Higher carbon reserves are associated with delayed leaf senescence and attenuated starvation responses in Brassica...

Leaf senescence is a complex developmental process influenced by environmental cues and internal metabolic status. However, the extent to which carbon availability contributes to variation in senescence progression remains incompletely understood. Here, we describe a Brassica rapa line, DLS-177, that exhibits delayed senescence under multiple conditions, including prolonged darkness, nitrogen deficiency, and developmental aging. Compared with the control line DLS-042, DLS-177 displayed higher basal levels of glucose and total soluble sugars (glucose + fructose) and slower depletion during dark treatment. These differences were accompanied by reduced induction of carbon starvation-associated marker genes, including BrbZIP63, BrDIN1, and BrDIN6. Transcriptome analysis indicated that genotype-dependent differences were selective rather than global, with reduced expression of key senescence-associated regulators, including ORE1 and NAC transcription factors, and relative maintenance of chloroplast-related gene expression. DLS-177 also displayed reduced sensitivity to senescence-promoting treatments, including methyl jasmonate and TOR inhibition. Exogenous sucrose partially alleviated methyl jasmonate-induced senescence in the control line but had limited additional effects in DLS-177. Together, these results indicate that differences in carbon status and depletion dynamics are associated with altered responsiveness of senescence-associated transcriptional programs. Rather than defining a single regulatory pathway, our findings suggest that metabolic status contributes to variation in the timing and progression of leaf senescence under stress conditions.