Marie Anne Felix

..Our results demonstrate the existence of intercellular cell-survival signals in nematodes and uncover an evolutionary variation in the role of the gonad in nematode vulval development...

..We finally discuss ways in which selection pressures on phenotypes can be inferred from a comparison of the phenotypic spectrum found on mutation with that found in the wild...

..The recently published genome of the nematode Caenorhabditis briggsae provides a drastic improvement in structural annotation of the C. elegans genome, as well as a promising source of evolutionary comparisons...

..the number, timing, and source of inductive signals from the gonad to the vulval precursor cells differ between the two morphs. These results show that discrete vulva developmental routes can be adopted by animals of the same genotype...

..Strikingly,a recent study finds that Wnts act to repress vulval differentiation in the nematode Pristionchus pacificus,1 demonstrating evolutionary flexibility in the use of intercellular signaling pathways...

..Part of the reason is that highly robust systems can accumulate cryptic variation that can serve as a source of new adaptations and evolutionary innovations. We point to some key challenges in improving our understanding of robustness...

..It is unknown how the roles and quantitative contributions of these signaling pathways have evolved in closely related Caenorhabditis species...

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..In particular, its unusual mode of reproduction with self-fertile hermaphrodites and facultative males raises the question of its frequency of outcrossing in natural populations...

..Second, we discuss the development of the C. elegans vulva. This example illustrates how development responds to variation in the environment while generating an invariant final phenotype...

..p competence without affecting their LIN-39 level. The centered vulval competence profile is thus under the control of the posterior Wnts and of cross-regulation of three HOM-C genes and prepatterns the later induction of vulval fates...

..Fourth, we discuss the evolutionary significance of environmental sensitivity of this developmental system...

..elegans and C. briggsae, however, produce self-fertile hermaphrodites instead of females. These transitions to hermaphroditism evolved convergently through distinct modifications of germline sex determination mechanisms...

..This study provides an empirical assessment of developmental bias and the evolution of mutationally accessible phenotypes and supports the notion that such bias may influence the directions of evolutionary change...

..Very little is known, however, about its ecology, including where it proliferates. In the past, C. elegans was mainly isolated from human-made compost heaps, where it was overwhelmingly found in the non-feeding dauer diapause stage...

..In addition, cultivation in the laboratory has led to adaptive evolution of the reference strain N2 to the laboratory environment, which may modify other phenotypes of interest...

..briggsae. We propose that evolutionary variation in the concentration or interpretation of the long-range Wnt gradient may be involved in the rapid evolution of P3.p fate in Caenorhabditis...

..C. elegans seems to follow metapopulation dynamics, and the maintenance of linkage disequilibrium despite a low yet significant level of outcrossing suggests that selection may act against the progeny of outcrossings...

..This discovery establishes a bona fide viral infection system to explore the natural ecology of nematodes, host-pathogen co-evolution, the evolution of small RNA responses, and innate antiviral mechanisms...

..p competence. Group 4 mutants display an abnormal centering of the vulval pattern on P7.p and suggest that a specific mechanism centers the vulval pattern on a single Pn.p cell...

..elegans sid-2 gene. Here we aimed to elucidate the evolution of the susceptibility to external RNAi in the Caenorhabditis genus...

..Like every biological system, this network displays genetic and -environmental epistasis...

..Due to its widespread occurrence and relatively high genetic diversity, O. tipulae may be a promising study species for evolutionary studies...

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..In addition, our results suggest that the vulva genetic screens would have yielded a different mutation spectrum, especially for Wnt pathway mutations, had they been performed in another C. elegans genetic background...

..CONCLUSIONS: Polymorphisms in vulval cell lineage are found within a given nematode species, and could be instrumental in explaining evolutionary variations between closely related species...

..Thus, whereas the final cell fate pattern of P11/12 is invariant, the developmental route leading to it is subject both to developmental indeterminacy and to evolutionary variations...

..CEW1 appear to be redundantly controlled by a gonad-independent mechanism and by a gonadal signal that operates partially independently of vulval fate induction...

..These studies have revealed that evolutionary variations between sister species affect those characters that show phenotypic developmental variants, that are mutable and that are polymorphic within species...

..elegans developmental biology and molecular genetics, biologists lack basic data for understanding the abundance and distribution of Caenorhabditis species in natural areas that are unperturbed by human influence...

..We present examples of cell biological processes, such as centrosome separation in prophase, spindle formation or cleavage furrow positioning, that support the first proposition. We propose experimental tests of these hypotheses...