Understanding Rice Responses to the Combination of Bacterial Panicle Blight and High Night Temperatures

The disease Bacterial Panicle Blight (BPB) caused by the bacterium Burkholderia glumae is one of the major constraints of global rice production and has been more prevalent in years experiencing unusually high night temperatures (HNT). These observations suggest that BPB could become more devastating in the future with the increase in global temperatures. To initially understand the interplay between BPB and HNT, we compared the phenotypic responses of 20 rice accessions after B. glumae inoculation at two night temperatures: normal night temperature (22 °C) or high night temperature (28 °C). The results revealed temperature-dependent and temperature-independent responses ranging from enhanced susceptibility to moderate resistance. To dissect the genetic basis of these differential responses, we used comparative transcriptomics on two selected temperature-independent accessions with contrasting responses. Comparisons within and between accessions resulted in 6346 differentially expressed genes (DEGs). Weighted gene co-expression network analysis followed by functional characterization, identified 146 genes related to biotic and abiotic stress responses and mapped to several functional categories such as proteolysis, defense signaling, transcription factors, secondary metabolism and hormone regulation. Interestingly, in response to single stress (BPB or HNT) or combined stresses (BPB and HNT), those genes have equivalent pattern of gene expression in each accession. The results from this work unraveled the complexity of rice responses to BPB when combined with HNT, uncovering candidate genes responding to this combination of stresses, which could be further utilized to develop multiple stress resilient rice varieties.