Abstract

Flowering Chinese cabbage is highly susceptible to postharvest quality loss, including water loss, yellowing, and nutrient degradation. Sucrose acts as both essential quality indicators and signaling molecules. Although RAV transcription factors are known regulators of plant development and stress responses, the molecular mechanism through which RAV transcription factors regulate leaf senescence via sucrose biosynthesis remains unclear. Herein, we systematically analyzed the expression of 12 sucrose biosynthesis-related genes (7 BrSUSs and 5 BrSPSs ), and 14 BrRAVs after 5 days of dark-induced leaf senescence at 23 °C and 70% relative humidity in flowering Chinese cabbage. Notably, after 5 days of dark-induced leaf senescence, the expression of BrSUS1 , BrSPS1 , and BrSPS4 decreased, whereas BrRAV8 expression increased. Overexpression of BrRAV8 in flowering Chinese cabbage promoted leaf senescence, accompanied by reduced chlorophyll content, decreased levels of soluble sugar and sucrose, and downregulation of BrSUS1 , BrSPS1 , and BrSPS4 . Concurrently, chlorophyll degradation-related genes ( BrNYC1 and BrNYE1 ) and the senescence marker gene ( BrSAG12 ) were upregulated. In contrast, silencing of BrRAV8 delayed senescence, increased chlorophyll and sucrose contents, and reduced the expressions of senescence-associated genes ( BrNYC1 , BrNYE , and BrSAG12 ). Furthermore, silencing of BrSUS1 , BrSPS1 , or BrSPS4 accelerated leaf senescence, characterized by reduced chlorophyll content, elevated expression of BrNYC1 , BrNYE1 , and BrSAG12 , and a decline in soluble sugar and sucrose contents. Using yeast one-hybrid, electrophoretic mobility shift, and dual luciferase assays, we verified that BrRAV8 directly binds to the promoters of BrSUS1 , BrSPS1 , and BrSPS4 and suppresses their expression. These results demonstrate that BrSUS1 , BrSPS1 , and BrSPS4 negatively regulate leaf senescence, whereas BrRAV8 functions as a positive r