SGR mutation in pak choi prolongs its shelf life by retarding chlorophyll degradation and maintaining membrane function

Abstract

Leaf yellowing has become an important limiting factor for harvested pak choi, affecting its commodity quality and market value. Our previous results showed that in stay-green pak choi, nye, an SGR mutant likely prolongs its shelf life. To uncover the mechanism of the SGR mutation underlying extended shelf life, nye and its near isogenic line (nye-) harboring the SGR allele were used to conduct the postharvest analysis. Compared with nye-, nye exhibited delayed leaf yellowing and weight loss, prolonged shelf life, and maintained high –a* value and Fv/Fm during shelf life. High chlorophyll content and integral membrane structure were observed in nye, which likely contributed to delayed postharvest yellowing. The membrane integrity of nye was well maintained, manifested as a low level of electrolyte leakage and malondialdehyde (MDA). The increased accumulation of phospholipids and glycolipids, high degree of fatty acid unsaturation, and downregulated activities and gene expression of lipoxygenase （LOX）and phospholipase D （PLD）proved that less severe membrane lipid metabolism occurred in nye. These factors may be the key to delaying postharvest yellowing and extending shelf life. Our findings will contribute to the development of a new method to delay postharvest yellowing and maintain the shelf life and commercial value of leafy vegetables by using the SGR gene.