Transcriptomic and Metabolomic Analyses of the Piz-t-Mediated Resistance in Rice against Magnaporthe oryzae

Magnaporthe oryzae causes devastating rice blast disease, significantly impacting rice production in many countries. Among the many known resistance (R) genes, Piz-t confers broad-spectrum resistance to M. oryzae isolates and encodes a nucleotide-binding site leucine-rich repeat receptor (NLR). Although Piz-t-interacting proteins and those in the signal transduction pathway have been identified over the last decade, the Piz-t-mediated resistance has not been fully understood at the transcriptomic and metabolomic levels. In this study, we performed transcriptomic and metabolomic analyses in the Piz-t plants after inoculation with M. oryzae. The transcriptomic analysis identified a total of 15,571 differentially expressed genes (DEGs) from infected Piz-t and wild-type plants, with 2791 being Piz-t-specific. K-means clustering, GO term analysis, and KEGG enrichment pathway analyses of the total DEGs identified five groups of DEGs with distinct gene expression patterns at different time points post inoculation. GO term analysis of the 2791 Piz-t-specific DEGs revealed that pathways related to DNA organization, gene expression regulation, and cell division were highly enriched in the group, especially at early infection stages. The gene expression patterns in the transcriptomic datasets were well correlated with the metabolomic profiling. Broad-spectrum "pathway-level" metabolomic analyses indicated that terpenoid, phenylpropanoid, flavonoid, fatty acid, amino acid, glycolysis/TCA, and phenylalanine pathways were altered in the Piz-t plants after M. oryzae infection. This study offers new insights into the molecular dynamics of transcripts and metabolites in R-gene-mediated resistance against M. oryzae and provides candidates for enhancing rice blast resistance through the engineering of metabolic pathways.