The Arabidopsis thaliana METACASPASE IIf Regulates Sugar Metabolism and Delays Dark-Induced Leaf Senescence

The Arabidopsis thaliana METACASPASE IIf (AtMCA-IIf) is expressed during both developmental cell death and leaf senescence in Arabidopsis thaliana. It has been shown to contribute to developmental cell death but its role in regulating leaf senescence has remained unclear. To investigate this, we conducted dark-induced senescence assays using atmca-IIf mutant lines, which exhibited an accelerated senescence phenotype accompanied by increased levels of glycolytic sugars in light and slow degradation of starch in dark-incubated leaves. Our findings therefore support AtMCA-IIf function in leaf senescence through modulation of sugar metabolism. We propose, on the basis of both in vitro and in vivo data, that one of the proteolytic targets of AtMCA-IIf in this process is PFP_β1, a subunit of the pyrophosphate-dependent fructose-6-phosphate phosphotransferase _β1 (PFP_β1), a key enzyme in the glycolytic pathway. Accordingly, pfp_β1 mutants displayed accelerated senescence of dark-incubated leaves. Together, our results suggest that AtMCA-IIf mitigates leaf senescence through targeted modulation of sugar metabolism, thereby delaying the progression of senescence under dark conditions.