Basic research into how mold fungi reproduce

FAU researchers find an important puzzle piece in the sexual cycle of an infectious mold fungus

Sexual reproduction is widespread in the animal and plant kingdoms and serves to recombine genetic information. Fungi can also go through a sexual cycle, during which they secrete messenger substances, known as pheromones, and detect them using suitable receptors. Scientists were already aware that the mold fungus “Aspergillus fumigatus” that can potentially trigger disease in humans had most of the required components. However, the existence of one of the involved gender-specific pheromones remained unclear. Working in collaboration with researchers in Germany and abroad, the working group led by Prof. Dr. Sven Krappmann from Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) has now successfully identified a previously unknown pheromone.

In the fungal kingdom there are numerous examples of sexual reproduction, involving the recombination of genetic material. During the sexual cycle and the division of the cell nucleus, known as meiosis, fruiting bodies containing meiospores are produced. The underlying genetic processes mean that the resulting recombinant microorganisms may have new, potentially beneficial properties for the fungus. Microbiologists suspect that these processes are particularly significant for the pathogenic properties, or virulence, and resistance behavior of human pathogenic fungi. Detailed research into these processes and their consequences is therefore hugely significant for a basic understanding of fungal pathogens.

“Aspergillus (A.) fumigatus” is a fungus with ubiquitous spores that we breathe in permanently. It is considered an opportunistic pathogen, as it does not pose any health risks to healthy people. However, in people with a severely weakened immune system or after allergic reactions it may trigger an illness known as aspergillosis. Systemically spreading forms of aspergillosis predominantly affect patients with suppressed immune systems and may under certain circumstances take a life-threatening course.

FAU researchers deliver an important piece of the puzzle

For a long time, it was unclear whether and in what form A. fumigatus had a sexual cycle, although it was clear that the ascomycete formed important components for this to be the case, for instance mating types of pheromone receptors and at least one sexual pheromone. In 2009, a British research group discovered that A. fumigatus develops sexual fruiting bodies known as cleistothecia with recombinant spores. However, until now scientists were unaware of the existence of a pheromone classed as an a-factor pheromone that appears crucial for the mutual recognition of two A. fumigatus micro-organisms of different sexes.

An international group of fungal geneticists led by Prof. Dr. Sven Krappmann was able to make a decisive contribution in this respect, which has recently been published in the journal Current Biology: Researchers succeeded not only in proving the existence of the pheromone, but were also able to determine its identity and function in the sexual cycle thanks to various analyses.

“The successful identification of the a-factor from A. fumigatus was due to the close collaboration among researchers from different disciplines,” explains Prof. Sven Krappmann.

The identification of the a-factor pheromone from A. fumigatus closes a significant gap in our knowledge concerning the sexual reproduction of ascomycetes. The new findings are useful, for instance, for future studies on the formation of species in the fungal kingdom. One question that arises, for example, is how similar fungus species such as related Aspergillus species protect themselves from mating with the wrong partner.

Further information:

Prof. Dr. Sven Krappmann
Professorship for Microbiology and Immunology
Phone:+49 9131 85-32580
sven.krappmann@uk-erlangen.de