Histone H3K36 Methyltransferase MaSET40 Regulates Cold Tolerance in Banana Fruit

Histone methylation is an important epigenetic mechanism that regulates plant development and stress responses, but its role in postharvest fruit chilling injury remains unknown. Here, we identified a cold-inducible SET domain protein, MaSET40, in banana (Musa acuminata) and found that it functions as a trimethylation of histone H3 lysine 36 (H3K36me3) methyltransferase. Transient overexpression of MaSET40 in banana fruit peel accelerated chilling injury, whereas virus-induced silencing of MaSET40 alleviated cold-induced peel damage. Transcriptome profiling revealed that MaSET40 activates genes involved in reactive oxygen species (ROS) accumulation and membrane lipid degradation, including MaPPO1, MaPPO3, MaRBOHB, Malipase, MaPLA2, and MaLOX3.1. Chromatin immunoprecipitation followed by quantitative PCR (ChIP-qPCR) further showed that MaSET40 increased H3K36me3 enrichment at these gene loci, accompanied by higher transcript levels. These results reveal an H3K36me3-mediated epigenetic mechanism that promotes chilling injury in postharvest banana fruit and identify MaSET40 as a potential target for improving cold tolerance in tropical fruits.