Biology subjects

Field, K.

Publications and source records attributed to Field, K..

6 recordsLinked to original sources

bioRxiv2026

Protocells reproduce morphological and chemical signatures of early microfossils

Identification of early microfossils relies on morphological and chemical criteria assumed to be unique to life, but whether abiotic microstructures can satisfy these criteria has not been rigorously tested. Hydrothermal environments preserve microfossils but are also efficient geochemical reactors for abiotic reactions. Protocells form in hydrothermal conditions and represent a plausible abiotic analogue to early microfossils. Here we show that protocells form from simple organic molecules in low-temperature, alkaline hydrothermal conditions in the presence of silica and produce spheres, filaments, and lenticular structures that strongly resemble the morphology of purported microfossils in Archaean silica cherts. FTIR spectroscopy provides overlapping chemical signatures across protocells, microorganisms, and geologic microstructures. In addition, the FTIR R3/2 ratio, a chemometric index often used to discriminate domains and determine biogenicity, identifies eight different protocell systems as either bacterial, archaeal, or eukaryotic. These data suggest that protocells preserved in ancient hydrothermal deposits can satisfy current biogenicity criteria, undermining the reliability of interpretations of the early fossil record. As life detection is the primary objective for current space exploration endeavours, robust biogenicity protocols that account for abiotic signatures are essential.

paleontology↗

bioRxiv2025

PHO2 suppresses arbuscular mycorrhizal symbiosis in high phosphate conditions

Arbuscular mycorrhizal (AM) symbiosis is an ancient relationship formed between most plants and Glomeromycotina fungi, typically in response to phosphate (Pi) limitation in soils. By hosting these fungi in their roots, plants extend their access to essential mineral nutrients and water beyond the rhizosphere, while providing the fungus with carbon in return. This mutualistic symbiosis presents a promising tool for enhancing sustainability in agriculture, as it not only supports plant nutrition but also immunity and wider soil health. However, achieving high crop yields currently relies on supplementing plants with excess Pi, which suppresses AM symbiosis. We found that this suppression is mediated by a key negative regulator of the Pi starvation response (PSR) in rice (Oryza sativa), Phosphate overaccumulator 2 (PHO2). PHO2 encodes an E2 ubiquitin-conjugating enzyme which targets various proteins involved in the PSR in Pi-sufficient conditions for protein degradation. Here we report that pho2 mutants of rice and Nicotiana benthamiana retained high AM fungal colonisation even in high Pi conditions. Our transcriptomic analysis of uninoculated rice roots revealed that pho2 mutants are less sensitive to Pi treatment and retain susceptibility to AM symbiosis by maintaining expression of a core set of AM-related genes gating the early stage AM fungal entry, such as genes involved in strigolactone biosynthesis, LysM-containing plant receptors for fungal molecules, and components of the common symbiosis signalling pathway (CSSP). Furthermore, isotope tracing using 33P and phosphate transporter (PHT1) gene expression patterns collectively suggest enhanced direct and symbiotic Pi overaccumulation in pho2 mutant leaves. Together, our data reveal a new role for PHO2, as a negative regulator of AM colonisation and symbiotic Pi accumulation in shoots.

plant biology↗

bioRxiv2025

Common symbiotic signalling pathway not essential for formation of functional mutualisms with endophytic fungi

Most plants form mutualistic symbioses with soil fungi, including arbuscular mycorrhizal (AM) fungi. These fungi usually transfer soil nutrients to plants and assimilate carbon from host plant photosynthesis. Recently, Mucoromycotina fine root endophytes (MFRE) were identified as nutritionally mutualistic and widespread fungal symbionts of plants, establishing MFRE as a new class of mycorrhizal fungi. However, the regulatory mechanisms for MFRE symbioses are completely unknown. Other symbionts, like AM fungi, use the Common Symbiotic Signalling Pathway (CSSP) to establish symbiosis. To explore whether MFRE interactions also involve this pathway, we cultured MFRE with CSSP mutants of Medicago truncatula which show impaired AM symbioses and tracked carbon and nutrient transfers using isotope tracers. Results show no differences in root colonization or nutrient exchange, suggesting MFRE symbioses are regulated by different molecular mechanisms. This finding highlights the unique nature of MFRE symbiosis, broadening our understanding of diverse fungal symbioses and their evolutionary significance.

microbiology↗

bioRxiv2024

White adipose tissue remodeling in Little Brown Myotis (Myotis lucifugus) with white-nose syndrome

White-nose syndrome (WNS) is a fungal wildlife disease of bats that has caused precipitous declines in certain Nearctic bat species. A key driver of mortality is premature exhaustion of fat reserves, primarily white adipose tissue (WAT), that bats rely on to meet their metabolic needs during winter. However, the pathophysiological and metabolic effects of WNS have remained ill-defined. To elucidate metabolic mechanisms associated with WNS mortality, we infected a WNS susceptible species, the Little Brown Myotis (Myotis lucifugus), with Pseudogymnoascus destructans (Pd) and collected WAT biopsies for histology and targeted lipidomics. These results were compared to the WNS-resistant Big Brown Bat (Eptesicus fuscus). A similar distribution in broad lipid class was observed in both species, with [~]60% of total WAT consisting of triacylglycerides (TAGs). We found several baseline differences in WAT chemical composition between species. M. lucifugus WAT had significantly higher levels of measured TAGs ([~]30%). Higher lipid levels in E. fuscus WAT were primarily sphingomyelins and glycerophosphoethanolamines (PEs), along with glycerophospholipids (GPs) dominated by unsaturated or monounsaturated moieties and n-6 (18:2, 20:2, 20:3, 20:4) fatty acids. These differences between M. lucifugus and E. fuscus may indicate dietary differences that lead to differential "fuel" reserves that are available during torpor. Following Pd-infection, we found that perturbation to WAT reserves occurs in M. lucifugus, but not in the resistant E. fuscus. A total of 36 GPs (primarily PEs) were higher in Pd-infected M. lucifugus, indicating perturbation to the WAT structural component. In addition to changes in lipid chemistry, smaller adipocyte sizes and increased extracellular matrix deposition was observed in Pd-infected M. lucifugus. This is the first study to describe WAT lipidomic composition of bats with different susceptibilities to WNS and highlights that recovery from WNS may require repair from adipose remodeling in addition to replenishing depot fat during spring emergence.

biochemistry↗

bioRxiv2023

Signals of positive selection in Palearctic bat species coexisting with a fungal pathogen

Traits that directly influence the survival of an organism are suspect to positive selection. Disease can act as a driving force in shaping the genetic makeup across populations, even species, if the impacts are influencing a particularly sensitive part of their life cycles. White-nose syndrome is a fungal disease that affects bats during hibernation. The mycosis has caused massive population declines of susceptible species in North America, whereas in Eurasia, where the fungal pathogen has coevolved with its hosts for an extended period of time, bats appear to tolerate infection. Here, we adopted both whole-genome sequencing approaches and a literature search to compile a set of 300 genes from which to investigate for signals of positive selection in genomes of 11 Eurasian bats at the codon-level. Our results indicate significant positive selection in 38 genes, many of which have a marked role in responses to infection. Our findings suggest the fungal disease known as white-nose syndrome may have applied a significant selective pressure on hibernatory Eurasian Myotis-bats in the past, which can partially explain their survival in the presence of the pathogen.

evolutionary biology↗

bioRxiv2021

A soil-binding polysaccharide complex released from root hairs functions in rhizosheath formation

To elucidate factors involved in rhizosheath formation, wild type (WT) barley (Hordeum vulgare L. cv. Pallas) and a root hairless mutant, bald root barley (brb), were investigated with a combination of physiological, biochemical and immunochemical assays. When grown in soil, WT barley roots bound [~]5-fold more soil than brb per unit root length. High molecular weight (HMW) polysaccharide exudates of brb roots had less soil-binding capacity than those of WT root exudates. Carbohydrate and glycan monoclonal antibody analyses of HMW polysaccharide exudates indicated differing glycan profiles. Relative to WT plants, root exudates of brb had reduced signals for arabinogalactan-protein (AGP), extensin and heteroxylan epitopes than brb. In contrast, the brb root exudate contained [~]25-fold more detectable xyloglucan epitope relative to WT. Epitope detection chromatography indicated that the increased detection of xyloglucan in brb exudates was due to enhanced abundance of a neutral polymer. Exudate preparations from brb had decreased amounts of an acidic form of xyloglucan associated with root-hair located glycoprotein and heteroxylan epitopes and with soil-binding properties. Therefore, in addition to physically structuring soil particles, root hairs facilitate rhizosheath formation by releasing a soil-binding polysaccharide complex. One sentence summaryThe root exudate of a root hairless mutant of barley, relative to wild type, has an altered pattern of polysaccharide epitopes and lesser amounts of an acidic soil-binding polysaccharide complex.

plant biology↗