Understanding rice responses to the combination of Bacterial Panicle Blight and High Nighttime temperatures

To dissect the genetic basis of these differential responses, we used RNA-sequencing for comparative transcriptional profiling on two selected temperature-independent accessions with contrasting resistance (R) and susceptible (S) responses. Comparisons among accessions (R and S), treatments: Mock (M) and pathogen (P) and temperatures: NNT and HNT resulted in 6,346 differentially expressed genes (DEGs). Weighted gene co-expression network analysis of DEGs uncovered three modules showing contrasting expression patterns between the resistant and the susceptible accessions and MAPMAN analysis further identified 86 genes related to biotic stress.

Those 86 genes were mapped to multiple functional categories and were evenly divided into upregulated in the resistant accession or upregulated in the susceptible accession after single stress (HNT or P) and combined stresses (HNT and P). We found enrichment in several functional categories including proteolysis, defense signaling, secondary metabolism and hormone regulation highlighting a complex transcriptional reprogramming involving multiple pathways.

The results highlight the complex transcriptional reprogramming underlying stress responses and revealed that the genes responding to either HNT or P or the combination HNT/P are the same responses operating metabolism, proteolysis and secondary metabolites. The results from this research will enable deeper understanding of rice differential responses to BPB when combined with high night temperatures while providing key candidate genes to develop rice varieties resilient to the combination biotic and abiotic stresses such as BPB and HNT.