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Mating strategies in the Ceratocystidaceae that includes pathogens of trees and agronomic crop plants

Markus Wilken: Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria

<div>The Ceratocystidaceae (Microascales) include a biologically diverse group of fungi currently accommodating at least ten distinct genera. Among these, <em>Ceratocystis</em>, <em>Endoconidiophora</em> and <em>Thielaviopsis</em> are well known plant-pathogens, in contrast to <em>Huntiella</em> that are saprobes of little economic importance. Genome sequences are available for more than 25 species spanning seven genera of the Ceratocystidaceae. This resource provides an opportunity to study the mating systems, and more specifically the mating-type genes in these species. In this study the mating-type genes and <em>MAT1</em> locus was reconstructed for species in the family. Our results showed that all species capable of unidirectional mating-type switching shared a <em>MAT1</em> locus structure typical of this reproductive strategy. This included two direct repeats that flank the <em>MAT1-2</em> genes. Species of <em>Huntiella</em>, <em>Thielaviopsis</em> and <em>Bretziella </em>are known to be heterothallic, but differences in their gene content were evident among the <em>MAT1</em> loci in these species. Complete and apparently functional <em>MAT1</em> loci were also characterised from several species that are seemingly asexual, raising the possibility of cryptic sexual cycles in these fungi. The results provide a robust framework to study the evolution of sexual reproduction in not only the Ceratocystidaceae, but within the order Microascales as a whole.</div>