Inducer of CBF Expression1 (ICE1) Interacts With WRKY46 to Modulate Salicylic Acid‐Induced Leaf Senescence in Arabidopsis

Leaf senescence is triggered by various endogenous signals and exogenous cues. The plant hormone salicylic acid (SA) is a key signaling molecule that induces leaf senescence, but the underlying mechanism has not been fully clarified. Here, we found that INDUCER OF CBF EXPRESSION1 (ICE1) negatively regulates SA-induced leaf senescence in Arabidopsis. Upon treatment with SA, the ice1-2 mutant displayed an accelerated-leaf senescence phenotype compared with that of the wild type (Col-0), including severe leaf yellowing, lower chlorophyll content, and higher expression levels of senescence-associated genes, whereas ICE1-overexpressing plants exhibited delayed leaf senescence. ICE1 interacts with WRKY46, a positive regulator of SA-induced leaf senescence, to suppress its ability to activate WRKY6 expression. Phenotypic assays indicated that the accelerated-leaf senescence of ice1-2 was largely recovered by wrky46, indicating that ICE1 functions genetically upstream of WRKY46 during SA-induced leaf senescence. Further analyses suggested that the accelerated-leaf senescence phenotype of ice1-2 is dependent on WRKY6. Collectively, our results demonstrate the negative regulatory role of ICE1 in SA-induced leaf senescence. Given the importance of SA in leaf senescence, the discovery of the role of ICE1 reveals new details of how the onset of senescence is regulated.