The group IId WRKY transcription factors phosphorylated by mitogen-activated protein kinase 6 negatively regulate leaf senescence in Arabidopsis

Leaf senescence is a tightly regulated developmental process essential for nutrient remobilization and plant fitness. Although some of the WRKY transcription factors are well established as key regulators of senescence, the mechanism of specific WRKY subfamilies remain poorly defined. Here, we show that group IId WRKY transcription factors function as central repressors of leaf senescence in Arabidopsis thaliana. The expression of multiple group IId WRKY genes declines during natural or dark-induced senescence, and a quintuple wrky11/15/17/21/39 mutant exhibits precocious senescence, accelerated chlorophyll degradation, and reduced photosynthetic efficiency. Transcriptome analyses reveal widespread upregulation of senescence-associated genes in the mutant. Integrative RNA-seq and ChIP-seq analyses identify group IId WRKY transcription factors as the direct repressor of WRKY22, a positive regulator of senescence, and genetic disruption of WRKY22 suppresses the early-senescence phenotype. Mechanistically, WRKY11, a representative member of this group, interacts with MPK6 and is phosphorylated at Ser-262, leading to reduced protein stability and diminished transcriptional repression. Together, these findings uncover a MPK-WRKY regulatory module that integrates signaling cascades with transcriptional control to fine-tune the timing of leaf senescence.