Global Sexual Fertility in the Opportunistic Pathogen <i>Aspergillus fumigatus</i> and Identification of New Supermater Strains

• Main Authors: Sameira S. Swilaiman, Céline M. O’Gorman, Wenyue Du, Janyce A. Sugui, Joanne Del Buono, Matthias Brock, Kyung J. Kwon-Chung, George Szakacs, Paul S. Dyer
• Format: Article
• Language: English
• Published: MDPI AG 2020-10-01
• Series: Journal of Fungi
• Subjects: <i>Aspergillus fumigatus</i>; sexual fertility; cleistothecia; supermater
• Online Access: https://www.mdpi.com/2309-608X/6/4/258

A sexual cycle in <i>Aspergillus fumigatus</i> was first described in 2009 with isolates from Dublin, Ireland. However, the extent to which worldwide isolates can undergo sexual reproduction has remained unclear. In this study a global collection of 131 isolates was established with a near 1:1 ratio of mating types. All isolates were crossed to <i>MAT1-1</i> or <i>MAT1-2</i> Irish strains, and a subset of isolates from different continents were crossed together. Ninety seven percent of isolates were found to produce cleistothecia with at least one mating partner, showing that sexual fertility is not limited to the Irish population but is a characteristic of global <i>A. fumigatus</i>. However, large variation was seen in numbers of cleistothecia produced per cross, suggesting differences in the possibility for genetic exchange between strains in nature. The majority of crosses produced ascospores with >50% germination rates, but with wide variation evident. A high temperature heat shock was required to induce ascospore germination. Finally, a new set of highly fertile <i>MAT1-1</i> and <i>MAT1-2</i> supermater strains were identified and pyrimidine auxotrophs generated for community use. Results provide insights into the potential for the <i>A. fumigatus</i> sexual cycle to generate genetic variation and allow gene flow of medically important traits.