Transcription factor WRKY46 regulates osmotic stress responses and stomatal movement tissue specifically and independently in Arabidopsis

Drought and salt stress severely inhibit plant growth and development. However, the regulatory mechanisms of plants in response to these stresses are not fully understood. Here we find that the expression of a WRKY transcription factor WRKY46 is rapidly induced by drought, salt and oxidative stresses. Mutations of WRKY46 by T-DNA insertion lead to more sensitive to drought and salt stress, whereas, overexpression of WRKY46 exhibits hypersensitive in soil culture with higher water loss rate, but increased tolerance on the agar plates. ABA induced stomatal closing is impaired in the WRKY46 overexpressing line (OV46), which is potentially due to the lower ROS accumulation in the guard cells. Real-time qPCR and GUS activity assay further demonstrate that WRKY46 is expressed in guard cells, but its expression is not affected by dehydration treatment, suggesting different regulatory mechanisms for WRKY46 between guard cells and other WRKY46 expressed tissues. The stomatal movement and conductance assay indicate that WRKY46 is involved in light-dependent stomatal opening. Further microarray analysis reveals that WRKY46 regulates a set of genes involved in cellular osmoprotection and redox homeostasis under dehydration stress. Determinations of ROS and MDA content confirm its role in oxidative detoxification under stress. Furthermore, we find that WRKY46 modulates light-dependent starch metabolism in guard cells via regulating QQS gene expression. Taken together, we demonstrate that WRKY46 plays a role in modulating cellular osmoprotection and redox homeostasis under drought and salt stress, and functions independently in stomatal movement via regulating light-dependent starch metabolism and ROS levels in guard cells.

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Ding ZJ, Yan JY, Xu XY, Yu DQ, Li GX, Zhang SQ, Zheng SJ