The Basic Function Analysis Of Vde Gene In Arabidopsis Under Drought

In order to elucidate the function of the violaxanthin de-epoxidase (vde) gene under water stress, we used vde gene deletion mutant of Arabidopsis, as well wild-type (Columbia) as materials, and measured photosynthesis, chlorophyll fluorescence parameters (such as net photosynthetic rate, stomatal conductance, transpiration rate, maximal photochemical efficiency, non photochemical quenching coefficient and so on), the parameters of the respiration, antioxidant enzyme activity and the change of xanthophyll cycle components under water stress in the present study. Especially, we assayed the changes of vde gene expression in Arabidopsis thaliana with mutants and wild type plants exposed to water stress. The main results are as follows:l.The deletion of vde gene accelerated the bolting and flowering time, decreased stomatal conductance and transpiration rate compared with the wild controls. Also, its respiration was inhibited to some extents. Cyclooxygenase VDE in mutant can not normally catalyze violaxanthin (V) to zeaxanthin (Z) As a result, the de epoxidation state (Z+0.5A)/V+A+Z decreased, and heat dissipation could not be proceeded normally. Accordingly, the non photochemical quenching coefficient (NPQ) decreased. We speculated that excess light energy cannot be dissipated, leading to the photoinhibition on plant, further impair PS II photoreaction center. Maximum photochemical efficiency Fv/Fm in mutant was lower than that in wild type.2. Under water stress, vde mutant had higher wilting levels, lower survival rate compared with wild type. The tendency of its photosynthetic, fluorescence parameters was similar with wild type, and slightly lower. During the drought treatment, NPQ increased in early period and then decreased over time.And NPQ was higher under high concentration PEG solution treatment than the other both vde mutant and wild type subject to a lower concentration of PEG3. Vde mutant changed the activity of antioxidant enzymes such as CAT. POD. and APX under water stress. During the drought treatment, the activity of POD in mutant was lower than that in wild type. It had been shown that under water stress, the activity of POD in vde mutant was lower than that in wild type. The enhanced activity of SOD and reduction of POD detected in the mutant may be attributed to the higher sensitivity of plants to water stress.4. The expression of alternative oxidase (AOX) gene was inhibited in vde mutant. During the drought treatment, the expression of aox was increased in early stage, and then decreased over time. As the key enzyme gene in encoding alternate breathing route, the increasing expression of aox could promote the accumulation of AOX, consequently enhance alternative respiration of plants. The tendency of aox expression level was consistent with the results of respiratory parameters determined in Arabidopsis.