Biology subjects

St. Leger, R.

Publications and source records attributed to St. Leger, R..

3 recordsLinked to original sources

bioRxiv2026

Origins and metabolic evolution of multifunctionality in Metarhizium robertsii: linking phenotypic diversity to ecological niche plasticity

This study investigates the evolution of fungi with complex multifunctional ecological roles using early and recently diverged lineages of Metarhizium robertsii as a model. The early diverged strains are characterized by slower insect killing, extensive pre-mortem fungal proliferation within hosts, and prolific sporulation, whereas recently diverged strains show rapid growth, a "kill and consume" strategy linked to destruxin toxin production, and enhanced plant root colonization. Metabolic assays demonstrated that recently diverged strains utilize a broader range of carbon sources, supporting their ecological versatility as pathogens, endophytes, and saprophytes. Germination rates on insect cuticles and plant roots strongly correlate with each other, and with virulence to Drosophila and beetles (Tenebrio molitor, Popillia japonica), highlighting nutritional flexibility as a key driver of ecological adaptation. Immune response assays in Drosophila revealed that virulence differences among strains are also partly mediated by host immune activation. These findings suggest that nutritional mode shifts underpin the evolutionary trajectory from specialist insect pathogen to plant associations and enhanced insect virulence within M. robertsii, providing a valuable model for studying fungal ecological plasticity and informing the development of fungal biofertilizers and biopesticides.

evolutionary biology↗

bioRxiv2025

The effects of sleep disruption, sex, and mating status on susceptibility to fungal (Metarhizium anisopliae) infections in Drosophila melanogaster

Important biological functions, including host defense, are linked to circadian rhythm and sleep. Studies have also indicated that the sex of the host can alter disease processes. In this study, we used a genetic approach in Drosophila to determine how sleep interacts with sex to influence the outcomes of infection with Metarhizium anisopliae strain Ma549. We found that as in mammals, Drosophila slept more after infection. The sleep-deprived Drosophila Shaker mutant with intact circadian rhythms failed to show this increased sleep response (sickness sleep) and succumbed quickly to infection. Mutants with disrupted PERIOD (PER) or CLOCK (CLK) affect circadian rhythms. The per01mutant shifted day/night cycles but not total sleep amounts, whereas the ClkJrkmutant reduced sleep duration. Although mutations in per or Clk both impair sickness sleep, only per protects against disease, whereas active Clk reduces survival in infected Drosophila, which we attribute to it being pleiotropic. Independent of mutant status, males slept more than females, and virgins slept more than mated flies and survived infection longer, indicating that sex and mating status influence sleep and disease resistance irrespective of circadian rhythms.

microbiology↗

bioRxiv2025

Could malaria mosquitoes be controlled by periodic releases of transgenic mosquitocidal Metarhizium pingshaense fungus? A mathematical modeling approach

Insect pathogenic fungi offer a promising alternative to chemical insecticides for controlling insecticide resistant mosquitoes. One proposed method involves releasing male Anopheles mosquitoes contaminated with transgenic Metarhizium pingshaense (Met-Hybrid), to lethally infecting females during mating. This study presents a novel deterministic mathematical model to evaluate the impact of this control approach in malaria-endemic areas. The model incorporates two fungus transmission pathways: mating-based transmission and indirect transmission through contact with fungus-colonized mosquito cadavers. We found the fungus cannot establish in the mosquito population without transmission from infected cadavers (in this scenario, the reproduction number of the model is zero). However, if transmission from colonized cadavers is possible, the fungus can persist in the local mosquito population when the reproduction number exceeds one. Simulations of periodic releases of infected male mosquitoes, parameterized using Met-Hybrid-exposed mosquito data from Burkina Faso, show that an 86% reduction in the local female mosquito population can be achieved by releasing 10 Met-Hybrid-exposed male mosquitoes per wild mosquito every three days over six months. This matches the efficiency of some genetic mosquito control approaches. However, a 90% reduction in the wild mosquito population requires, for instance, daily releases of the fungal-treated mosquitoes in a 6:1 ratio for about 5 months, proving less efficient than some genetic approaches. This study concludes that fungal programs with periodic releases of infected males may complement other methods or serve as an alternative to genetic-based mosquito control methods, where regulatory, ethical, or public acceptance concerns restrict genetically-modified mosquito releases.

ecology↗