Biology subjects

Ridgway, A. M.

Publications and source records attributed to Ridgway, A. M..

4 recordsLinked to original sources

bioRxiv2025

Hypoxia-activated fluorescent probes as markers of oxygen levels in plant cells and tissues

O_LILow oxygen signalling in plants is important in development and stress responses. Measurement of oxygen levels in plant cells and tissues is hampered by a lack of chemical tools with which to reliably detect and quantify endogenous oxygen availability. We have exploited hypoxia-activated fluorescent probes to visualise low oxygen (hypoxia) in plant cells and tissues. C_LIO_LIWe applied 4-nitrobenzyl (4NB-) resorufin and methyl-indolequinone (MeIQ-) resorufin to Arabidopsis thaliana whole cells and seedlings exposed to hypoxia (1% O2) and normoxia (21% O2). Confocal microscopy and fluorescence intensity measurements were used to visualise regions of resorufin fluorescence. C_LIO_LIBoth probes enter A.thaliana whole cells and are activated to fluoresce selectively in hypoxic conditions. Similarly, incubation with A.thaliana seedlings resulted in hypoxia-dependent activation of both probes and observation of fluorescence in hypoxic roots and leaf tissue. MeIQ-Resorufin was used to visualise endogenous hypoxia in lateral root primordia of normoxic A.thaliana seedlings. C_LIO_LIOxygen measurement in plants until now has relied on invasive probes or genetic manipulation. Use of these chemical probes to detect applied and endogenous hypoxia has the potential to facilitate a greater understanding of oxygen dynamics in plant cells and tissues, allowing correlation of oxygen concentrations with adaptive and developmental responses to hypoxia. C_LI

plant biology↗

bioRxiv2024

Rewired gene interactions during development of serially homologous appendages in male and female Drosophila

Drosophila ventral appendages are considered to be serially homologous derived from a ventral appendage ground state and shaped by different Hox inputs. In the legs and antennae a combination of the transcription factors C15, LIM1 homeobox 1 (Lim1), and Al (Aristaless) is required for the development of the tarsal claws and aristae, respectively. However, the roles of these factors in genital development have remained unexplored. Here, we investigated the expression and function of C15, Lim1, and Al in the development of male and female terminalia (genitalia and analia). We found that C15 plays distinct roles in males and females, repressing male clasper bristle formation while promoting bristle development in the female epiproct. Unlike in the antennal and leg discs, C15, Lim1, and Al are not all simultaneously co-expressed in any anal or genital structures in either sex, indicating that the interactions among these factors have diverged across these appendages. Nevertheless, we inferred regulatory interactions between C15 and other factors, reflecting similarities between leg and male clasper development. Finally, we identified a male-specific C15 enhancer that is active in male claspers but not in the female epiproct, legs or antennae. This C15 enhancer modularity may underpin tissue- and sex-specific regulatory logic.

developmental biology↗

bioRxiv2023

Sox21b underlies the rapid diversification of a novel male genital structure between Drosophila species

The emergence and subsequent diversification of morphological novelties is a major feature of animal evolution1-9. However, in most cases little is known about the molecular basis of the evolution of novel structures and the genetic mechanisms underlying their diversification. The epandrial posterior lobes of the male genital arch is a novelty of some species of the Drosophila melanogaster subgroup10-13. The posterior lobes grasp the ovipositor of the female and then integrate between her abdominal tergites, and therefore these structures are important for copulation and species-recognition10-12,14-17. The posterior lobes evolved from co-option of a Hox regulated gene network from the posterior spiracles10 and have since diversified in shape and size in the D. simulans clade in particular over the last 240,000 years driven by sexual selection18-21. The genetic basis of this diversification is highly polygenic but to the best of our knowledge none of the causative genes have yet been identified despite extensive mapping22-30. Identifying the genes underlying the diversification of these secondary sexual structures is essential to understanding the basis of changes in their morphology and the evolutionary impact on copulation and species recognition. Here, we show that the transcription factor encoded by Sox21b negatively regulates posterior lobe size during development. This is consistent with higher and expanded expression of Sox21b in D. mauritiana, which develops smaller posterior lobes compared to D. simulans. We tested this by generating reciprocal hemizygotes and confirmed that changes in Sox21b underlie posterior lobe evolution between these two species. Furthermore, we found that differences in posterior lobe size caused by the species-specific allele of Sox21b significantly affect the duration of copulation. Taken together, our study reveals the genetic basis for the sexual selection driven diversification of a novel morphological structure and its functional impact on copulatory behaviour. HighlightsO_LISox21b regulates the development of the epandrial posterior lobes, a recently evolved novel structure of some species of the Drosophila melanogaster subgroup, which has subsequently rapidly diversified in size and shape. C_LIO_LID. mauritiana has smaller posterior lobes than D. simulans and more expansive expression of Sox21b in the developing genitalia. Using a reciprocal hemizygosity test, we show that variation in Sox21b underlies the diversification of epandrial posterior lobe size and shape between D. simulans and D. mauritiana. C_LIO_LIBehavioural tests show that the species allele of Sox21b causes differences in the duration of copulation in otherwise genetically identical backgrounds. C_LIO_LISox21b has evolved between D. simulans and D. mauritiana, and contributed to the divergence of a morphological novelty and copulatory behaviour between these two species. C_LI

evolutionary biology↗

bioRxiv2020

Unravelling the genetic basis for the rapid diversification of male genital structures between Drosophila species

In the last 240,000 years, males of the Drosophila simulans species clade have evolved striking differences in the morphology of their epandrial posterior lobes and claspers (surstyli). These changes have most likely been driven by sexual selection and mapping studies indicate a highly polygenic and generally additive genetic basis. However, we have limited understanding of the gene regulatory networks that control the development of genital structures and how they evolved to result in this rapid phenotypic diversification. Here, we used new D. simulans / D. mauritiana introgression lines on chromosome 3L to generate higher resolution maps of posterior lobe and clasper differences between these species. We then carried out RNA-seq on the developing genitalia of both species to identify the genes expressed during this process and those that are differentially expressed between the two species. This allowed us to test the function of expressed positional candidates during genital development in D. melanogaster. We identified several new genes involved in the development and possibly the evolution of these genital structures, including the transcription factors Hairy and Grunge. Furthermore, we discovered that during clasper development Hairy negatively regulates tartan, a gene known to contribute to divergence in clasper morphology. Taken together our results provide new insights into the regulation of genital development and how this evolves between species.

evolutionary biology↗