P-081 - Transcriptome profiling and co-expression network analysis of rice leaf responses to Cercospora janseana

Cercospora janseana is a re-emerging fungal pathogen that causes narrow brown leaf spot (NBLS) and threatens global rice production. Elucidating the molecular basis of NBLS resistance is crucial for developing durable cultivars, however, these mechanisms are currently unknown. This study examined gene expression during C. janseana infection of rice leaves using RNAseq. Tissue was collected from inoculated and non-inoculated resistant (LaGrue) and susceptible (Cypress) varieties at 1, 7, 13, and 19 days post-inoculation (dpi). Cypress exhibited few differentially expressed genes (DEGs) at early timepoints but peaked at 13 dpi with 4,731 DEGs, while LaGrue showed an earlier and stronger response at 7 dpi (1,337 upregulated DEGs). This pattern suggests that the resistance response in LaGrue was triggered prior to 7 dpi and that the pathogen remained largely undetected before transitioning into necrotrophy between 7 and 13 dpi in Cypress. GO enrichment analyses identified an enrichment of extracellular recognition genes in LaGrue at 1 and 7 dpi. Conversely, immune suppression was detected at 13 dpi in Cypress, followed by a transition into cell-death related pathways favoring susceptibility. Weighted gene co-expression network analysis identified 18 co-expression modules with six relevant modules based on expression patterns. These findings highlight temporal and varietal differences in gene regulation, offering valuable insights for enhancing NBLS resistance in rice.