Transcriptional reprogramming regulated by the antagonistic crosstalk between strigolactone and sugar during leaf senescence of chrysanthemum (Chrysanthemum morifolium)

Strigolactone (SL), a novel plant hormone, plays a vital role in promoting leaf senescence. Sugar, a nutrient source widely used to retain freshness of cut flowers, was recently reported to alleviate SL-induced leaf senescence; however, the underlying molecular mechanisms remain unclear. Leaf senescence during transportation and storage of cut chrysanthemum considerably affects its shelf life and ornamental value. In this study, we found that sucrose antagonizes SL-induced leaf senescence in chrysanthemum. Transcriptional reprogramming analysis revealed a number of differentially expressed genes antagonistically regulated by SL and sucrose, mainly including those related to SL signaling, sugar signaling, ethylene, auxin, jasmonic acid, reactive oxygen species, chlorophyll metabolism pathways, and transcription factors (such as WRKY, NAC, AP2/ERF, and MYB). Virusbased transient silencing of CmWRKY6-Like in chrysanthemum revealed that CmWRKY6-Like positively regulates leaf senescence and involves the antagonistic regulation of leaf senescence by SL and sucrose. This study provides a basis for understanding the molecular mechanisms underlying the antagonistic roles of SL- and sugarmediated leaf senescence in chrysanthemum.