Biology subjects

Bastiaans, E.

Publications and source records attributed to Bastiaans, E..

4 recordsLinked to original sources

bioRxiv2026

Cheating (re)shapes pathogen virulence and antifungal resistance

Filamentous fungi grow as fused, multinucleate networks that share secreted public goods vs private goods. We asked whether this sharing enables "cheater" nuclei to increase in frequency by exploiting goods produced by other nuclei, and whether such social conflict shapes virulence and antifungal resistance. We tested this in the gray mold pathogen Botrytis cinerea by contrasting an extracellular detoxification trait, a public good (enzymatic hydrolysis of the tomato saponin alpha-tomatine) with an intracellular antibiotic resistance trait, a private good (hygromycin phosphotransferase). In pairwise competitions, tomatinase-deficient nuclei gained advantage when rare against a constitutive producer, both in vitro and in planta, even though producers drive lesion expansion. An ordinary differential equation model fitted to the competition outcomes identified antibiotic gradients as the key driver of frequency-dependent selection and predicted stable coexistence of producer and non-producer nuclei across multinucleate bottlenecks. Cheating within fungal syncytia can therefore decouple virulence from reproduction and buffer the selection on antifungal resistance.

genetics↗

bioRxiv2020

Somatic deficiency causes reproductive parasitism in a fungus

Some multicellular organisms can fuse because mergers potentially provide mutual benefits. However, experimental evolution in the fungus Neurospora crassa has demonstrated that free fusion of mycelia favours cheater lineages, but the mechanism and evolutionary dynamics of dishonest exploitation are unknown. Here we show, paradoxically, that all convergently evolved cheater lineages have similar fusion deficiencies. These mutants are unable to initiate fusion but retain access to wild-type mycelia that fuse with them. This asymmetry reduces cheater-mutant contributions to somatic substrate-bound hyphal networks, but increases representation of their nuclei in the aerial reproductive hyphae. Cheaters only benefit when relatively rare and likely impose genetic load reminiscent of germline senescence. We show that the consequences of somatic fusion can be unequally distributed among fusion partners, with the passive non-fusing partner profiting more. We discuss how our findings may relate to the extensive variation in fusion frequency of fungi found in nature.

evolutionary biology↗

bioRxiv2020

The Enterprise: A massive transposon carrying Spok meiotic drive genes

The genomes of eukaryotes are full of parasitic sequences known as transposable elements (TEs). Most TEs studied to date are relatively small (50 - 12000 bp), but can contribute to very large proportions of genomes. Here we report the discovery of a giant tyrosine-recombinase-mobilized DNA transposon, Enterprise, from the model fungus Podospora anserina. Previously, we described a large genomic feature called the Spok block which is notable due to the presence of meiotic drive genes of the Spok gene family. The Spok block ranges from 110 kb to 247 kb and can be present in at least four different genomic locations within P. anserina, despite what is an otherwise highly conserved genome structure. We have determined that the reason for its varying positions is that the Spok block is not only capable of meiotic drive, but is also capable of transposition. More precisely, the Spok block represents a unique case where the Enterprise has captured the Spoks, thereby parasitizing a resident genomic parasite to become a genomic hyperparasite. Furthermore, we demonstrate that Enterprise (without the Spoks) is found in other fungal lineages, where it can be as large as 70 kb. Lastly, we provide experimental evidence that the Spok block is deleterious, with detrimental effects on spore production in strains which carry it. In contrast to the selfish role of the Enterprise in P. anserina, we hypothesize that the mobility of the Enterprise may also play an adaptive role in fungi when Enterprise undergoes horizontal transfer while carrying metabolic genes. This union of meiotic drivers and a transposon has created a selfish element of impressive size in Podospora, challenging our perception of how TEs influence genome evolution and broadening the horizons in terms of what the upper limit of transposition may be.

genomics↗

bioRxiv2019

Combinations of Spok genes create multiple meiotic drivers in Podospora

Meiotic drive is the preferential transmission of a particular allele at a given locus during sexual reproduction. The phenomenon is observed as spore killing in a variety of fungal lineages, including Podospora. In natural populations of Podospora anserina, seven spore killers (Psks) have been identified through classical genetic analyses. Here we show that the Spok gene family underlie the Psk spore killers. The combination of the various Spok genes at different chromosomal locations defines the spore killers and creates a killing hierarchy within the same population. We identify two novel Spok homologs that are located within a complex region (the Spok block) that reside in different chromosomal locations in given natural strains. We confirm that the individual SPOK proteins perform both the killing and resistance functions and show that these activities are dependent on distinct domains, a nuclease and a kinase domain respectively. Genomic data and phylogenetic analysis across ascomycetes suggest that the Spok genes disperse via cross-species transfer, and evolve by duplication and diversification within several lineages.

genetics↗