OsMbl1 Counteracts OsGdsl1-Mediated Rice Blast Susceptibility by Inhibiting Its Lipase Activity.

Plant lectins have a significant impact on the defense against pathogens and insect attacks. The jacalin-related lectin OsMbl1 from rice (Oryza sativa L.) has been reported to play a crucial role in pattern-triggered immunity (PTI). However, the underlying mechanism remains unclear. In this study, we identified a GDSL-like lipase, OsGdsl1, that interacts with OsMbl1 both in vitro and in vivo. The OsGdsl1 protein, which has lipase activity, is localized in the lipid bodies and apoplast. The expression of OsGDSL1 is modulated upon exposure to Magnaporthe oryzae (M. oryzae) or plant hormones. Deletion of the OsGDSL1 gene not only improved the resistance of rice to M. oryzae, but also led to an increased ROS burst after chitin treatments. The expression of some pathogenesis-related (PR) genes was upregulated in the mutants. We also found that OsMbl1 inhibited the lipase activity of OsGdsl1 during infection with M. oryzae. Overall, our results suggest that OsGdsl1 negatively regulates rice immunity to M. oryzae infection by downregulating ROS bursts and PR gene expressions, while its lipase activity, which is inhibited by OsMbl1, contributes to the enhancement of rice innate immunity during M. oryzae infection.