BackgroundSeptins are cytoskeletal proteins important in cell division and in establishing and maintaining cell polarity. Although septins are found in various eukaryotes, septin genes had the richest history of duplication and diversification in the animals, fungi and protists that comprise opisthokonts. Opisthokont septin paralogs encode modular proteins that assemble into heteropolymeric higher order structures. The heteropolymers can create physical barriers to diffusion or serve as scaffolds organizing other morphogenetic proteins. How the paralogous septin modules interact to form heteropolymers is still unclear. Through comparative analyses, we hoped to clarify the evolutionary origin of septin diversity and to suggest which amino acid residues were responsible for subunit binding specificity.ResultsHere we take advantage of newly sequenced genomes to reconcile septin gene trees with a species phylogeny from 22 animals, fungi and protists. Our phylogenetic analysis divided 120 septins representing the 22 taxa into seven clades (Groups) of paralogs. Suggesting that septin genes duplicated early in opisthokont evolution, animal and fungal lineages share septin Groups 1A, 4 and possibly also 1B and 2. Group 5 septins were present in fungi but not in animals and whether they were present in the opisthokont ancestor was unclear. Protein homology folding showed that previously identified conserved septin motifs were all located near interface regions between the adjacent septin monomers. We found specific interface residues associated with each septin Group that are candidates for providing subunit binding specificity.ConclusionsThis work reveals that duplication of septin genes began in an ancestral opisthokont more than a billion years ago and continued through the diversification of animals and fungi. Evidence for evolutionary conservation of ~ 49 interface residues will inform mutagenesis experiments and lead to improved understanding of the rules guiding septin heteropolymer formation and from there, to improved understanding of development of form in animals and fungi.Electronic supplementary materialThe online version of this article (10.1186/s12862-018-1297-8) contains supplementary material, which is available to authorized users.

Evidence from both population genetics and a laboratory sexual cycle indicate that sex is common in the fungus Aspergillus fumigatus. However, the impact of sexual reproduction has remained unclear. Here, we show that meiosis in A. fumigatus involves the highest known recombination rate, producing ~29 crossovers per chromosome. This represents the highest known crossover rate for any Eukaryotic species. We validate this recombination rate by mapping resistance to acriflavine, a common genetic marker. We further show that this recombination rate can produce the commonly encountered TR34/L98H azole-resistant cyp51A haplotype in each sexual event, facilitating its rapid and global spread. Understanding the consequences of this unparalleled crossover rate will not only enrich our genetic understanding of this emergent human pathogen, but of meiosis in general.

Chen et al. recently reported evidence for inter-nucleus recombination in arbuscular mycorrhizal fungi (Chen et al., 2018a). Here, we report a reanalysis of their data. After filtering the data by excluding heterozygous sites in haploid nuclei, duplicated regions of the genome, and low-coverage depths base calls, we find the evidence for recombination to be very sparse.

Ancestral predisposition toward a domesticated lifestyle in the termite-cultivated fungus Termitomyces Highlights d Insect-fecal associations predate the domestication of Termitomyces fungi d A set of morphological traits predisposed lyophylloid fungi toward domestication d Insect-associated lyophylloid fungi have reduced plantdegrading capabilities d This symbiosis may have been facilitated by pre-adaptation of both partners