The ethylene-mediated transcription factors PuERF13/PuDof2.5 and DNA demethylases PuDML2 promote ester biosynthesis in cold-stored 'Nanguo' pear

Abstract

Aroma is the main sensory quality index of 'Nanguo' (Pyrus ussuriensis Maxim.), with esters being the predominant contributors. The 'Nanguo' pear exhibits extended shelf life when stored under refrigeration; however, the concentration of esters diminishes progressively over time. Our previous studies have demonstrated that PuERF13 and PuDof2.5 regulated PuAAT1 transcription in response to ethylene treatment, thereby promoting ester biosynthesis in 'Nanguo' pear under cold storage conditions. However, the underlying mechanisms remain to be elucidated. In this study, we found that PuDof2.5 activates PuERF13 transcription by binding to its promoter, whereas PuERF13 does not bind to the PuDof2.5 promoter nor regulate its transcription in vitro. Additionally ethylene treatment up-regulated the expression of a DNA repair enzyme gene, PuMAG1. PuMAG1 was found to bind to the PuDof2.5 promoter but not to the PuAAT1 promoter. Conversely, PuERF13 bound to the PuMAG1 promoter and subsequently induced its transcription. Notably, the methylation levels of the PuDof2.5 and PuAAT1 promoters were lower in fruit treated with ethylene compared to the control fruit. Additionally, the expression of the DNA demethylase PuDML2 was significantly higher in ethylene treated fruit, and an interaction between PuERF13 and PuDML2 was identified. These findings reveal a novel molecular mechanism by which ethylene promotes ester production in 'Nanguo' pear during cold storage.