Biology subjects

Griem-Krey, H.

Publications and source records attributed to Griem-Krey, H..

4 recordsLinked to original sources

bioRxiv2025

Transposable elements hitchhike on Starships across fungal genomes

Horizontal transfer (HT) of transposable elements (TEs) is a widespread phenomenon in eukaryotes and is often associated with bursts of TE activity. This process profoundly influences genome evolution by introducing novel genetic material and driving genetic variation. However, the precise mechanisms facilitating these transfers remain largely uncharacterized. Here, we report a recent TE burst in the insect-pathogenic fungus Metarhizium anisopliae. Our analysis reveals that the actively transposing TEs were introduced via hitchhiking on a so-called Starship--a class of large, themselves horizontally transferable transposons found within the fungal subphylum Pezizomycotina. This particular Starship carried 73 TEs, 43 of which exhibited increased copy numbers in the recipient genome, including 508 perfect copies. This expansion triggered extensive structural reshuffling across all chromosomes and led to the formation of a novel chromosome. Remarkably, this structural reorganization was associated with a dramatic phenotypic shift: the loss of pathogenicity. Expanding our analysis to other fungi, we found that Starship-mediated horizontal transfer of TEs is a general phenomenon. A majority (74%) of 618 published Starships also harbor TEs, which can constitute up to 72% of their content. Moreover, Starships serve as sources of actively transposing TEs: 16% of Starships carried at least one TE with a perfect copy found elsewhere in the genome, and identical TEs were observed on Starships from different species. Collectively, our results establish Starships as major vectors of horizontal TE transfer within Pezizomycotina and further highlight their profound impact on recipient fungal genomes through TE piggybacking.

evolutionary biology↗

bioRxiv2025

The nematode Caenorhabditis elegans can benefit from its coexisting fungal microbiome member Barnettozyma californica

The nematode Caenorhabditis elegans is known to feed on and interact with bacteria in its environment and has become a model organism for microbiome studies. However, whether and how C. elegans interacts with co-occurring fungi remains largely unknown, despite the presence of many fungal species in its natural habitat. Here, we isolate the yeast Barnettozyma californica from a mesocosm experiment with C. elegans and characterize its genome and interaction with the nematode. We find that B. californica is ingested by C. elegans and can serve as a sole, albeit poor, food source. Yet, when present together with Escherichia coli OP50, the fungus can lead to higher population growth and altered foraging behavior, suggesting that this fungi-bacteria mixture provides a better food source than bacteria alone. This effect varied between different natural C. elegans strains, suggesting a genomic basis for the nematodes interaction with B. californica. The fully assembled and annotated genome of the isolated B. californica strain does not indicate any obvious candidate genes for its interaction with C. elegans and/or E. coli OP50. Overall, our results provide an intriguing example of the complexity and multi-level relationship between naturally interacting fungi, bacteria, and animals. Graphical AbstractBarnettozyma californica is a member of the fungal microbiome of the model nematode Caenorhabditis elegans and can serve as food for worms. When combined with E. coli, this fungus can increase population growth and reduce foraging behaviour dependent on C. elegans genotype, revealing a genetic influence on host-fungus-bacterium interactions. O_FIG O_LINKSMALLFIG WIDTH=189 HEIGHT=200 SRC="FIGDIR/small/638710v1_ufig1.gif" ALT="Figure 1"> View larger version (36K): org.highwire.dtl.DTLVardef@184b29eorg.highwire.dtl.DTLVardef@eabb71org.highwire.dtl.DTLVardef@b810ceorg.highwire.dtl.DTLVardef@5745c7_HPS_FORMAT_FIGEXP M_FIG C_FIG

ecology↗

bioRxiv2023

The intricate triangular interaction between protective microbe, pathogen, and host genetics determines fitness of the metaorganism

The microbiota shapes host biology in numerous ways. One example is protection against pathogens, which is likely critical for host fitness in consideration of the ubiquity of pathogens. The host itself can affect abundance of microbiota or pathogens, which has usually been characterised in separate studies. To date, however, it is unclear how the host influences the interaction with both simultaneously and how this triangular interaction determines fitness of the host-microbe assemblage, the so-called metaorganism. To address this current knowledge gap, we focused on a triangular model interaction, consisting of the nematode Caenorhabditis elegans, its immune-protective symbiont Pseudomonas lurida MYb11, and its pathogen Bacillus thuringiensis Bt679. We combined the two microbes with C. elegans mutants with altered immunity and/or microbial colonisation, and found that (i) under pathogen stress, immunocompetence has a larger influence on metaorganism fitness than colonisation with the protective microbe, (ii) in almost all cases, MYb11 still improves fitness, and (iii) disruption of p38 MAPK signalling, which contributes centrally to immunity against Bt679, completely reverses the protective effect of MYb11, which further reduces nematode survival and fitness upon infection with Bt679. Our study highlights the complex interplay between host genetics, protective microbe, and pathogen in shaping metaorganism biology.

evolutionary biology↗

bioRxiv2023

Host and microbiome jointly contribute to adaptation to a complex environment

Most animals and plants have associated microorganisms, collectively referred to as their microbiomes, which can provide essential functions. Given their importance, host-associated microbiomes have the potential to contribute substantially to adaptation of the host-microbiome assemblage (the "metaorganism"). Microbiomes may be especially important for rapid adaptation to novel environments because microbiomes can change more rapidly than host genomes. However, it is not well understood how hosts and microbiomes jointly contribute to metaorganism adaptation. We developed a model system with which to disentangle the contributions of hosts and microbiomes to metaorganism adaptation. We established replicate mesocosms containing the nematode Caenorhabditis elegans co-cultured with microorganisms in a novel complex environment (laboratory compost). After approximately 30 nematode generations (100 days), we harvested worm populations and associated microbiomes, and subjected them to a common garden experiment designed to unravel the impacts of microbiome composition and host genetics on metaorganism adaptation. We observed that adaptation took different trajectories in different mesocosm replicates, with some increasing in fitness and others decreasing, and that interactions between host and microbiome played an important role in these contrasting evolutionary paths. We chose two exemplary mesocosms (one with a fitness increase and one with a decrease) for detailed study. For each example, we identified specific changes in both microbiome composition (for both bacteria and fungi) and nematode gene expression associated with each change in fitness. Our study provides experimental evidence that adaptation to a novel environment can be jointly influenced by host and microbiome.

evolutionary biology↗