Biology subjects

Brown, G. G.

Publications and source records attributed to Brown, G. G..

6 recordsLinked to original sources

bioRxiv2026

Systematic evidence map of research on life-history traits in native and introduced earthworms

Invasive species constitute one of the most significant threats to biodiversity worldwide, and are responsible for more than $400 billion in losses each year. An organism's life-history strategy, defined by how it allocates resources among growth, survival, and reproduction, plays a central role in determining whether it becomes invasive. While the life-history profiles of aboveground invaders are increasingly well characterised, those of invasive species below ground remain poorly understood. Earthworms are a diverse group of soil invertebrates that can help fill this knowledge gap. Of the ~5,800 earthworm species described to date, nearly 2% are cosmopolitan, meaning they have achieved wide geographic distributions despite limited ability for active dispersal. While life-history traits are likely to contribute to their worldwide distribution, the existing research on earthworm trait variation has not been systematically reviewed. To address this gap, we assessed the taxonomic scope, geographic coverage, and methodologies of studies on earthworm life history traits for species occurring in the US and Brazil, spanning a broad latitudinal range. Our literature search yielded over 8,000 articles across 180 species and revealed that introduced species have received considerably more research attention than native species. Research was concentrated on a few model species, most studies were experimental, and variation in life history traits was most commonly assessed in response to chemical compounds, vermicompost feed type, and environmental factors such as temperature, moisture and soil composition. Variation in adult survival was reported most frequently, followed by adult growth and cocoon production, with the bulk of life history research conducted in India (20%) and China (9%). To better understand the effect invasive earthworm species might have on native fauna, future research on life histories should address taxonomic biases and prioritise detailed study of the life cycles of native species in their natural habitat.

ecology↗

bioRxiv2026

Transcription directs Holliday junction branch migration

During meiosis, genetic diversity arises from the resolution of branched DNA intermediates called Holliday junctions to create crossovers--sites of reciprocal exchange between parental chromosomes. Holliday junctions arise during the repair of Spo11-induced DNA breaks, yet the principles linking break formation, repair, and chromosome architecture remain unclear. Top3, a type IA topoisomerase, acts on Holliday junctions, but its spatiotemporal dynamics are unknown. Here, we map Top3 catalytic activity throughout meiotic prophase with strand specificity and nucleotide resolution. We identify a DNA sequence motif associated with catalysis and a pattern of activity around Spo11 hotspots that requires ongoing repair and Top3s helicase partner, Sgs1. Strikingly, Top3 activity shifts over time, influenced by transcription, cohesin, and the crossover factors Msh5 and Mer3, redistributing toward sites of convergent transcription--known locations of meiotic cohesin association. Upon prophase exit, as crossovers are resolved, Top3 activity subsides. Remarkably, maps of genome-wide recombination reveal that crossover resolution preferentially occurs at these same regions of convergent transcription. Collectively, we propose that Top3 coordinates the transcription-coupled movement of Holliday junctions from Spo11 hotspots towards cohesin-associated axis sites, whereupon crossover resolution occurs to ensure accurate meiotic chromosome segregation.

molecular biology↗

bioRxiv2026

Localised negative feedback shapes genome-wide patterning of meiotic DNA breaks

Genetic diversity within sexually reproducing species arises via the formation and repair of programmed DNA double-strand breaks (DSBs) created by the evolutionarily conserved topoisomerase-like enzyme, Spo11. Because DSBs threaten genome stability, their formation is tightly regulated in both space and time. In S. cerevisiae, Tel1, the orthologue of mammalian Ataxia Telangiectasia Mutated (ATM) kinase, suppresses nearby DSB formation through local inhibition known as DSB interference. However, whether such local inhibition reshapes the genome-wide DSB landscape remains unclear. Here, we develop a quantitative simulation framework to model how Tel1-mediated feedback shapes Spo11-DSB formation across the yeast genome. We demonstrate that innate chromosome-specific DSB patterns, when combined with interference, generate complex, population-level redistribution of DSBs. We define the spatial range over which interference propagates and provide evidence that this regulatory mechanism requires Tel1 recruitment to DSBs via Xrs2 and Tel1 kinase activity. Although the pro-DSB factor Rec114 contributes to DSB regulation, mutation of potential Rec114 phosphorylation sites indicates that it is not an essential target of Tel1. Together, these findings demonstrate how localised negative feedback can drive broad-scale, emergent patterning of a fundamental genome-modifying process, with the potential in meiosis to influence recombination initiation and, consequently, genetic variation across generations.

cell biology↗

bioRxiv2024

A can of worms: estimating the global number of earthworm species

Estimating the overall species number for a given taxon is a central issue in ecology and conservation biology. This is especially topical for soil organisms, which comprise most known species but whose taxonomy remains largely understudied. Here, we estimated the global number of earthworm species based on the Joppa approach, which models taxonomic effort over time to estimate the total number of known and as yet unknown species in a given taxa. Our Bayesian estimation of the Joppa model suggests a global diversity of the order of 30,000 species, suggesting that the 5,679 earthworm taxa already described only represent around 20% of the actual global species diversity. However, the uncertainty around this estimate is considerable due to severe undersampling and as the model cannot unambiguously decide whether we are describing few species because of a small pool of as yet unknown species, or because of a lack of taxonomic efficiency. Considering the current rate of new species description, we calculate that it would take at least 120 years to describe all the earthworm species existing on Earth, and we discuss thedifferent strategies that should be developed to facilitate and accelerate the discovery and naming of species new to science.

ecology↗

bioRxiv2024

The applicability of Regional Red List assessments for soil invertebrates: First assessment of five native earthworm species in Canada

Earthworms (Annelida: Clitellata: Crassiclitellata) are prominent members of the soil community, important to many ecosystem functions. Despite this, and like many other soil invertebrates, they are rarely considered in conservation assessments, including the IUCN Red List assessments used to assess species extinction risk. To investigate the applicability of the IUCN Regional Red Listing protocol to soil invertebrates, we assessed the conservation status of five earthworm species known to be native to Canada using this protocol and all available occurrence records. In Canada, no earthworm species have yet been assessed by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC). Due to the lack of data on population sizes and their trends, all five species were assessed using their Extent of Occurrence (EOO) (Criterion B). One species was assessed as Vulnerable, two were assessed in non-threatened categories, and two were assessed as Data Deficient. For the majority, the main threats identified were the continuing loss of potential habitat due to land conversion and resource exploitation, as well as the effects of climate change. Increasing the amount of data, including but not limited to distribution and habitat preferences, would make the assessment process easier and status decisions better supported. By undertaking regional assessments for five native earthworm species in Canada, we show that Regional Red List assessments are feasible for soil invertebrates.

ecology↗

bioRxiv2020

nMAT3 is an essential maturase splicing factor required for holo-complex I biogenesis and embryo-development in Arabidopsis thaliana plants

Group II introns are large catalytic RNAs that are particularly prevalent in the organelles of terrestrial plants. In angiosperm mitochondria, group II introns reside in the coding-regions of many critical genes, and their excision is essential for respiratory-mediated functions. Canonical group II introns are self-splicing and mobile genetic elements, consisting of the catalytic intron-RNA and its cognate intron-encoded endonuclease factor (i.e. maturase, Pfam-PF01348). Plant organellar introns are extremely degenerate, and lack many regions that are critical for splicing, including their related maturase-ORFs. The high degeneracy of plant mitochondrial introns was accompanied during evolution by the acquisition of host-acting protein cofactors. These include several nuclear encoded maturases (nMATs) and various other splicing-cofactors that belong to a diverse set of RNA-binding families, e.g. RNA helicases (Pfam-PF00910), Mitochondrial Transcription Termination Factors (mTERF, Pfam-PF02536), Plant Organelle RNA Recognition (PORR, Pfam-PF11955), and Pentatricopeptide repeat (PPR, Pfam-PF13812) proteins. Previously, we established the roles of MatR and three nuclear-maturases, nMAT1, nMAT2, and nMAT4, in the splicing of different subsets of mitochondrial introns in Arabidopsis. The function of nMAT3 (AT5G04050) was found to be essential during early embryogenesis. Using a modified embryo-rescue method, we show that nMAT3-knockout plants are strongly affected in the splicing of nad1 introns i1, i3 and i4 in Arabidopsis mitochondria. The embryo-defect phenotype is tightly associated with complex I biogenesis defects. Functional complementation of nMAT3 restored the splicing defects and altered embryogenesis phenotypes associated with the nmat3 mutant-line.

plant biology↗