Aspergillus fumigatus is an opportunistic human pathogen that causes a range of allergic and invasive diseases in severely immunocompromised individuals, with a very high mortality rate typically in excess of 50%. A functional sexual cycle was discovered in 2009 and a highly fertile ’supermater’ pair, AFB62 and AfIR928, was later identified from a collection of 50 isolates. Here we describe the results of a larger, worldwide fertility screen and present an additional ’supermater’ pair. A set of 126 clinical and environmental A. fumigatus isolates were crossed against two Irish reference strains of each mating type. A subset of the eight most-fertile strains was then tested in all pairwise combinations. The pairing of isolates 47-169 x 47-154 had consistently high mating efficiency and outcrossing ability after four weeks, therefore it was chosen as an additional ’supermater’ pair for community use in mating projects. It is important to have alternative tester strains to allow for unexpected mating differences when crossing isolates of diverse genetic origins. This is because factors such as heterokaryon incompatibility (het) loci and single nucleotide polymorphisms, can considerably influence sexual compatibility. The worldwide fertility screen found that approximately 85% of isolates are sexually fertile, indicating that sexual reproduction should be possible in nature when suitable environments are present. Next, the plasticity of sexual crossing conditions was tested, to determine whether they could be manipulated to increase fertility in crosses involving low-fertility strains of interest. A range of environmental and growth conditions were examined, including incubation temperature, CO2 level, and oatmeal agar type. Fertility levels were significantly affected by certain parameters. Work is ongoing to integrate these factors to further optimize fertility in the ’supermater’ pairs.
Full conference title:
27th Fungal Genetics Conference
- Fungal Genetics Conference 27th (2013)