Genome-Wide Identification and Functional Characterization of Brown Spot Resistance Genes in Rice (Oryza sativa L.)

Rice brown spot (BS) caused by Cochliobolus miyabeanus affects both rain-fed and upland rice production, causing both yield and grain quality loss. Here, we used a genome-wide association study (GWAS) to analyze the resistance of 130 rice cultivars to BS disease. We identified two quantitative trait loci on chromosome 4. We screened three candidate genes using two kinds of RNA-seq data, LD block, Gene Ontology, Kyoto Encyclopedia of Genes and Genomes databases (KEGG), and reverse transcription-quantitative polymerase chain reaction. To further identify the candidate gene function, we constructed transgenic lines to verify the gene resistance functions against C. miyabeanus. The gene function research about the overexpression lines of OsExo70F3 and OsBSR820 and the Osmed30 gene function loss T-DNA lines showed more resistance to BS than their wildtypes. The exo70 and Med gene families reportedly participate in abiotic stress in rice, and OsBSR820 is a novel functional gene detected in GWAS-based studies. Subcellular localization results also showed that these genes were located in the cellular sites associated with plant immunity. This is the first study to use GWAS to locate BS resistance genes and to identify the function of genes. We believe that this study will provide valuable insights for exploring additional BS disease resistance-related genes in the future.