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.