Unisexual reproduction in Huntiella moniliformis

Abstract

Sexual reproduction in fungi is controlled by genes present at the mating type (MAT) locus, which typically harbours 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.

Genetic basis for high population diversity in Protea-associated Knoxdaviesia

“…The genes that typically flank the downstream region of MAT1 loci have shifted to an upstream position in C. fimbriata. A similar shift is evident in the two studied Huntiella species, although the APN2 gene has shifted to a genomic position far from the MAT1 locus (Wilson et al, 2015).…”

“…2A). The position of this intron in the omanensis (Wilken et al, 2014;Wilson et al, 2015). This domain was well conserved between Knoxdaviesia and the Ceratocystidaceae species, although C. fimbriata displays several deviations from amino acids that remain conserved in Knoxdaviesia and Huntiella ( Fig.…”

“…The pairings, therefore, included four MAT1-1 vs. MAT1-2 crossings and two negative controls (MAT1-1 vs. MAT1-1 and MAT1-2 vs. MAT1-2). All six pairings were made in triplicate by (1) sub-culturing two strains approximately two cm apart (Wilson et al, 2015),…”

“…The other two Ceratocystidaceae species studied are members of the genus Huntiella that typically show a saprophytic association with tree wounds (Van Wyk et al, 2006). Both of the studied species in this genus are heterothallic (Wilson et al, 2015), although H. moniliformis is also capable of unisexual reproduction; since it contains a single MAT1 idiomorph, yet produces ascomata (Wilson et al, 2015). One trait that unites the diverse mating strategies in Ceratocystidaceae is their deviation from the consensus gene order of the Sordariomycetes.…”

“…Although it is widely accepted that the presence of both idiomorphs is necessary for sexual reproduction, fungal mating strategies are diverse and many exceptions to this rule have been observed (Heitman, 2015). For example, some species are self-fertile despite only possessing one MAT1 idiomorph (unisexual reproduction; Alby and Bennett, 2011;Glass and Smith, 1994;Lin et al, 2005;Wilson et al, 2015).…”