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PubMed2025

Comparative transcriptomics uncovers poplar and fungal genetic determinants of ectomycorrhizal compatibility.

Ectomycorrhizal symbiosis supports tree growth and is crucial for nutrient cycling and temperate and boreal ecosystems functioning. The establishment of functional ectomycorrhiza (ECM) first requires the association of compatible partners. However, host and fungal genetic determinants governing mycorrhizal compatibility are unknown. To identify such factors in poplar and its fungal associates, we mined existing and de novo tree and fungal transcriptional datasets. We identified co-expressed genes enabling ECM symbiosis at early and mature stages of the interaction. These sets of genes can be divided into general fungal-sensing and ECM-specific components. We highlight the importance of fungal modulation of plant JA-related defenses and the regulation of secretory pathways for ECM compatibility, including upregulation of key fungal small secreted proteins, the downregulation of plant secreted peroxidases, and the downregulation of plant cell wall remodeling proteins concomitantly with the upregulation of fungal glycosyl hydrolases acting on pectin. Not only gene regulation, but also its temporal scale and dynamics seem to play a crucial role for mycorrhizal compatibility. The expression profile of the host Common Symbiosis Pathway and nutrient transporters was also studied, revealing constitutive levels of expression and moderate upregulation in compatible ECM interactions. Overall, these results underscore the importance of novel biological functions during the establishment of ECM symbiosis, help us gain insights into the molecular events determining mycorrhiza compatibility, and serve as a data-rich transcriptomic resource to open new research questions in the field.

Mycorrhizae↗
PubMed2026

Boreal and subarctic freshwaters harbour a diversity of jumbophages.

Bacteriophages (phages) are major drivers of microbial evolution and ecology, yet their diversity and functional roles remain poorly characterized in many natural environments, such as in freshwater systems. In boreal and subarctic freshwater habitats, where bacteria are typically slow-growing and nutrient-limited, phages are predicted to have a critical role in host regulation and horizontal gene exchange. However, only a few isolates have been obtained from such environments, leaving the genetic and functional diversity of these phages largely unexplored. Here, we present a collection of 40 bacteriophages isolated from boreal lakes and rivers using a set of diverse freshwater bacterial hosts. Despite using conventional isolation methods, eight of the isolates possess genomes larger than 200 kilobases and are classified as jumbophages. All jumbophages exhibited myovirus morphology and comparatively slow infection dynamics. These jumbophages include the first known representatives infecting members of Janthinobacterium and Herbaspirillum. Comparative genomic and phylogenetic analyses show that nearly all genomes are distinct from previously described phages, indicating substantial novelty. Diverse auxiliary metabolic and anti-defence systems were identified, including putative NAD+ salvage and acyl carrier protein modules, along with predicted Anti-Thoeris and Anti-CBASS elements. The Pseudomonas-infecting jumbophage Ahti encoded homologues of all 21 core genes that define the nucleus-forming family Chimalliviridae. Additionally, Ahti displayed compartmentalization of DNA during infection, establishing it as the first freshwater nucleus-forming phage. These findings expand our understanding of the ecological, genomic, and functional diversity of phages in boreal environments and highlight the role of freshwater ecosystems as significant reservoirs of novel viral lineages.

anti-defence systems↗
PubMed2025

Genome sequence analysis provides evidence that a boreal crustacean colonised Svalbard well before the ongoing Atlantification of the Arctic.

The study of present-day species distributions often raises questions about historical demography. A particularly interesting phenomenon to put in historical context is contemporary human-induced atlantification and its role in reshaping Arctic ecosystems. Despite this, the colonisation history of the Arctic remains generally understudied. In this study, we investigated the demographic history of the northern acorn barnacle, Semibalanus balanoides, a typically boreal species on the Svalbard Archipelago. Our focus was to determine the source and timing of its colonisation of this Arctic archipelago. Using low-coverage whole-genome sequence data, we evaluated two competing hypotheses: whether S. balanoides populations colonised Svalbard through ancient natural processes before the Anthropocene, or if their appearance is more recent, either natural or a consequence of growing anthropogenic influences, such as increased connectivity and global warming. Our results suggest that this boreal species expanded into the Arctic during the later phase of the Holocene Thermal Optimum, well before human-induced climate change.

Animals↗