SA and PTI Signaling Involve in the Positive Regulation of Receptor‐Like Protein PbeRLP3 to Valsa Canker Resistance in Pyrus betulifolia

Valsa canker, a disease caused by necrotrophic fungi belonging to the genus Valsa, ranks among the most destructive pathogens jeopardizing the sustainable development of the pear and apple industries. The identification of resistance-related genes is therefore of great significance for advancing resistance breeding efforts and formulating effective disease control strategies. Receptor-like proteins (RLPs) are crucial membrane-localized sensors that play significant roles in diverse plant immunological processes. Still, the regulatory roles of RLPs in the Valsa canker resistance remain elusive. In this study, we found that a leucine-rich repeat receptor-like protein (LRR-RLP) gene, PbeRLP3, was highly induced by Valsa pyri in 'Duli-G03' (Pyrus betulifolia, a rootstock of pear) suspension cells. Overexpression of PbeRLP3 in 'Huangguan' pear (P. bretschneideri), 'Fuji' apple (Malus domestica) fruits, and 'Duli-G03' suspension cells significantly improved resistance to Valsa canker. However, the resistance contributed by PbeRLP3 was largely compromised by removing its Transmembrane (TM) region. RNA-seq and qRT-PCR analyses demonstrated that the expression of multiple genes associated with salicylic acid (SA), pattern-triggered immunity (PTI), and abscisic acid (ABA) pathways were induced in PbeRLP3-OE cells. Furthermore, Weighted Gene Co-Expression Network Analysis (WGCNA) displays that PbeRLP3 is co-expressed with 3 RLP genes and 17 Receptor-like kinase genes (RLKs). The results presented herein provide fresh insights into the effective screening of RLP genes related to resistance using specific molecular approaches, along with their application in follow-up molecular breeding strategies for boosting plant resistance.