Biology subjects

Brandstrom Durling, M.

Publications and source records attributed to Brandstrom Durling, M..

2 recordsLinked to original sources

bioRxiv2026

Homothallic or heterothallic? A genomic investigation into the sexual capabilities of the ascomycete fungus Clonostachys rosea

Modes of reproduction and sexual strategies strongly influence the genetic diversity and evolutionary potential of a species. The ascomycete fungus Clonostachys rosea is reported to be homothallic (sexually self-fertile), although a rapid decay of genome-wide linkage disequilibrium is also reported, something that is not in line with an obligate homothallic mode of reproduction. To investigate this phenomenon, we identified the mating-type (MAT1) locus in 66 genome-sequenced C. rosea strains under the hypothesis that each strain contains genes from both MAT1 idiomorphs. Eleven strains indeed contained both MAT1-1 and MAT1-2 genes, suggesting homothallism. However, most strains harboured either MAT1-1 or MAT1-2 genes and co-existed in North America, Europe and China, suggesting heterothallism. The MAT1 locus of heterothallic strains was highly conserved, and the linkage disequilibrium half decay distance was 1050 bp, suggesting sexual outcrossing. The presence of conserved MAT1-1 or MAT1-2 idiomorphs in strains of other Clonostachys species shows that heterothallism is likely the ancestral state. A phylogenetic analysis of 2800 single-copy orthologous genes revealed that homothallic and heterothallic strains separated in two well-supported clades, indicating a single lineage of homothallic C. rosea, likely originating in South America, followed by intercontinental dispersal. Homothallic C. rosea strains displayed higher nucleotide diversity than heterothallic strains, indicating a lack of outcrossing. This unique case of both homothallic and heterothallic lineages within the same species provides an opportunity to study the genomic consequences of selfing in very closely related strains.

evolutionary biology↗

bioRxiv2025

Mating Type Gene Divergence is Associated with Life Cycle Differentiation in Scots Pine Blister Rust

Reproductive systems are central to the evolutionary and ecological processes shaping population structure and adaptability. Rust fungi are a large group of obligate plant pathogens with complex life cycles and diverse reproductive modes. In the rust fungus Cronartium pini, which exists in both macrocyclic heteroecious and microcyclic autoecious forms, transitions between reproductive modes can be studied within a single species. Here, we used comparative genomics to analyse the structure, diversity, and organization of mating-type (MAT) loci across both forms of C. pini. We identified a canonical tetrapolar system in the heteroecious form, characterized by unlinked, multiallelic homeodomain (HD) and pheromone/receptor (P/R) loci, consistent with obligate outcrossing. In contrast, the autoecious form displayed distinct reproductive signatures, including MAT gene homozygosity in some samples--indicative of clonal reproduction--and MAT gene duplications in others, suggesting self-fertility or altered mating pathways. Three HD loci were detected, but only one exhibited high allelic diversity and was consistently present, indicating functional divergence. Expanded allelic diversity at the STE3.2 pheromone receptor further suggests plasticity at the P/R locus. Although allele sharing between life cycle forms was rare, isolated cases of shared MAT alleles suggest limited historical connectivity and possible trans-specific polymorphism. Together, our findings reveal flexibility in the mating system architecture of C. pini and suggest that transitions between sexual and asexual reproduction may be facilitated by retained, functionally ambiguous MAT structures. This work highlights C. pini as a powerful model for studying life cycle evolution and mating system transitions in rust fungi.

evolutionary biology↗