Biology subjects

Branco, S.

Publications and source records attributed to Branco, S..

5 recordsLinked to original sources

bioRxiv2026

Not all roads lead to selfing: mating-system stability in an invasive ectomycorrhizal fungus

Baker's rule predicts that selfing is a beneficial trait for colonizers, whose prediction in the kingdom Fungi is reinforced by recent work showing the invasive ectomycorrhizal basidiomycete Amanita phalloides with self-incompatibility (SI) system has evolved unisexual reproduction in its introduced range. Unlike in plants, the multiallelic SI system of basidiomycetes does not fully prevent selfing among the meiotic offspring of a single dikaryotic (diploid) parent. This distinction allows observation of an intermediate state of selection where selfing is preferred in a species with SI system during colonization before a change in self-incompatibility architecture. Here, we analyzed the genomes of 189 isolates of the ectomycorrhizal basidiomycete Suillus luteus collected from both its native European range and five independently introduced regions to test whether selfing rates increase and whether the SI system had degraded after introduction. Unlike the A. phalloides case, we found no evidence of unisexual reproduction or loss of the SI system in the introduced ranges of S. luteus. Rather, all introduced populations maintained outcrossing rates higher than random mating as in the native populations. However, selfing events were detected in three individuals from a single introduced population, representing the first documented case of selfed sporocarps of Boletales fungi. Our works in S. luteus demonstrates that although selfing is possible in this species, it is not favored during colonization, potentially due to inbreeding depression and higher population density, highlighting the complex interaction among the invasion biology, genetics, and the colonizing context.

evolutionary biology↗

bioRxiv2026

Global population structures and demographic history of Suillus luteus, a pine co-introduced ectomycorrhizal fungus associated with exotic forestry and invasion.

Human colonization since the 19th century has resulted in the global spread of pines across the Southern Hemisphere, well beyond their original northern boreal distribution. Such introductions moved not only the pines but also expanded the distribution of their symbiotic partners. Although the introduction of pines is documented through historical records, little is known about the introduction history of their ectomycorrhizal fungi, which are critical symbionts for the survival and invasion of pines. Using Suillus luteus as an example, population genomic analyses of 208 individuals across both native and introduced ranges showed that all introductions originated from Europe, likely mediated by human activities along with pine introductions. With the exception of North America, introduced populations were genetically differentiated from the Europe population, with varying magnitudes of population expansion in different introduced regions, often linked to forestry practices. Genetic variation within the native European population followed isolation by distance, but not in the introduced range, highlighting the disparity in the spatial genetic patterns of native versus exotic habitats. This study provides insight into the population genetics of a globally introduced ectomycorrhizal fungus whose introduction process is likely applicable to other pine-co-introduced ectomycorrhizal fungi.

evolutionary biology↗

bioRxiv2023

Comparative transcriptomics provides insight into molecular mechanisms of zinc tolerance in the ectomycorrhizal fungus Suillus luteus

Zinc is a major soil contaminant and high zinc levels can disrupt growth, survival, and reproduction of fungi. Some fungal species have evolved zinc tolerance through cell processes mitigating zinc toxicity, though the genes and detailed mechanisms underlying fungal zinc tolerance remain unexplored. To fill this gap in knowledge, we investigated the gene expression of zinc tolerance in the mycorrhizal fungus Suillus luteus. We found that zinc tolerance in this species is both a constitutive and environmentally dependent trait. Highly differentially expressed genes were predicted to be involved in transmembrane transport, metal chelation, oxidoreductase activity, and signal transduction. Some of these genes were previously reported as candidates for S. luteus zinc tolerance, while others are reported here for the first time. Overall, we found S. luteus zinc tolerance is associated with differences in expression of genes involved in metal exclusion and immobilization, as well as recognition and mitigation of metal-induced oxidative stress. Our results contribute to understanding the mechanisms of fungal metal tolerance and pave the way for further research on the role of metal tolerance in mycorrhizal associations.

genomics↗

bioRxiv2021

Fungal communities from geothermal soils in Yellowstone National Park

Geothermal soils offer unique insight into the way extreme environmental factors shape communities of organisms. However, little is known about the fungi growing in these environments and in particular how localized steep abiotic gradients affect fungal diversity. We used metabarcoding to characterize soil fungi surrounding a hot spring-fed thermal creek with water up to 84 {degrees}C and pH 10 in Yellowstone National Park. We found a significant association between fungal communities and soil variable principal components, and we identify the key trends in co-varying soil variables that explain the variation in fungal community. Saprotrophic and ectomycorrhizal fungi community profiles followed, and were significantly associated with, different soil variable principal components, highlighting potential differences in the factors that structure these different fungal trophic guilds. In addition, in vitro growth experiments in four target fungal species revealed a wide range of tolerances to pH levels but not to heat. Overall, our results documenting turnover in fungal species within a few hundred meters suggest many co-varying environmental factors structure the diverse fungal communities found in the soils of Yellowstone National Park.

ecology↗

bioRxiv2019

Incipient local adaptation in a fungus: evolution of heavy metal tolerance through allelic and copy-number variation

Human-altered environments can shape the evolution of organisms. Fungi are no exception, though little is known about how they withstand anthropogenic pollution. Here, we document incipient polygenic local adaptation in the mycorrhizal fungus Suillus luteus driven by recent soil heavy metal contamination. Genome scans across individuals from recently polluted and nearby unpolluted soils in Belgium revealed no evidence of population structure but detected allelic divergence and gene copy number variation in genes involved in metal exclusion, storage, immobilization, and reactive oxygen species detoxification. Standing genetic variation included multiple alleles of small effects contributing to heavy metal tolerance, suggesting the existence of different strategies to withstand contamination. These variants were shared across the whole population but under selection in isolates exposed to pollution. Together, our results point to S. luteus undergoing the initial steps of adaptive divergence and contribute to understanding the processes underlying local adaptation under strong environmental selection.

evolutionary biology↗