BoLrgB promotes programmed cell death of postharvest broccoli through regulating antioxidant pathways under oxidative stress

Programmed cell death (PCD) was the primary cause of broccoli senescence, and LrgB had been reported that played a significant role in the process of PCD in plants. But there was no report on the function of broccoli LrgB gene in PCD under oxidative stress. In this study, it was found that 80 µM melatonin could significantly delay chlorophyll degradation and cell apoptosis of post-harvest broccoli, while inhibit the expression of the BoLrgB . For further investigate the role of BoLrgB in PCD, we overexpressed BoLrgB in Arabidopsis . The results showed that overexpression of BoLrgB reduced the activity of ascorbate peroxidase (APX), superoxide dismutase (SOD) and catalase (CAT) in Arabidopsis and increased the contents of superoxide Radical (O 2 - ), hydrogen peroxide (H 2 O 2 ), malondialdehyde (MDA) under oxidative stress. Meanwhile, overexpression of BoLrgB induced the expression of pro-apoptotic genes ( Atmetacaspase1 , Atmetacaspase3 ) and chlorophyll catabolism genes ( AtPPH , AtSGR1 , AtPAO , AtCHL ), as well as inhibited the expression of anti-apoptotic genes ( AtBI1 , AtDAD1 , AtFtSH1 ). In addition, BoLrgB interacted with BoAPX and BoMDHAR in chloroplasts, which may interfere the expression levels of BoAPX and BoMDHAR , and promote the generation of ROS. In conclusion, the BoLrgB reduced the antioxidant and anti-apoptotic levels in Arabidopsis under oxidative stress, as well as interacted with BoAPX and BoMDHAR which were involved in the regulation of the PCD process in broccoli. • Melatonin proved to delay yellowing and senescence of broccoli. • The antioxidant and PCD regulatory functions of BoLrgB were uncovered . • BoLrgB interacts with BoAPX/BoMDHAR to regulate PCD in broccoli.