P-693 - Characterizing the reduced genome of the palm pathogen Thielaviopsis ethacetica

The fungal family Ceratocystidaceae (class Sordariomycetes) includes several insect- and non-insect associated plant pathogens. These pathogens are characterized by reduced assembly size as well as gene count. On average, a 36% and 42% reduction in genome size and gene count, respectively, was observed for Ceratocystidaceae when compared to 614 Sordariomycete genomes. The gene content of insect-associated fungi in genus Ceratocystis has been previously investigated but little is known about genus Thielaviopsis. For this study, palm pathogen T. ethacetica, assembly size 30 Mb and 7,304 genes, was utilized. To identify the genes and pathways absent in T. ethacetica, a comparative analysis of 14 Sordariomycete pathogens was conducted. A total of 185,042 proteins were clustered into 15,831 orthogroups, that revealed expansion and contraction for 23 and 2,156 gene families, respectively, in the Thielaviopsis clade. Initial analysis identified a reduction in the number of CAZymes, particularly glycosyl hydrolases (GH) and auxiliary activities (AA) in the T. ethacetica genome. A similar decreasing trend for proteases, specifically serine- and metallo-proteases was identified. Analysis based on KEGG annotation uncovered that biotin synthesis as well as HOG pathway was missing from T. ethacetica. This pilot analysis offers clues about the extent of gene losses in T. ethacetica. However, increased sampling of closely related species and integration of gene expression data would help understand the impact of these gene losses on host-pathogen interaction.