Page 92 - University of Pretoria Research Review 2017

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How fungi do it
Andi Wilson and Brenda Wingfield, Forest Molecular Genetics Research Programme, FABI
While it might seem strange that such seemingly simple organisms are even able to sexually reproduce, fungi exhibit some of the most fascinating and diverse sexual strategies of all the species on this planet.
Researchers at the Forestry and Agricultural Biotechnology Institute (FABI) study sexual reproduction in a number of fungi, including important tree pathogens. Understanding how sexual reproduction takes place in disease-causing fungi is specifically important as it provides a platform from which to develop management, treatment and prevention strategies. Such strategies are critical if the introduction and spread of fungal pathogens are to be controlled from continent to continent and forest to forest.
Andi Wilson, a doctoral student working with Professor Brenda Wingfield, has discovered that Huntiella moniliformis, a species from a family of notorious plant pathogens, is unisexual. This means that this fungus
is able to sexually reproduce in the complete absence of a mating partner and without genes that have long been thought of as essential for sex. Understanding this system has significant ramifications for the management of this and potentially other unisexual fungi. Recently, Andi and her colleagues were able to show that it is likely that the uncontrolled expression of mating pheromones in H. moniliformis allows it to sexually reproduce in isolation.
Postdoctoral fellows Markus Wilken and Melissa Simpson are investigating mating type switching in
the genus Ceratocystis. Melissa has recently shown
in her PhD work that these species need to delete
an entire region of the MAT locus in order for sexual recombination to occur. Markus has shown that
species in related genera also undergo this mating type switching, indicating that this mechanism is perhaps not as unique as had been thought previously.
In heterothallic, or self-sterile fungal species,
identifying the genes in the MAT locus provides tools
to understand the genetic diversity of a species. In some cases, disease outbreaks are clonal lineages, whereas in others, the fungus may be more diverse. The latter are more difficult to control and it is thus essential to study the genetic diversity of a fungus
early on in the diagnostic process. With the decreasing costs of genome sequences, a number of researchers in the group, including Tuan Duong, Aquillah Kanzi
and Wilma Nel, are sequencing increasing numbers
of fungal genomes in order to elucidate the MAT locus in the species they study. While mating and sexual recombination of fungi may on the surface seem to be somewhat obscure, understanding the mating system of a fungus, and particularly a tree pathogen, is a critical first step in developing management strategies to combat these pathogens. Trees are after all an essential component of our natural environment, literally providing the oxygen we breathe.
Recent research articles on sexual reproduction in tree pathogens have been published in the journals Fungal Biology, Fungal Biology Reviews, Fungal Genetics and Biology, and PLoS One.
Andi Wilson