Biology subjects

Power, S.

Publications and source records attributed to Power, S..

8 recordsLinked to original sources

bioRxiv2026

Nutrient enrichment and herbivore exclusion disrupt the climate-driven balance between C3 and C4 plants in grasslands

The distribution of plants with different photosynthetic pathways is strongly structured by climate, with C3 plants favoured in cooler temperate regions and C4 plants in hotter, high-light conditions. The relative abundance of C3 and C4 plants across the world has cascading impacts on local food webs, decomposition, productivity and other vital ecosystem processes. Human impacts, including climate change, changes to herbivore assemblages, and increased nutrient availability, are shifting the optimal conditions for important C3 and C4-dominated ecosystems and crops. Using 3,184 plot-level observations from 112 sites across six continents, we reveal how chronic nutrient enrichment disrupts the climate-driven balance between C3 and C4 plants in grasslands. We found that, consistent with expectations, the global distribution of C4 plants was strongly related to climate. However, experimental nutrient addition reduced the relative cover of C4 species, with the strongest declines found when nitrogen and phosphorus were added together. Herbivore exclusion had no consistent effect on C4 plants. Our results provide global experimental evidence that elevated nutrients, particularly nitrogen, alter competitive outcomes among plant functional types to suppress C4 grasses, even in climatically optimal conditions. This has major implications for predicting vegetation responses to global change, with consequences for carbon cycling, primary productivity, herbivore dynamics, and food security.

ecology↗

bioRxiv2026

Distinct forms of dopamine transmission control locomotion and learning

The neuromodulator dopamine is essential for voluntary movement and learning from experience. While these behaviors often occur simultaneously and rely on overlapping nigrostriatal dopamine circuits, they are also separable and can manifest independently. How a single neuromodulatory system controls such disparate aspects of behavior in parallel remains poorly understood. Here we show that striatal dopamine is released through two spatially and functionally distinct modes that are independently regulated and serve distinct behavioral roles. Eliminating dopamine release underlying bulk extracellular accumulation reveals a spatially restricted mode of transmission that maintains phasic dopamine receptor activation on striatal projection neurons. We find that selective loss of diffuse dopamine impairs striatal circuit excitability and reduces locomotion, while point-to-point transmission is sufficient to maintain striatal spine density and support motor and associative learning. We propose that the geometry of dopamine release determines its behavioral output, a principle that explains the breadth of dopamines functions and more broadly elucidates how neurons multiplex different forms of information.

neuroscience↗

bioRxiv2026

Lack of co-ordination of stomatal, hydraulic and leaf browning traits in 16 perennial Australian grass species of differing climate origins

Grasslands are vulnerable to increasing drought with global warming, but process-based models lack the mechanistic knowledge required to predict the magnitude of drought impacts. While a plant hydraulics framework has been successful in advancing process understanding of drought responses in trees, and how drought responses vary across rainfall gradients, similar approaches have rarely been applied to grasses. Here, we quantified the progression of key drought response processes in sixteen dominant perennial grasses (seven C3 and nine C4) with differing climatic origins across eastern Australia. We found that stomatal closure, hydraulic impairment and leaf browning occurred concurrently, in contrast to the progressive sequence typically observed in trees. We also found that drought response traits were not correlated with species climate of origin. The early impairment of leaf hydraulic conductance and leaf browning along with the lack of correlation with climate of origin suggest that grasses may employ fundamentally different strategies to adapt to low water availability than trees. These results highlight the need for grass-specific parameterization of drought responses in process-based models.

ecology↗

bioRxiv2025

Comparative Genomics Reveals Deep Conservation and Lineage-specific Evolution of Mammalian microRNAs

microRNAs (miRNAs) are central post-transcriptional regulators that shape cellular functions, development, and phenotypic diversity. Yet their evolutionary history in mammals remains poorly resolved, largely due to incomplete genome-wide annotation and the difficulties in establishing miRNA orthology. Using a homology-based framework paired with genome synteny for orthology assignment, we characterised miRNA families and investigated their evolutionary dynamics across mammals. Compared to Infernal and MirMachine using a consensus pseudo-ground-truth framework, our method demonstrated better sensitivity-specificity balance, allowing divergent miRNA detection while reducing false positives. Analysis of 73 mammalian genomes revealed major miRNA family gains at the ancestral nodes of Eutheria, Marsupialia, and Haplorrhini, contrasted with substantial losses in Eulipotyphla and Scandentia. Copy number evolution was largely conserved across families, with only a few families (e.g., MIR-145, MIR-2285) showing lineage-specific duplication acceleration. Comparative genome microsynteny further resolved orthology for the multi-copy family LET-7, spanning eight deeply conserved syntenic blocks, as well as for 143 individual miRNAs. We showed that most miRNAs are deeply conserved, with the seed region being most constrained, followed by the mature, star, and loop regions. Within the seed region, positions 4-6 displayed higher conservation than other seed positions, consistent with their roles in core target recognition. Ancestral seed-state reconstruction further revealed diverse evolutionary signatures, including ancestral shifts, recurrent substitutions, and homoplasious changes. Collectively, these findings provide an unprecedented comparative overview of mammalian miRNA evolution and create new opportunities to investigate how shifts in miRNA repertoires and sequence features may underlie lineage-specific regulatory and phenotypic diversification.

genomics↗

bioRxiv2024

Nutrient addition in grasslands worldwide reveals proportional plant diversity decline across spatial scales but little change in beta diversity

Nutrient enrichment typically causes local plant diversity declines. A common but untested expectation is that nutrient enrichment also reduces variation in nutrient conditions among localities and selects for a smaller pool of species, causing greater diversity declines at larger than local scales and thus biotic homogenization. Here we apply a framework that links changes in species richness across scales to changes in the numbers of spatially restricted and widespread species for a standardized nutrient addition experiment across 72 grasslands on six continents. Overall, we find proportionally similar species loss at local and larger scales, suggesting similar declines of spatially restricted and widespread species, and no biotic homogenization after 4 years and up to 14 years of treatment. These patterns of diversity changes are generally consistent across species groups. Thus, nutrient enrichment poses threats to plant diversity, including for widespread species that are often critical for ecosystem functions.

ecology↗

bioRxiv2023

Duplications of human longevity-associated genes across placental mammals

Natural selection has shaped a wide range of lifespans across mammals, with a few long-lived species showing negligible signs of ageing. Approaches used to elucidate the genetic mechanisms underlying mammalian longevity usually involve phylogenetic selection tests on candidate genes, analyses of differential gene expression between age cohorts or species, and measuring age-related epigenetic changes. However, the link between gene duplication and evolution of mammalian longevity has not been widely investigated. Here, we explored the association between gene duplication and mammalian lifespan by analysing 287 human longevity-associated genes across 37 placental mammals. We estimated that the expansion rate of these genes is eight times higher than their contraction rate across these 37 species. Using phylogenetic approaches, we identified 43 genes whose duplication levels are significantly correlated with longevity quotients (FDR < 0.05). In particular, strong correlation observed for four genes (CREBBP, PIK3R1, HELLS, FOXM1) appears to be driven mainly by their high duplication levels in two ageing extremists, the naked mole rat (Heterocephalus glaber) and the greater mouse-eared bat (Myotis myotis). Further sequence and expression analyses suggest that the gene PIK3R1 may have undergone a convergent duplication event, whereby the similar region of its coding sequence was independently duplicated multiple times in both of these long-lived species. Collectively, this study identified several candidate genes whose duplications may underlie the extreme longevity in mammals, and highlighted the potential role of gene duplication in the evolution of mammalian long lifespans.

evolutionary biology↗

bioRxiv2023

Comparative genome microsynteny illuminates the fast evolution of nuclear mitochondrial segments (NUMTs) in mammals

The escape of DNA from mitochondria into the nuclear genome (nuclear mitochondrial DNA, NUMT) is an ongoing process. Although pervasively observed in eukaryotic genomes, their evolutionary trajectories in a mammal-wide context are poorly understood. The main challenge lies in the orthology assignment of NUMTs across species due to their fast evolution and chromosomal rearrangements over the past [~]200 million years. To address this issue, we systematically investigated the characteristics of NUMT insertions in 45 mammalian genomes, and established a novel, synteny-based method to accurately predict orthologous NUMTs and ascertain their evolution across mammals. With a series of comparative analyses across taxa, we revealed that NUMTs may originate from non-random regions in mtDNA, tend to locate in transposon-rich and intergenic regions, and unlikely code for functional proteins. Using our synteny-based approach, we leveraged 630 pairwise comparisons of genome-wide microsynteny and predicted the NUMT orthology relationships across 36 mammals. With the phylogenetic patterns of NUMT presence-and-absence across taxa, we constructed the ancestral state of NUMTs given the mammal tree using a coalescent method. We found support on the ancestral node of Fereuungulata within Laurasiatheria, whose subordinal relationships are still controversial. This strongly indicates that NUMT gain-and-loss over evolutionary time provides great insights into mammal evolution. However, we also demonstrated that one should be cautious when using ancestral NUMT trees to infer phylogenetic relationships. This study broadens our knowledge on NUMT insertion and evolution in mammalian genomes and highlights the merit of NUMTs as alternative genetic markers in phylogenetic inference.

evolutionary biology↗

bioRxiv2020

Plasmids shape the diverse accessory resistomes of Escherichia coli ST131

The human gut microbiome includes beneficial, commensal and pathogenic bacteria that possess antimicrobial resistance (AMR) genes that exchange these predominantly through conjugative plasmids. Escherichia coli is a significant component of the gastrointestinal microbiome and is typically non-pathogenic in this niche. In contrast, extra-intestinal pathogenic E. coli (ExPEC) including ST131 may occupy other environments like the urinary tract or bloodstream where they express genes enabling AMR and host cell adhesion like type 1 fimbriae. The extent to which commensal E. coli and uropathogenic ExPEC ST131 share AMR genes remains understudied at a genomic level, and here we examined this using a preterm infant resistome. Here, individual ST131 had small differences in AMR gene content relative to a larger shared resistome. Comparisons with a range of plasmids common in ST131 showed that AMR gene composition was driven by conjugation, recombination and mobile genetic elements. Plasmid pEK499 had extended regions in most ST131 Clade C isolates, and it had evidence of a co-evolutionary signal based on protein-level interactions with chromosomal gene products, as did pEK204 that had a type IV fimbrial pil operon. ST131 possessed extensive diversity of selective type 1, type IV, P and F17-like fimbriae genes that was highest in subclade C2. The structure and composition of AMR genes, plasmids and fimbriae vary widely in ST131 Clade C and this may mediate pathogenicity and infection outcomes. Data SummaryThe following files are available on the FigShare project "Plasmids_ST131_resistome_2020" : O_LI The set of 794 AMR genes derived from [74] are available (with their protein sequence translation) at FigShare at doi: dx.doi.org/10.6084/m9.figshare.11961402. C_LIO_LI The AMR gene profiles per sample determined by their BLAST sequence similarity results against CARD are available at FigShare at doi: dx.doi.org/10.6084/m9.figshare.11961612. This dataset includes the PlasmidFinder results. It also includes other AMR database comparisons (ARG-ANNOT, ResFinder, MegaRes, VFDB and VirulenceFinder). C_LIO_LI The BLAST sequence similarity results for the fim, pil, pap and ucl operons genes versus 4,071 E. coli ST131 assemblies from Decano & Downing (2019) are available at FigShare at doi: dx.doi.org/10.6084/m9.figshare.11961711. C_LIO_LI The genome sequences and annotation files for reference genomes NCTC13441, EC958 and SE15, along with the assembled contigs for 83972 and 3_2_53FAA are available at FigShare at doi: dx.doi.org/10.6084/m9.figshare.11961813. C_LIO_LI The 4,071 E. coli ST131 genome assemblies from Decano & Downing (2019) are available at FigShare at doi: 10.6084/m9.figshare.11962278 (the first 1,680 assemblies) and at doi: dx.doi.org/10.6084/m9.figshare.11962557 (the second 2,391 assemblies). C_LI

genomics↗