ORYZA SATIVA SPOTTED-LEAF 41 (OsSPL41) Negatively Regulates Plant Immunity in Rice

Identification of immunity-associated leucine-rich repeat receptor-like protein kinases (LRR-RLK) is critical to elucidate the LRR-RLK mediated mechanism of plant immunity. Here, we reported the map-based cloning of a novel rice SPOTTED-LEAF 41 (OsSPL41) encoding a putative LRR-RLK protein (OsLRR-RLK41/OsSPL41) that regulated disease responses to the bacterial blight pathogen Xanthomonas oryzae pv. oryzae (Xoo). An 8-bp insertion at position 865 bp in a mutant spotted-leaf 41 (spl41) allele led to the formation of purple-brown lesions on leaves. Functional complementation by the wild type allele (OsSPL41) can rescue the mutant phenotype, and the complementary lines showed similar performance to wild type in a number of agronomic, physiological and molecular indices. OsSPL41 was constitutively expressed in all tissues tested, and OsSPL41 contains a typical transmembrane domain critical for its localization to the cell membrane. The mutant exhibited an enhanced level of resistance to Xoo in companion of markedly up-regulated expression of pathogenesis-related genes such as OsPR10a, OsPAL1 and OsNPR1, while the level of salicylic acid was significantly increased in spl41. In contrast, the over-expression lines exhibited a reduced level of H₂O₂ and were much susceptible to Xoo with down-regulated expression of pathogenesis-related genes. These results suggested that OsSPL41 might negatively regulate plant immunity through the salicylic acid signaling pathway in rice.