl was obviously higher than that of wild-type, reflected by increased MDA, hydrogen peroxide (H2O2) and superoxide anion radical (O2·). In addition, the athkl seedlings also showed decreased activities of antioxidant enzymes ascorbate peroxidase (APX), catalase (CAT), peroxidase (POD) and Superoxide Dismutase (SOD) compared to wild-type.Thirdly, after6h of12%PEG treatment, the content of ABA increased55%,48%respectively in Ws and athkl, compared to the control. As expected, in wild-type seedlings, transcript abundance of ATHK1increased in the presence of12%PEG in6hours. In addition, the mRNA levels for NCED3and AAO3also increased in Ws, compared with athkl mutant.Finally, in the presence of PEG+ABA, both the level of MDA and the activities of antioxidant enzymes (APX, POD,SOD) recovered to the level of wild-type which treated with PEG alone.According to the above results and former research, it was suggested that ATHK1mediate the drought stress tolerance induced by PEG and athkl mutant is more sensitive to PEG stress partly because it had the lower ABA content than the wild-type.