Amazing stuff! Too bad, humans run out of letters when it comes to LGBTQ+ or we cannot pronounce it anymore! 😄
In noticed lately, there appears to be more research being published on fungi and other microorganisms in recent times. See also my other recent blog post here.
"... This diversity has hampered sequencing efforts. The many divergent alleles make primer design all but impossible, thwarting the use of less expensive, targeted sequencing methods. This hurdle means that researchers wanting to sequence these fungi would need to rely on so-called next generation, short-read genomic sequencing technologies—methods which, given the number of individuals and the depth of sequencing needed to ensure accuracy, have simply been too expensive.
Now, though, lower costs of next generation technologies made sequencing so many individuals feasible. ... team were able to use newer, long-read sequencing to generate high-quality genomes that acted as scaffolds for accurate assemblies of the short reads. The combination of methods made it so the researchers could precisely pinpoint which parts of the MATA and MATB genetic regions were important for sex determination as well as count the number of different relevant variations in those two areas. Putting it all together, the team found that, contained within these unassuming shelf fungi, there could be a staggering 17,550 different combinations to choose from. ..."
From the abstract:
"Balancing selection, an evolutionary force that retains genetic diversity, has been detected in multiple genes and organisms, such as the sexual mating loci in fungi. However, to quantify the strength of balancing selection and define the mating-related genes require a large number of strains. In tetrapolar basidiomycete fungi, sexual type is determined by two unlinked loci, MATA and MATB. Genes in both loci define mating type identity, control successful mating and completion of the life cycle. These loci are usually highly diverse. ... (Hymenochaetales, Basidiomycota) possess a tetrapolar mating system, with multiple alleles. Here, we sequenced a hundred and eighty strains of three Trichaptum species. We characterized the chromosomal location of MATA and MATB, the molecular structure of MAT regions and their allelic richness. The sequencing effort was sufficient to molecularly characterize multiple MAT alleles segregating before the speciation event of Trichaptum species. Analyses suggested that long-term balancing selection has generated trans-species polymorphisms. Mating sequences were classified in different allelic classes based on an amino acid identity (AAI) threshold supported by phylogenetics. 17,550 mating types were predicted based on the allelic classes. In vitro crosses allowed us to support the degree of allelic divergence needed for successful mating. Even with the high amount of divergence, key amino acids in functional domains are conserved. We conclude that the genetic diversity of mating loci in Trichaptum is due to long-term balancing selection, with limited recombination and duplication activity. The large number of sequenced strains highlighted the importance of sequencing multiple individuals from different species to detect the mating-related genes, the mechanisms generating diversity and the evolutionary forces maintaining them."
From the authors summary:
"Fungi have complex mating systems, and basidiomycete fungi can encode thousands of mating types. Individuals with the same mating type cannot mate. This sexual system has evolved to facilitate sexual mating with offspring from different parents, increasing the chances to recombine into advantageous allelic combination and prune deleterious alleles. We explored the genomes of hundred and eighty strains, combined with experimental mating studies of selected strains, from a non-model organism (Trichaptum). We characterized the genomic regions controlling sex. The mating ability of the strains confirmed the role of the mating alleles observed in the genomic data. The detailed analyses of many strains allowed us to observe gene duplication and rearrangements within the mating loci, increasing the diversity within these loci. We supported previous suggestions of balancing selection in this region, an evolutionary force that maintains genomic diversity. These results supports that fungal strains are prone to outcross, which might facilitate the adaptation to new conditions."
This Fungus Has More Than 17,000 Sexes | The Scientist Magazine® Advances in sequencing technologies have finally allowed researchers to zero in on the genetic diversity underlying the incredible mating system of shelf fungi.
Two compatible strains of Trichaptum fuscoviolaceum
mating on a petri dish
