PbrWRKY70 increases pear (Pyrus bretschneideri Rehd) black spot disease tolerance by negatively regulating ethylene synthesis via PbrERF1B-2

Abstract

Various pear plant cultivars exhibit diverse abilities to resist pear black spot disease (BSD), while the precise molecular mechanisms of resistance against pear BSD remain unclear. This study proposed a profound expression of a WRKY gene, namely PbrWRKY70, derived from Pyrus bretschneideri Rehd, within a BSD-resistant pear cultivar. Comparative analysis against the wild-type revealed that the overexpression of PbrWRKY70 engendered augmented BSD resistance of transgenic Arabidopsis thaliana and pear calli. Notably, the transgenic plants exhibited higher activities of superoxide dismutase and peroxidase, along with an elevated capacity to counteract superoxide anions via increased anti-O2-. Additionally, these plants displayed diminished lesion diameter, as well as reduced levels of hydrogen peroxide, malondialdehyde and 1-aminocyclopropane-1-carboxylic acid (ACC) contents. We subsequently demonstrated that PbrWRKY70 selectively bound to the promoter region of ethylene-responsive transcription factor 1B-2 (PbrERF1B-2), a potential negative regulator of ACC, thereby downregulating the expression of ACC synthase gene (PbrACS3). Consequently, we confirmed that PbrWRKY70 could enhance pear resistance against BSD by reducing ethylene production via modulation of the PbrERF1B-2-PbrACS3 pathway. This study established the pivotal relationship among PbrWRKY70, ethylene synthesis and pear BSD resistance, fostering the development of novel BSD-resistant cultivars. Furthermore, this breakthrough holds the potential to enhance pear fruit yield and optimize storage and processing during the later stages of fruit maturation.