The evolution of parasitic sex ratio distortion
Lead Research Organisation:
University of Liverpool
Department Name: Sch of Biological Sciences
Abstract
Host-parasite interactions are pervasive throughout the natural world, forming a critical component of plant and animal communities. Among them, parasites that distort host sex ratios are widespread in invertebrates. The effect of sex ratio distorters can have a powerful effect on biodiversity; they can cause populations to become extinct and change the composition of animals in the community. Additionally as they can affect harmful as well as beneficial hosts, there is currently a great deal of interest in the use of such parasites for biological control. Sex ratio distortion has evolved in diverse parasites (eukaryotes and bacteria) and affects diverse hosts. Why distort sex ratio? These parasites are passed from mother to offspring in the eggs and are only transmitted by females. These parasites have evolved a number of strategies to increase the relative frequency of female hosts (so increasing the spread of the parasite). Feminisation is induced by the bacterium Wolbachia and by microsporidia (eukaryotic parasites) in Crustacea. In contrast Wolbachia causes male killing in insects. Discovering the mechanisms of male killing and feminisation is key to understanding host-parasite coevolution. We propose that these intracellular parasites are most likely to act by secreting molecules into the host cell which will then influence host molecular pathways, they may modify the response to external hormonal signals or even induce programmed cell death (apoptosis). Such changes could disrupt patterns of sexual development or lead to sex-specific embryo mortality. AIMS: We will investigate the evolution of sex ratio distortion in distantly related parasites by testing the hypotheses that - Similar mechanisms lead to contrasting strategies of sexual manipulation by Wolbachia (male killing in insect hosts, feminisation in crustacean hosts) - Parallel mechanisms of feminisation have evolved in distantly related parasites (Wolbachia and microsporidia) OBJECTIVES I. WE WILL INVESTIGATE THE MOLECULAR BASIS OF WOLBACHIA INDUCED MALE KILLING AND FEMINISATION. We will use state of the art techniques (proteomics) to identify molecules secreted into the host cytoplasm that cause feminisation or male killing, and to follow the changes they induce in the host. We will study this initially in the Drosophila (fruit fly)/Wolbachia male killing system. The genome of both these organisms is known and will help us to identify proteins and their function. We will then go on to study feminising Wolbachia in the crustacean Armadillidium vulgare (woodlouse). II. WE WILL INVESTIGATE THE CELLULAR BASIS OF WOLBACHIA AND MICROSPORIDIA INDUCED FEMINISATION BY TESTING FOR MANIPULATION OF THE PATTERN OF CELL DEATH IN THE DEVELOPING HOST Parasites cause feminisation in Crustacea by inhibiting development of the androgenic gland (the gland that controls male sexual differentiation). To pinpoint the site of action, we will map the distribution of feminising microsporidia and Wolbachia during sexual differentiation of their crustacean hosts. We have recently observed an association between male killing in Drosophila bifasciata by Wolbachia and apoptosis (programmed cell death). We will test whether feminising parasites also induce apoptosis in the androgenic gland in order to feminise the host.
Organisations
People |
ORCID iD |
Alison Dunn (Principal Investigator) | |
Gregory Hurst (Co-Investigator) |
Publications
Dubuffet A
(2013)
Specific detection and localization of microsporidian parasites in invertebrate hosts by using in situ hybridization.
in Applied and environmental microbiology
Dunn AM
(2009)
Parasites and biological invasions.
in Advances in parasitology
Ironside JE
(2011)
Should sex-ratio distorting parasites abandon horizontal transmission?
in BMC evolutionary biology
Jahnke M
(2013)
Effects of feminizing microsporidia on the masculinizing function of the androgenic gland in Gammarus duebeni.
in Journal of invertebrate pathology
Smith JE
(2009)
The ecology and evolution of microsporidian parasites.
in Parasitology
Stentiford GD
(2011)
Hepatospora eriocheir (Wang and Chen, 2007) gen. et comb. nov. infecting invasive Chinese mitten crabs (Eriocheir sinensis) in Europe.
in Journal of invertebrate pathology
Stentiford GD
(2013)
Microsporidia: diverse, dynamic, and emergent pathogens in aquatic systems.
in Trends in parasitology
Tompkins DM
(2011)
Wildlife diseases: from individuals to ecosystems.
in The Journal of animal ecology
Description | joint grant. see outputs for NE D11000/1 and NE /Do12937/1 1. microsporidian sex ratio distorters act by inhibition of androgenic gland function in the host 2. development and testing of in situ hybridisation probes for microsporidian parasites 3. Illustration of importance of parasitic disease for wildlife ecology 4. illustration that microsporidia are emergent pathogens in aquatic ecosystems See NE/D011000/1 for outputs |
Exploitation Route | see NE Do11000/1 |
Sectors | Environment |