PbrChiA: a key chitinase of pear in response to infection by interacting with PbrLYK1b2 and down-regulating ROS accumulation.

Pear ring rot, caused by the pathogenic fungi , seriously affects pear production. While the infection-induced reactive oxygen species (ROS) burst of infected plants limits the proliferation of during the early infection stage, high ROS levels can also contribute to their growth during the later necrotrophic infection stage. Therefore, it is important to understand how plants balance ROS levels and resistance to pathogenic during the later stage. In this study, we identified , a glycosyl hydrolases 18 (GH18) chitinase-encoding gene with high infection-induced expression, through a comparative transcriptome analysis. Artificial substitution, stable overexpression, and virus induced gene silencing (VIGS) experiments demonstrated that PbrChiA can positively regulate pear resistance as a secreted chitinase to break down mycelium and that overexpression of suppressed infection-induced ROS accumulation. Further analysis revealed that PbrChiA can bind to the ectodomain of PbrLYK1b2, and this interaction suppressed PbrLYK1b2-mediated chitin-induced ROS accumulation. Collectively, we propose that the combination of higher antifungal activity from abundant PbrChiA and lower ROS levels during later necrotrophic infection stage confer resistance of pear against .