Endo-1,4-beta-xylanase 1 (MoXYL1) secreted by Magnaporthe oryzae triggers defense responses and induces cell death in rice

The rice blast fungus Magnaporthe oryzae devastates cultivated rice (Oryza sativa L.), causing extensive crop losses. Despite being a major pathogen, information on this pathosystem, especially on the proteins associated with fungal pathogenicity and host defense response, is relatively scarce. Utilizing liquid chromatography-mass spectrometry (LC-MS/MS), we identified 123 in planta-secreted M. oryzae proteins in rice leaves and screened for their cell death-inducing activity. Biochemical characterization of these M. oryzae proteins revealed an endo-1,4-beta-xylanase (MoXYL1), which induces cell death in Nicotiana benthamiana leaves and H2O2 accumulation in rice suspension-cultured cells. Transgenic rice plants (P-DUF26::MoXYL1) expressing MoXYL1 driven by rice DOMAIN OF UNKNOWN FUNCTION PROTEIN 26 (DUF26) promoter enhanced expression of pathogen-responsive and hormone-related genes, and resistance to the M. oryzae and Cochliobolus miyabeanus. Data-independent acquisition (DIA) MS-based proteomics of wild-type and PDUF26::MoXYL1 rice revealed 1,833 significantly modulated rice proteins upon M. oryzae infection. Among these, 219 proteins showed a significant increased abundance exclusively in PDUF26::MoXYL1 transgenic rice, while 410 proteins showed increased abundance in both wild-type and PDUF26::MoXYL1. Notably, xylanase inhibitor proteins, pathogenesis-related proteins, and other proteins associated with jasmonic acid biosynthesis exhibited increased abundance in response to M. oryzae. Based on these results, we proposed a putative signaling network induced by MoXYL1 and M. oryzae. In summary, our findings highlight the crucial role of MoXYL1 in inducing rice defense and in potentially enhancing rice disease resistance against fungal pathogens.