Graduate Research Assistant University of Florida GAINESVILLE, Florida
Body of Abstract: Sorghum is adapted to a wide variety of environments, but its productivity and sustainability can be hindered by fungal pathogens. Colletotrichum sublineola is the causal agent of anthracnose, resulting in leaf blight, stalk rot, and head blight in susceptible sorghums. The spread of anthracnose has led to a reliance on the application of fungicides for disease control. The development of anthracnose-resistant cultivars can provide a more sustainable and economical means for disease management. Previously, a genome-wide association study (GWAS) of the sorghum association panel (SAP) identified the candidate resistance gene Sobic.005G172300 encoding an F-box protein. Sequence analysis of the resistance allele revealed amino acid variations in the predicted protein relative to the susceptible reference BTx623, but the impact on protein function remains unclear. Analysis of gene expression following infection with C. sublineola demonstrated that the expression of Sobic.005G172300 increases during the biotrophic phase of infection in sorghum accessions harboring the resistance allele. Subsequent transcriptome analysis, gene coexpression networks, and gene regulatory networks of inoculated and mock-inoculated seedlings of resistant and susceptible accessions indicate Sobic.005G172300 modulates an oxidative burst and decrease in ascorbic acid content during the biotrophic phase of infection. These changes in reactive oxygen species and ascorbic acid concentrations are hypothesized to be achieved by targeting proteins for polyubiquitination through the SCF E3 ubiquitin ligase, followed by their degradation via the proteasome. The identification and characterization of Sobic.005G172300 provides insights into the molecular mechanisms underlying anthracnose resistance in sorghum and will facilitate the development of more sustainable disease management strategies.