Unraveling the role of effector proteins in Bipolaris oryzae infecting North East Indian rice cultivars through time-course transcriptomics analysis

Bipolaris oryzae, causing brown spot disease in rice, is one of the neglected diseases reducing rice productivity. Limited knowledge is available on the genetics of host-pathogen interaction. Here, we used time-course transcriptome sequencing to elucidate the differential transcriptional responses of the pathogen genes in two contradictory infection-responsive rice hosts. Evaluation of transcriptome data showed similar regulation of fungal genes within susceptible (1733) and resistant (1846) hosts at an early stage however, in the later stage, the number was significantly higher in susceptible (2877) compared to resistant (1955) hosts. GO enrichment terms for upregulated genes showed a similar pattern in both the hosts at an early stage, but in the later stage terms related to degradation of carbohydrates, carbohydrate transport, and pathogenesis are enriched extensively within the susceptible host. Likewise, similar expression responses were observed with the secretory and effector proteins. Plant pathogenic homologs genes such as those involved in appressorium and conidia formation, host cell wall degradative enzymes, etc. were reported to be highly upregulated within the susceptible host. This study predicts the successful establishment of B. oryzae BO1 in both the host surfaces at an early stage, while disease progression only occurs in the susceptible host in later stage. & COPY; 2023 British Mycological Society. Published by Elsevier Ltd. All rights reserved.

Automated summary

This study used time-course transcriptome sequencing to investigate the differential transcriptional responses of Bipolaris oryzae in two rice hosts with contradictory infection responses. The results revealed similar regulation of fungal genes in susceptible and resistant hosts at an early stage, but a significantly higher number of upregulated genes were found in susceptible hosts at a later stage. Enrichment analysis showed that terms related to carbohydrate degradation, carbohydrate transport, and pathogenesis were extensively enriched in susceptible hosts at a later stage. The expression responses of secretory and effector proteins were also similar between the two hosts.