Date : 17/04/2009
Evolution of Nematode Development
Institut Jacques Monod,
UMR7592, CNRS-Université Paris-Diderot
402B 15 rue Hélène Brion
75205 Paris cedex 13
Director : Giuseppe Baldacci
phone : +33 1 57 27 80 67
Subjects / Tools-Methodologies:
1 : evolution / natural variation, evolutionary genetics
2 : ecology / sampling, life history
3 : pathogens, immunity/ C. elegans, microscopy, genetics, RNAi,
Summary of lab's interests
Our team combines evolutionary, ecological and quantitative approaches to laboratory biology of a major model organism. The nematode worm C. elegans has become one of the major lab model organisms, yet little is known of its biology in the wild. Of particular interest is its mode of reproduction with selfing hermaphrodites and facultative males. To understand the biology of Caenorhabditis nematodes outside the laboratory, especially their outcrossing rate, population structure and ecology, we collect and study natural populations of C. elegans and other Caenorhabditis species (many of them new). After first isolating C. elegans from compost heaps, we recently found that C. elegans mostly proliferates in rotting fruits. We now aim to study the ecology and the structure of diversity of these natural populations. To study a model developmental system in its evolutionary context, we chose to focus on vulva formation, one of the best-studied developmental process in C. elegans. Vulva cell fate specification is an example of a biological system that is robust to stochastic noise and environmental change(for all precursor cell fates except one). Most biological processes are studied in the laboratory under one standard condition in one reference genetic background. In contrast, we aim to study the impact of environmental and genetic variation on vulva development. We explore the impact of the environment on the system (both on its output and on the signaling pathway activities leading to cell fate specification) and its evolvability upon random mutation. The observed buffering of the system\'s output to environmental variation results in buffering of some genetic variation, thus allowing for evolution in the process without change in its output. We reveal and study such cryptic evolution within C. elegans and among different Caenorhabditis species using various experimental approaches.
Summary of project
Coevolution of Caenorhabditis nematodes and natural pathogens Natural pathogens exert strong selective pressures on their host; host defence in turn provides a changing environment for the pathogen. Although laboratory studies on immunity of the nematode C. elegans mostly use human pathogens, natural pathogens are most relevant to study co-evolution between host and pathogen Sampling of natural populations of C. elegans by the Felix lab led to the isolation of many natural strains that are infected by pathogens, so far uncharacterized (except for a microsporidium, recently published in a collaborative work). The present project consists in: 1) Characterization of natural pathogens of the model organism C. elegans, focusing mostly on a common infection that causes degeneration of the cytoplasm and nucleus of intestinal cells (only the plasma membrane remains). Preliminary results suggest that this infection is caused by a virus (J. Piffaretti and M.-A. Félix, unpublished). 2) Characterization of genetic variation among natural Caenorhabditis isolates in sensitivity to these pathogens. 3) Characterization of the worm defence against the pathogen and of putative defences of the pathogen against worm immunity, using laboratory tools (mutants, RNAi). If the pathogen is a RNA virus, it will be very interesting to test the role of the RNAi machinery in anti-viral defence. 4) Co-evolution of host and pathogen. Such a system combining an animal and a virus is very favorable for experiments on co-evolution of host and pathogen, using either natural variation in host and pathogen or experimental evolution in the lab.