A newborn F-box gene blocks gene flow by selectively degrading phosphoglucomutase in species hybrids.

The establishment of reproductive barriers such as postzygotic ybrid ncompatibility (HI) remains the key to speciation. Gene duplication followed by differential functionalization has long been proposed as a major model underlying HI, but little supporting evidence exists. Here, we demonstrate that a newborn F-box gene, , of the nematode specifically inactivates an essential phosphoglucomutase encoded by in its sister species and their hybrids.

Transposon-mediated genic rearrangements underlie variation in small RNA pathways.

Transposable elements (TEs) can alter host gene structure and expression, whereas host organisms develop mechanisms to repress TE activities. In the nematode , a small interfering RNA pathway dependent on the helicase ERI-6/7 primarily silences retrotransposons and recent genes of likely viral origin. By studying gene expression variation among wild strains, we found that structural variants and transposon remnants likely underlie expression variation in and the pathway targets.

defective-pharynx and constipated mutants are resistant to Orsay virus infection.

animals with a compromised pharynx accumulate bacteria in their intestinal lumen and activate a transcriptional response that includes anti-bacterial response genes. In this study, we demonstrate that animals with defective pharynxes are resistant to Orsay virus (OrV) infection. This resistance is observed for animals grown on OP50 and on BIGb0172, a bacterium naturally associated with .

Caenorhabditis elegans immune responses to microsporidia and viruses.

The model organism Caenorhabditis elegans is susceptible to infection by obligate intracellular pathogens, specifically microsporidia and viruses. These intracellular pathogens infect intestinal cells, or, for some microsporidia, epidermal cells. Strikingly, intestinal cell infections by viruses or microsporidia trigger a common transcriptional response, activated in part by the ZIP-1 transcription factor.

Naturally-associated bacteria modulate Orsay virus infection of Caenorhabditis elegans.

Microbes associated with an organism can significantly modulate its susceptibility to viral infections, but our understanding of the influence of individual microbes remains limited. The nematode Caenorhabditis elegans is a model organism that in nature inhabits environments rich in bacteria. Here, we examine the impact of 71 naturally associated bacteria on C.

A QTL on chromosome IV explains a natural variation of QR.pap final position in .

In , the QR neuroblast and its progeny migrate from the posterior to the anterior part of the animal during the L1 stage. We previously showed that the final position of QR.pa daughters varies among wild isolates, with CB4932 displaying a particularly anterior QR.

Precise temporal control of neuroblast migration through combined regulation and feedback of a Wnt receptor.

Many developmental processes depend on precise temporal control of gene expression. We have previously established a theoretical framework for regulatory strategies that can govern such high temporal precision, but experimental validation of these predictions was still lacking. Here, we use the time-dependent expression of a Wnt receptor that controls neuroblast migration in as a tractable system to study a robust, cell-intrinsic timing mechanism in vivo.

Bacterial filamentation as a mechanism for cell-to-cell spread within an animal host.

Intracellular pathogens are challenged with limited space and resources while replicating in a single host cell. Mechanisms for direct invasion of neighboring host cells have been discovered in cell culture, but we lack an understanding of how bacteria directly spread between host cells in vivo. Here, we describe the discovery of intracellular bacteria that use filamentation for spreading between the intestinal epithelial cells of a natural host, the rhabditid nematode Oscheius tipulae.

Infection of by Species Reveals Shared Features in the Host Response to Oomycete Detection.

Oomycetes are a group of eukaryotic organisms that includes many important pathogens of animals and plants. Within this group, the genus is characterised by the presence of specialised gun cells carrying a harpoon-like infection apparatus. While several pathogens have been morphologically described, there are currently no host systems developed to study the infection process or host responses in the lab.

Selective Cleaning of Wild Caenorhabditis Nematodes to Enrich for Intestinal Microbiome Bacteria.

Caenorhabditis elegans (C. elegans) has proven to be an excellent model for studying host-microbe interactions and the microbiome, especially in the context of the intestines. Recently, ecological sampling of wild Caenorhabditis nematodes has discovered a diverse array of associated microbes, including bacteria, viruses, fungi, and microsporidia.

Balancing selection maintains hyper-divergent haplotypes in Caenorhabditis elegans.

Across diverse taxa, selfing species have evolved independently from outcrossing species thousands of times. The transition from outcrossing to selfing decreases the effective population size, effective recombination rate and heterozygosity within a species. These changes lead to a reduction in genetic diversity, and therefore adaptive potential, by intensifying the effects of random genetic drift and linked selection.

Temporally regulated cell migration is sensitive to variation in body size.

Few studies have measured the robustness to perturbations of the final position of a long-range migrating cell. In the nematode , the QR neuroblast migrates anteriorly, while undergoing three division rounds. We study the final position of two of its great-granddaughters, the end of migration of which was previously shown to depend on a timing mechanism.

A broad mutational target explains a fast rate of phenotypic evolution.

The rapid evolution of a trait in a clade of organisms can be explained by the sustained action of natural selection or by a high mutational variance, that is the propensity to change under spontaneous mutation. The causes for a high mutational variance are still elusive. In some cases, fast evolution depends on the high mutation rate of one or few loci with short tandem repeats.

Vertical transmission in nematodes of RNA molecules encoding a viral RNA-dependent RNA polymerase.

Here, we report on the discovery in nematodes of multiple vertically transmitted RNAs coding for putative RNA-dependent RNA polymerases. Their sequences share similarity to distinct RNA viruses, including bunyaviruses, narnaviruses, and sobemoviruses. The sequences are present exclusively as RNA and are not found in DNA form.

Selection and gene flow shape niche-associated variation in pheromone response.

From quorum sensing in bacteria to pheromone signalling in social insects, chemical communication mediates interactions among individuals in local populations. In Caenorhabditis elegans, ascaroside pheromones can dictate local population density; high levels of pheromones inhibit the reproductive maturation of individuals. Little is known about how natural genetic diversity affects the pheromone responses of individuals from diverse habitats.

Noda-Like RNA Viruses Infecting Nematodes: Sympatry, Diversity, and Reassortment.

Three RNA viruses related to nodaviruses were previously described to naturally infect the nematode and its relative, Here, we report on a collection of more than 50 viral variants from wild-caught We describe the discovery of a new related virus, the Mělník virus, infecting , which similarly infects intestinal cells. In France, a frequent pattern of coinfection of by the Santeuil virus and Le Blanc virus was observed at the level of an individual nematode and even a single cell. We do not find evidence of reassortment between the RNA1 and RNA2 molecules of Santeuil and Le Blanc viruses.