Rapid accumulation of mutations in growing mycelia of a hypervariable fungus Schizophyllum commune

Abstract

<jats:title>Abstract</jats:title><jats:p>The number of mutations that occur per nucleotide per generation varies between species by several orders of magnitude. In multicellular eukaryotes, the per generation mutation rate depends both on the per cell division mutation rate and on the number of germline cell divisions per generation. In a range of species, from fungi to humans, the number of germline cell divisions is lower than that of somatic cells, reducing the mutation burden on the offspring. The basidiomycete <jats:italic>Schizophyllum commune</jats:italic> has the highest level of genetic polymorphism known among eukaryotes. In a previous study, it was also found to have a high per generation mutation rate, probably contributing to its high polymorphism. However, this rate has been measured only in a breeding experiment on Petri dishes, and it is unclear how this result translates to natural populations. Here, we used an experimental design that measures the rate of accumulation of <jats:italic>de novo</jats:italic> mutations in a linearly growing mycelium. We show that <jats:italic>S. commune</jats:italic> accumulates mutations at a uniform rate of 1.4·10<jats:sup>−7</jats:sup> substitutions per nucleotide per meter of growth, which is 3 orders of magnitude higher than the corresponding rates in the oak <jats:italic>Quercus robur</jats:italic> and the fungus <jats:italic>Armillaria gallica</jats:italic>. This figure is consistent with the estimate obtained before, and suggests the lack of a dedicated germline in this system. If so, even a low per cell division mutation rate can translate into a very high per generation mutation rate when the number of cell divisions between consecutive meioses is large.</jats:p>

Population genetic analysis reveals the role of natural selection and phylogeography on genome-wide diversity in an extremely compact and reduced microsporidian genome

“…Assuming a resting time of three to six months, its mutation rate might be between 9.98 × 10 −12 and 1.50 × 10 −11 per site per generation (2.24 × 10 −12 -2.98 × 10 −11 ). These values are comparable with what has previously been reported for fungi (see e.g., [38–40]).…”

“…In By calibrating the phylogenetic tree of O. colligata with the divergence time of the Western Eurasian and East Asian (plus North American) host lineages, a time which has previously been estimated using fossil data [36], we provide the first estimated mutation rate of a microsporidium. Fungi, to which the microsporidia are phylogenetically associated, have been shown to have low mutation rates (e.g., [38][39][40]). Our estimate for O. colligata falls within the range of previously published mutation rate estimates of fungi.…”

Biocatalyst collection and heterologous expression of sesquiterpene synthases from basidiomycetous fungi: Discovery of a novel sesquiterpene hydrocarbon

“…However, the mutations seemed to have no detrimental effects on the catalytic performance of the STSs. Polymorphic differences might be common in basidiomycetes (Bezmenova et al, 2020; Ide et al, 2012). Several candidates were amplified as immature cDNAs whose open reading frame was shifted by intronic sequences, which were incorrectly spliced; filamentous fungi may sometimes allow a deleterious splicing event (Ide et al, 2012; Nazir et al, 2010; Permana et al, 2022).…”