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Characterization of MAT1-2-7: a novel MAT gene in the wood-infecting fungus Huntiella omanensis

Andi Wilson: FABI, University of Pretoria

<div>Sexual reproduction in fungi is controlled by genes at the mating type (<em>MAT</em>) locus. Species of Ceratocystidaceae harbour the <em>MAT1-1-1, MAT1-1-2,</em> <em>MAT1-2-1</em> and <em>MAT1-2-7</em> genes at this locus. More specifically, <em>Ceratocystis</em> species, most of which are aggressive plant pathogens, possess all four genes at a single locus, characteristic of self-fertile ascomycetes. In contrast, saprobic <em>Huntiella</em> species possess either the <em>MAT1-1</em> genes or the <em>MAT1-2 </em>genes, resulting in a self-sterile mating system. A notable exception is the unisexual <em>H. moniliformis</em>, in which single spore isolates can undergo sexual reproduction, despite having only the <em>MAT1-2-1</em> and truncated <em>MAT1-2-7</em> genes. In this study, we determined whether the functional <em>MAT1-2-7</em> plays a role in sexual reproduction by preventing self-fertility as seen in <em>H. moniliformis</em>. A split marker knockout approach was used to replace the <em>MAT1-2-7</em> gene in <em>H. omanensis</em>, which is a close relative of <em>H. moniliformis,</em> with a Hygromycin resistance cassette. The results showed that while the <em>ΔMAT1-2-7</em> strain did not exhibit self-fertility, it does produce structures resembling proto-ascomata. The production of such structures in a self-sterile species hints at a role for <em>MAT1-2-7</em> in the sexual process. This is the first study to genetically manipulate a species of the Ceratocystidaceae, and the knockout protocol provides a tool to study biologically significant processes in this group of fungi.</div>