Biology subjects

Guy, M.

Publications and source records attributed to Guy, M..

5 recordsLinked to original sources

bioRxiv2026

Bidirectional changes in seabird populations drive terrestrial ecosystem function and biodiversity

Seabird populations fluctuate dramatically in response to perturbations and human activity, such as the current highly pathogenic avian influenza (HPAI) panzootic and fishery practices. Seabirds vector marine nutrients into terrestrial and coastal environments causing cascading effects through ecosystems, but quantifying the inter-related mechanisms underpinning marine-terrestrial cascades in response to changes in seabird populations is challenging. Here we simulate decreases and increases in seabird density, as have occurred due to HPAI and fishing practices respectively, through turf transplant experiments and stratified surveys to quantify marine nutrient cascades and show how they regulate terrestrial ecosystem processes and biodiversity. We use structural equation modelling to quantify the relative strengths of each hypothesised mechanistic pathway in the ecological network. This analysis identified that seabirds shape terrestrial plant and invertebrate biodiversity primarily indirectly, through modifying soil nutrient availability. Our findings highlight the ecosystem changes that are likely occurring, and the pathways through which they operate, due to acute declines and chronic increases in seabirds caused by HPAI, fishing practices or other drivers.

ecology↗

bioRxiv2026

Supporting-like cells constitute an alternative steroidogenic lineage conserved in amniotes

In mammals, the production of sex hormones is widely considered to depend on the interstitial lineage of the gonad, which differentiates into Leydig cells in males or theca cells in females. However, certain mammalian species evidence gonadal steroidogenic activity prior to the specialization of these interstitial lineages, suggesting that alternative cell types may assume this function. Here we reveal a previously unrecognized role for supporting-like cells (SLCs), which can act as a major steroidogenic lineage during mammalian embryonic development. Through comparative single-cell transcriptomics, steroidomics and in toto organ imaging we find that in rabbits, SLCs not only contribute to the formation of gonadal rete structures, as described for other mammals, but also differentiate into a steroid-producing population. The steroidogenic program of SLCs is initially activated in both sexes but selectively maintained in ovaries, whereas in testes it is progressively replaced by that of interstitially derived Leydig cells. Evolutionary comparisons indicate that SLCs may represent an ancestral lineage that is homologous to the steroidogenic cells of non-mammalian species, which also derive from supporting precursors and share expression of cell fate regulators such as PAX2/8 and TBX1. Altogether, our findings redefine current models of gonadal lineages, revealing an unexpected plasticity in sex differentiation and exemplifying how distinct cell types can converge on analogous functions during evolution.

developmental biology↗

bioRxiv2025

Ovarian development is driven by early spatiotemporal priming of the coelomic epithelium

Ovarian organogenesis relies on the coordinated specification of supporting and steroidogenic lineages from multipotent coelomic epithelium (CE) progenitors. However, it remains unclear how ovarian cellular diversity arises and whether CE progenitors are fate-biased before or after ingression into the gonad. We show that CE cells in fetal mouse and human ovaries are transcriptionally heterogeneous and spatially organized into subdomains already primed toward supporting or steroidogenic identities. CE priming is dynamic, influenced by proximity to the mesonephros, with a transient coexistence of both progenitor types before resolution toward a predominantly supporting-biased CE. In mice, delamination of primed CE cells seeds intragonadal niches that generate pre-granulosa and steroidogenic progenitors. We further demonstrate that fetal steroidogenic progenitors give rise to adult stromal and theca cells, and that granulosa cells have a dual origin from CE-derived and supporting-like cells. Together, these findings reveal a conserved, spatially encoded program of ovarian lineage specification.

developmental biology↗

bioRxiv2019

A low-cost and high-precision scanning electrochemical microscope built with open source tools

A low-cost Scanning Electrochemical Microscope (SECM) was built with a 0.6 pA current measurement capability potentiostat and submicron resolution motorized stage, using open source software and hardware tools. The high performance potentiostat with a Python graphical user interface was built based on an open source project. Arduino boards, stepper motors, a manual XY micromanipulator stage, 3D printed couplers and gears were used in building the motorized stage. An open source motor control software was used for moving the motorized stage with high precision. An inverted microscope was utilized for viewing a standard microelectrode while scanning. The setup was tested in the formation of a map of electrochemical signals from an array of pores on a parafilm membrane. As the setup will be used in future biosensing experiments, DNA hybridization detection experiments were also performed with the setup.

biochemistry↗

bioRxiv2018

Epigenetics of floral homeotic genes in relation to sexual dimorphism in the dioecious plant Mercurialis annua

In plants, dioecy characterizes species carrying male and female flowers on separate plants and occurs in about 6% of angiosperms. To date, the molecular mechanism(s) underlying sexual dimorphism is essentially unknown. The ability of gender-reversal by hormone application suggests that epigenetics might play an important role in sexual dimorphism. Proteome analysis of nuclei derived from flower buds of females, males and feminized males of the dioecious plant Mercurialis annua revealed differentially expressed proteins related to nucleic acid binding proteins, hydrolases and transcription factors, including floral homeotic genes. Further analysis showed that class B genes are mainly expressed in male flowers, while class D genes, as well as SUPERMAN-like genes, were mainly expressed in female flowers. Cytokinin-induced feminization of male plants was associated with down-regulation of male-specific genes concomitantly with up-regulation of female-specific genes. No correlation could be found between the expression of class B and D genes and their DNA methylation or chromatin conformation. Thus, our results ruled out epigenetic control over floral identity genes as the major determinants regulating sexual dimorphisms. Rather, determination of sex in M. annua might be controlled upstream of floral identity genes by a gender-specific factor that affects hormonal homeostasis.\n\nHighlightsSex determination in Mercurialis annua is not related to epigenetics of floral homeotic genes but appears to be modulated by an unknown gender-specific regulator(s) that affects hormonal homeostasis.

plant biology↗