Arabidopsis transcription factor WRKY 8 functions antagonistically with its interacting partner VQ 9 to modulate salinity stress tolerance

Abstract

Summary: The WRKY transcription factors have been demonstrated to play crucial roles in regulating stress responses; however, the exact mechanisms underlying their involvement in stress responses are not fully understood. A rabidopsis WRKY8 was predominantly expressed in roots and was highly upregulated by salt treatment. Disruption of WRKY 8 rendered plants hypersensitive to salt, showing delayed germination, inhibited post‐germination development and accelerated chlorosis. Further investigation revealed that WRKY 8 interacted with VQ 9, and their interaction decreased the DNA‐binding activity of WRKY 8. The VQ 9 protein was exclusively localized in the nucleus, and VQ9 expression was strongly responsive to N a Cl treatment. Mutation of VQ9 enhanced tolerance to salt stress, indicating that VQ 9 acts antagonistically with WRKY 8 to mediate responses to salt stress. The antagonist functions of WRKY 8 and VQ 9 were consistent with an increased or reduced N a+/K+ concentration ratio, as well as contrasting expression patterns of downstream stress‐responsive genes in salt‐stressed wrky8 and vq9 mutants. Moreover, chromatin immunoprecipitation (C h IP) assays showed that WRKY 8 directly bound the promoter of RD29A under salt conditions. These results provided strong evidence that the VQ 9 protein acts as a repressor of the WRKY 8 factor to maintain an appropriate balance of WRKY 8‐mediated signaling pathways to establish salinity stress tolerance.