Inhibition of rice OsOLP1 by Magnaporthe oryzae effector MoHrip2 suppresses plant resistance and promotes pathogen infection

• The apoplast-localized osmotin-like protein OsOLP1 interacts with the Magnaporthe oryzae effector MoHrip2 both in vivo and in vitro . • OsOLP1 responds to M. oryzae infection and contributes to rice resistance against M. oryzae through multiple disease resistance pathways. • M. oryzae effector MoHrip2 is considered to be an inhibitor of OsOLP1, a PR5 protein, thereby promoting infection. Rice blast, caused by Magnaporthe oryzae , is a devastating fungal disease that severely impairs rice growth and development, posing a significant threat to global food security. MoHrip2 is a secretory protein isolated from the culture broth of M. oryzae . This protein not only acts as an elicitor to induce plant resistance but also plays the role of a virulence factor, promoting the infection and colonization of M. oryzae . However, MoHrip2 recognition and regulation by host resistance during the rice- M. oryzae interaction remains unclear. This study identified that an apoplast-localized osmotin-like protein, OsOLP1, from rice, interacts with MoHrip2 in vivo and in vitro , as validated by yeast two-hybrid, GST pull-down and luciferase complementation assays, with peaked expression levels during M. oryzae infection stage, indicating that OsOLP1 can respond to the infection. Moreover, the pathogenicity of M. oryzae was enhanced in OsOLP1 knockout lines, but suppressed in the overexpression lines, suggesting that OsOLP1 positively regulates resistance to rice blast disease. The expression level of disease resistance-related marker genes also significantly increased in the overexpression lines, indicating that OsOLP1 contributes to rice resistance via multiple defense signaling pathways. Furthermore, in vitro inoculation tests showed that MoHrip2 could attenuate OsOLP1-mediated resistance to rice blast. This study underscores that M. oryzae effector MoHrip2 targets rice OsOLP1, weakening resistance to M. oryzae and enhancing pathogen virulence.