Podospora anserina

Ament‐Velásquez, Sandra Lorena; Vogan, Aaron A.

doi:10.1016/j.tim.2022.09.006

Cited by 2 publications

(3 citation statements)

References 9 publications

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“…A surprising finding of this study was the lack of population level signatures of balancing selection when calculated using window sizes common to such studies (Heller et al 2018; Ament-Velásquez 2020). It is well established that the mating locus as well as het genes are under negative frequency dependent selection, leading to balanced polymorphisms.…”

Section: Discussionmentioning

confidence: 76%

“…This prevents either allele from reaching fixation, and thus both alleles are maintained longer than would be expected by random processes, with alleles often shared between related species in trans-species polymorphisms (Charlesworth 2006). Such patterns have been found in the genera Neurospora, Cryphonectria , and Podospora (Wu et al 1998; Milgroom et al 2018; Ament-Velásquez 2020).…”

Section: Introductionmentioning

confidence: 66%

“…A recent analysis of balancing selection on the S gametic self-incompatibility locus showed that increased nucleotide diversity was seen several tens of kilobases from the selected locus (Veve et al 2022). Recent analysis of the fungus Podospora anserina showed that signatures of balancing selection could be determined from population level analysis looking at 10kb windows (Ament-Velásquez 2020). However, the general relationship between recombination rate and the size of the footprint is unclear, as the divergent region surrounding the MLO2b immunity gene in Capsella sp .…”

Section: Discussionmentioning

confidence: 99%

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Identification of heterokaryon incompatibility genes inAspergillus fumigatushighlights a narrow footprint of ancient balancing selection

Auxier

Zhang

Marquez

et al. 2022

Preprint

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In fungi, a phenomenon termed heterokaryon incompatibility restricts hyphal fusion to occurs within an individual as fusion between individuals leads to cell death. Generally, the genes involved are found to be under balancing selection from negative frequency dependent fitness. Here, we assess this in Aspergillus fumigatus, a human pathogenic fungus with an extremely high crossover rate. Using auxotrophic markers we screened sexual progeny for compatibility to identify genes involved in this process, the so-called het genes. In total, 5/148 (3.2%) offspring were compatible with a parent and 166/2142 (7.7%) sibling pairs were compatible, consistent with several segregating incompatibility loci. Genetic mapping resulted in five loci, four of which could be fine mapped to individual genes, of which we tested three through heterologous expression, confirming their causal relationship. Surprisingly, a population-level analysis of two available independent datasets did not show an increase in Tajima's D near these loci, normally a hallmark of balancing selection. However, analysis of closely related species did show trans-species polymorphisms across >10 million years, and even allele frequencies within A. fumigatus. Using available de novo assemblies, we show that these balanced polymorphisms are restricted to within several hundred base pairs flanking the coding sequence, potentially due to this species' high crossover rate. In addition to identifying the first het genes in an Aspergillus species, this work highlights the interaction of long-term balancing selection with a high recombination rate. Future mechanistic work on these het genes may provide novel routes for clinical therapies, as well as opportunities for strain improvement in biotechnology.

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Section: Discussionmentioning

confidence: 76%

Section: Introductionmentioning

confidence: 66%

Section: Discussionmentioning

confidence: 99%

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Identification of heterokaryon incompatibility genes inAspergillus fumigatushighlights a narrow footprint of ancient balancing selection

Auxier

Zhang

Marquez

et al. 2022

Preprint

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Sheltered load in fungal mating-type chromosomes revealed by fitness experiments

Guyot,

Chahine,

Lalanne

et al. 2024

Preprint

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Sex chromosomes and mating-type chromosomes can carry large regions with suppressed recombination. In these non-recombining regions, recessive deleterious mutations are expected to occur, as i) they are predicted to accumulate as a result of lower efficacy of selection, and ii) they may even pre-exist and drive the evolution of recombination suppression. Multiple genomic analyses have indirectly inferred the presence of deleterious mutations in sex and mating-type chromosomes, but direct experimental evidence remains scarce. Here, we performed fitness assays in fungi with megabase-large and young non-recombining regions around the mating-type locus, using theSchizothecium tetrasporumandPodospora anserinaspecies complexes, to test whether heterokaryons (diploid-like, heterozygous at the mating-type locus) exhibited a fitness advantage over homokaryons (haploid-like, with a single mating-type allele), in terms of spore germination dynamics or mycelium growth speed, under different conditions of light and temperature. We found a faster growth of heterokaryons compared to one of the homokaryons forP. anserinaat 18°C, forS. tetrasporumandS. tritetrasporumat 22°C under light, and also at 22°C in the dark forS. tetrasporum. These findings suggest the presence of a sheltered load, i.e. recessive deleterious mutations at the heterozygous state in or near non-recombining regions, as these species are highly homozygous otherwise. Leveraging on the experimental assets of fungi, allowing cultivating separately haploid-like and diploid-like life stages, our experiments provided one of the rare direct experimental evidence of sheltered load around mating-compatibility loci, which is crucial for our understanding of sex-related chromosome evolution.

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Podospora anserina

Cited by 2 publications

References 9 publications

Identification of heterokaryon incompatibility genes inAspergillus fumigatushighlights a narrow footprint of ancient balancing selection

Identification of heterokaryon incompatibility genes inAspergillus fumigatushighlights a narrow footprint of ancient balancing selection

Sheltered load in fungal mating-type chromosomes revealed by fitness experiments

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