ABA-induced PbrMYB8-PbrMYB169 module promotes lignin biosynthesis in corking disorder in pear fruit

Abstract

Pear fruit corking disorder is a non-infectious physiological condition that primarily occurs during the late developmental stages of pear and significantly impacts fruit quality and economic value in several major cultivars. As the underlying mechanism remains unclear, effective prevention strategies and genetic improvements continue to present major challenges. In this study, ‘Akizuki’ pear was used as experimental material, and the lignin content in cork-affected tissue was found to be significantly higher than in healthy tissue. Exogenous abscisic acid (ABA) treatment induced cork formation and promoted lignin biosynthesis, a major structural component, in both pear fruits and calli. Through integrated RNA-seq and expression analyses, we identified the ABA-responsive gene PbrMYB8, which was differentially expressed between healthy and diseased tissues and associated with lignin biosynthesis during corking disorder. Stable transformation of PbrMYB8 into pear calli and Arabidopsis confirmed its role in promoting lignin biosynthesis. Notably, PbrMYB8 not only activated lignin biosynthesis genes independently but also interacted with PbrMYB169 to form a protein complex that co-regulated their expression. These findings improve our understanding of lignin biosynthesis in pear fruit corking disorder by identifying a key regulator and its interaction network and provide a theoretical foundation for future strategies aimed at improving pear fruit quality.