Characterization and organization of telomeric-linked helicase (tlh) gene families in Fusarium oxysporum.

Telomere-linked RecQ helicase (tlh) genes have been reported in several fungi and a choanoflagellate in the regions adjacent to the terminal telomere repeats. In this study, we explored the Telomere-linked RecQ helicase (tlh) genes in four strains of Fusarium oxysporum, offering new insights into their genomic structure, functional motifs, and impact on chromosomal ends. We conducted a comprehensive analysis, comparing the tlh genes of F. oxysporum with those previously identified in other organisms and uncovering significant similarities. Through comparative genomics, we identified conserved protein motifs across these genes, including a TLH domain, C₂H₂, and RecQ helicase motifs. Our phylogenetic analysis positions the F. oxysporum tlh genes in a cluster with other known tlhs, suggesting a shared evolutionary origin. Mutation analysis revealed a relatively low level of deleterious mutations in tlh gene paralogs, with a notable proportion of full-size structures maintained across strains. Analysis of subtelomeric sequences indicates that a region with almost identical sequences flanks the majority of chromosome ends, termed tlh-containing region (TLHcr), across these strains. The presence of TLHcrs at chromosome ends, either as single entities or in arrays, underscores their potential role in telomere function and genome stability. Our findings provide a detailed examination of tlh genes in four strains of F. oxysporum, laying the groundwork for future studies on their biological significance and evolutionary history in fungal genomes.