Genome-wide transcriptional response of papain-like cysteine protease-mediated resistance against Xanthomonas oryzae pv. oryzae in rice.

KEY MESSAGE: Transgenic rice overexpressing PLCP attenuated the virulence of Xanthomonas oryzae pv. oryzae through extensive activation of transduction signal and transcription activities that orchestrate downstream responses including the biosynthesis of secondary metabolites and up-regulation of several pathogenesis-related proteins. High-throughput transcriptome investigations of plant immunity highlight the complexity of gene networks leading to incompatible interaction with the pathogen. Accumulating findings implicate papain-like cysteine proteases (PLCPs) as a central hub in plant defense. While diverse roles of PLCPs in different pathosystems have become more evident, information on gene networks and signaling pathways necessary to orchestrate downstream responses are lacking. To understand the biological significance of cysteine protease against Xanthomonas oryzae pv. oryzae, PLCP overexpression and knockout rice lines were generated. The pathogenicity test revealed the attenuation of Xanthomonas oryzae pv. oryzae race K3a virulence in transgenic lines which is ascribed to high hydrogen peroxide and free salicylic acid accumulation. Next-generation sequencing of RNA from transgenic and wild-type plants identified 1597 combined differentially expressed genes, 1269 of which were exclusively regulated in the transgenic libraries. It was found that PLCP aids rice to circumvent infection through the extensive activation of transduction signal and transcription factors that orchestrate downstream responses, including up-regulation of multiple pathogenesis-related proteins and biosynthesis of secondary metabolites.