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Pheromone expression in the unisexual fungus, Huntiella moniliformis

Andi Wilson: FABI, University of Pretoria

<div>Unisexuality is a reproductive strategy which enables fungi that are normally self-sterile, to reproduce in the absence of a compatible mating partner. The process is well documented in two human pathogens, but has also been described in the wood-infesting <em>Huntiella moniliformis</em>. This fungus is a member of the Ceratocystidaceae, a family that includes known pathogens of agronomic crops and trees. In this study, a comparative transcriptomics approach was used to elucidate the molecular mechanisms responsible for unisexuality in <em>H. moniliformis</em>. By sequencing RNA from vegetative and sexually-competent isolates of <em>H. omanensis</em>, a self-sterile relative of <em>H. moniliformis</em>, we identified genes important for sex. This was compared to similar data obtained from <em>H. moniliformis</em> to detect significant differences between the two reproductive pathways. Notably, the pheromones in <em>H. moniliformis</em> were expressed in a mating-type-independent manner. This contrasted with pheromone expression in <em>H. omanensis</em>, which exhibited a strict mating-type-dependence. <em>H. moniliformis</em> also expressed both pheromone receptors, suggesting that it can recognize and respond to both pheromones. The results indicated that this unusual pheromone expression system may play a role in the unisexual capabilities of <em>H. moniliformis</em>. Given the strong link between unisexuality and pathogenicity in the human pathogens, further investigation into this mating strategy in <em>H. moniliformis</em> would be worthwhile.</div>