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POSTERS: Plant Defense Responses I

P-521 - Genomic and transcriptomic insights into Ustilaginoidea virens and host defense mechanisms in rice false smut

Monday, August 4, 2025
4:30 PM - 5:15 PM HST
Location: Exhibit Hall 3
Abstract Text: Rice False Smut, caused by Ustilaginoidea virens, is an “old but new” disease threatening global rice production and quality. Despite its long history and widespread fungicide use, control remains ineffective, and the lack of genomic resources has hindered the understanding of pathogen biology and host resistance. To address this gap, the Philippine U. virens isolate PFS109-1 was sequenced. The integration of long-read and short-read sequencing generated a nearly gap-free genome of 35.8 Mbp with 95.9% completeness. A total of 4,304 candidate effectors, including 134 secreted effectors, were identified as potential pathogenicity factors. Whole-genome sequencing of 34 isolates across 11 Philippine regions revealed six major clades with no correlation between geographic origin and pathogen clustering, suggesting high inter-island mobility. Dual transcriptomic analysis of U. virens infecting a susceptible (IR10F360) and a resistant (NSICRc170) rice cultivar at 2-, 4-, and 6-days post-inoculation showed no distinct pathogen transcriptomic profiles between hosts. In total, 41 and 6 differentially expressed genes were identified in the resistant and susceptible cultivars respectively, across all three timepoints. The resistant cultivar exhibited an upregulation of Bet v I/Major Latex domain proteins and a downregulation of metabolism-related genes, likely restricting pathogen access to nutrients. In summary, our study offers valuable insights into the pathogen biology and the host’s defense mechanisms against rice false smut, advancing efforts toward genetic control of the disease