Genome-Wide Characterization of the Botryosphaeria dothidea GH28 Family Reveals BdGH28_3 Contributes to Virulence on Chinese Hickory

Abstract

Chinese hickory (Carya cathayensis Sarg.) is an economically important tree species widely cultivated in southeastern China, where trunk canker disease caused by Botryosphaeria dothidea poses a serious threat to tree health and production. Pectin-degrading enzymes are important virulence-associated factors that facilitate fungal colonization and host tissue maceration, but their evolutionary diversification and functional roles in B. dothidea during woody host infection remain poorly understood. Comparative genomic analysis revealed lineage-specific variation in the GH28 glycoside hydrolase family among the examined Botryosphaeriaceae species, with B. dothidea exhibiting an expanded GH28 repertoire relative to the analyzed species. Expression analysis and functional assays revealed that BdGH28_3 showed the highest transcript abundance during infection stage and contributed to the full virulence of B. dothidea. A predicted protein–protein interaction (PPI) network suggested potential associations between BdGH28_3 and other pectinolytic enzymes, including polygalacturonases, pectin lyases, and pectinesterases. Collectively, these findings identify GH28 diversification as a distinctive feature of the B. dothidea genome and establish BdGH28_3 as a virulence-associated member, providing a foundation for investigating GH28-mediated pathogenicity in woody hosts.