Functional characterization reveals MiNAC25 and MiSGR1 as key regulators of chlorophyll degradation in mango

Chlorophyll degradation is crucial for fruit ripening and coloration, but its transcriptional regulation in mango (Mangifera indica L.) remains unclear. Here, we investigated two mango cultivars, 'Guire 82' (persistent green) and 'Neelum' (yellowing), and integrated metabolomic and transcriptomic analyses implicated porphyrin and chlorophyll metabolism as the central pathway underlying peel color divergence. Weighted gene co-expression network analysis (WGCNA) identified key modules linked to pigmentation, from which we uncovered that a NAC-family transcription factor MiNAC25 as a central regulator within the chlorophyll degradation network. MiSGR1 a key chlorophyll catabolic gene, showed co-expression with MiNAC25, and in silico analysis revealed potential NAC-binding sites in its promoter. Subcellular localization confirmed the nuclear localization of MiNAC25 and the chloroplast localization of MiSGR1. Functional validation in tomato demonstrated that heterologous overexpression of either MiNAC25 or MiSGR1 significantly accelerated chlorophyll degradation and up-regulated the expression of endogenous chlorophyll catabolic genes (SlPPH, SlPAO, SlRCCR). Notably, MiNAC25 overexpression also activated the tomato SGR ortholog. Our findings reveal a previously uncharacterized transcriptional module in which the nuclear MiNAC25 potentially coordinates chlorophyll breakdown, possibly through influencing MiSGR1 and other catabolic genes, to govern peel yellowing in mango. This study provides key insights into the regulatory mechanism of fruit coloration and identifies MiNAC25 and MiSGR1 as strategic targets for improving mango fruit quality.