Abstract:
Sexual reproduction in fungi is controlled by genes present at the mating type (MAT) locus, which typically
harbors transcription factors that influence the expression of many sex-related genes. The MAT locus
exists as two alternative idiomorphs in ascomycetous fungi and sexual reproduction is initiated when
genes from both idiomorphs are expressed. Thus, the gene content of this locus determines whether a
fungus is heterothallic (self-sterile) or homothallic (self-fertile). Recently, a unique sub-class of homothallism
has been described in fungi, where individuals possessing a single MAT idiomorph can reproduce
sexually in the absence of a partner. Using various mycological, molecular and bioinformatic techniques,
we investigated the sexual strategies and characterized the MAT loci in two tree wound-infecting fungi,
Huntiella moniliformis and Huntiella omanensis. H. omanensis was shown to exhibit a typically heterothallic
sexual reproductive cycle, with isolates possessing either the MAT1-1 or MAT1-2 idiomorph. This was
in contrast to the homothallism via unisexual reproduction that was shown in H. moniliformis, where only
the MAT1-2-1 gene was present in sexually reproducing cultures. While the evolutionary benefit and
mechanisms underpinning a unisexual mating strategy remain unknown, it could have evolved to minimize
the costs, while retaining the benefits, of normal sexual reproduction.
