Jacalin-Related Lectin OsJacLK1 Positively Regulates Resistance to Magnaporthe oryzae in Rice

Jacalin-related lectins play crucial roles in plant adaptation to abiotic and biotic stresses. The rice genome encodes four putative jacalin-related lectin kinase genes (OsJacLKs), but their functions toward environmental stresses remain largely uncharacterized. This study demonstrates that a putative jacalin-related lectin kinase, OsJacLK1, conferred resistance to the rice blast fungus Magnaporthe oryzae rather than salt stress. OsJacLK1 protein exhibited agglutination activities and affinity toward chitin, fungal cell wall, and mannose. OsJacLK1 was transcriptionally activated by stress-related phytohormones salicylic acid (SA), methyl jasmonate (MeJA), abscisic acid (ABA), and indoleacetic acid (IAA), as well as salinity, chitin, and M. oryzae inoculation, suggesting its involvement in broad stress-responsive signaling pathways. Overexpression of OsJacLK1 in rice led to reduced susceptibility to rice blast disease, whereas loss-of-function osjaclk1 lines showed no significant phenotypic difference from wild-type plants upon infection. Enhanced resistance in OsJacLK1-overexpressing lines was associated with a stronger reactive oxygen species (ROS) burst and elevated hydrogen peroxide accumulation, accompanied by the up-regulation of defense-related genes (OsRac1, OsSGT1, OsMAPK6, OsPAL1, OsNAC4, OsPBZ1, OsAOS2, and OsJAZ8). Collectively, our findings establish that OsJacLK1 acts as a positive regulator of rice immunity against M. oryzae, modulating the cellular redox state, highlighting its potential as a candidate for genetic improvement of disease resistance in rice.