Abstract:
Colletotrichum species are known to engage in unique sexual behaviors that differ significantly from the mating strategies of other filamentous
ascomycete species. For example, most ascomycete fungi require the expression of both the MAT1-1-1 and MAT1-2-1 genes to induce
sexual reproduction. In contrast, all isolates of Colletotrichum harbor only the MAT1-2-1 gene and yet, are capable of recognizing
suitable mating partners and producing sexual progeny. The molecular mechanisms contributing to mating types and behaviors in
Colletotrichum are, however, unknown. A comparative genomics approach analyzing 35 genomes, representing 31 Colletotrichum species
and two Verticillium species, was used to elucidate a putative molecular mechanism underlying the unique sexual behaviors observed in
Colletotrichum species. The existence of only the MAT1-2 idiomorph was confirmed across all species included in this study. Comparisons
of the loci harboring the two mating pheromones and their cognate receptors revealed interesting patterns of gene presence and absence.
The results showed that these genes have been lost multiple, independent times over the evolutionary history of this genus. These losses
indicate that the pheromone pathway no longer plays an active role in mating type determination, suggesting an undiscovered mechanism
by which mating partner recognition is controlled in these species. This further suggests that there has been a redirection of the underlying
genetic mechanisms that regulate sexual development in Colletotrichum species. This research thus provides a foundation from which further
interrogation of this topic can take place.
