Leaf senescence is a major contributor to postharvest quality deterioration, and postharvest losses of leafy vegetables in China are substantial. Therefore, elucidating the underlying regulatory mechanisms is critical for reducing these losses. This study has shown that red light-emitting diode (RL) treatment can effectively delay postharvest senescence in pak choi leaves. Transcriptome sequencing revealed that RL mainly modulates the expression of genes involved in plant hormone signaling pathways. Further analysis confirmed that RL treatment significantly suppresses auxin (IAA) degradation in postharvest pak choi. Notably, the senescence-associated NAC transcription factor (TF), BrNAC075, was identified as a key regulator in RL-mediated leaf senescence of pak choi. Overexpression of BrNAC075 in Arabidopsis and pak choi was found to accelerate leaf senescence and to attenuate the senescence-delaying effect of RL. Conversely, silencing of BrNAC075 expression in pak choi was observed to delay leaf senescence. Mechanistically, BrNAC075 was shown to bind directly to the promoters of the IAA-responsive gene BrSAUR70 and the chlorophyll (Chl) catabolic gene BrSGR2, thereby transcriptionally activating these target genes. As such, endogenous IAA and Chl levels were reduced, and leaf senescence was accelerated. These findings provide new mechanistic insight into RL-regulated leaf senescence via BrNAC075 and indicate promising molecular targets for the development of technologies aimed at improving leafy vegetable quality and storage resistance.
Chen et al. (Wed,) studied this question.