Project description:This SuperSeries is composed of the following subset Series: GSE30977: C. elegans: Dauers and Dauer-Exit at 12 hour time-point vs. Mix-stage worms GSE31861: P. pacificus : Dauers and Dauer-Exit at 12 hour time-point vs. Mix-stage worms Refer to individual Series
Project description:Transcriptional profiling of P. pacificus worms from (1) dauer stage, or (2) dauer-exit at 12 hours stage, compared to mix-stage worms as a common reference. The goal was to determine genes regulated during dauer development and recovery or exit from dauer stage. This data was then compared to data generated for corresponding developmental stages in the C. elegans (see NCBI GEO series GSE30977) , to study evolution of developmental pathways regulating dauer development.
Project description:BackgroundAn organism can respond to changing environmental conditions by adjusting gene regulation and by forming alternative phenotypes. In nematodes, these mechanisms are coupled because many species will form dauer larvae, a stress-resistant and non-aging developmental stage, when exposed to unfavorable environmental conditions, and execute gene expression programs that have been selected for the survival of the animal in the wild. These dauer larvae represent an environmentally induced, homologous developmental stage across many nematode species, sharing conserved morphological and physiological properties. Hence it can be expected that some core components of the associated transcriptional program would be conserved across species, while others might diverge over the course of evolution. However, transcriptional and metabolic analysis of dauer development has been largely restricted to Caenorhabditis elegans. Here, we use a transcriptomic approach to compare the dauer stage in the evolutionary model system Pristionchus pacificus with the dauer stage in C. elegans.ResultsWe have employed Agilent microarrays, which represent 20,446 P. pacificus and 20,143 C. elegans genes to show an unexpected divergence in the expression profiles of these two nematodes in dauer and dauer exit samples. P. pacificus and C. elegans differ in the dynamics and function of genes that are differentially expressed. We find that only a small number of orthologous gene pairs show similar expression pattern in the dauers of the two species, while the non-orthologous fraction of genes is a major contributor to the active transcriptome in dauers. Interestingly, many of the genes acquired by horizontal gene transfer and orphan genes in P. pacificus, are differentially expressed suggesting that these genes are of evolutionary and functional importance.ConclusionOur data set provides a catalog for future functional investigations and indicates novel insight into evolutionary mechanisms. We discuss the limited conservation of core developmental and transcriptional programs as a common aspect of animal evolution.
Project description:Transcriptional profiling of P. pacificus worms from (1) dauer stage, or (2) dauer-exit at 12 hours stage, compared to mix-stage worms as a common reference. The goal was to determine genes regulated during dauer development and recovery or exit from dauer stage. This data was then compared to data generated for corresponding developmental stages in the C. elegans (see NCBI GEO series GSE30977) , to study evolution of developmental pathways regulating dauer development. Two-condition experiments. Experiment 1 = Dauers vs. Mix-stage worms. 4 biological replicates for each condition, including 2 dye-swaps. Experiment 2 = Dauer-Exit at 12 hour time-point s vs. Mix-stage worms. 3 biological replicates for each condition, including 1 dye-swaps. Total samples from both experiments 1 and 2 = 7.
Project description:Transcriptional profiling of C. elegans worms from (1) dauer stage, or (2) dauer-exit at 12 hours stage, compared to mix-stage worms as a common reference. The goal was to determine genes regulated during dauer development and recovery or exit from dauer stage. This data was then compared to data generated for corresponding developmental stages in the nematode Pristionchus pacificus (see NCBI GEO series GSE31861) , to study evolution of developmental pathways regulating dauer development.
Project description:Transcriptional profiling of C. elegans worms from (1) dauer stage, or (2) dauer-exit at 12 hours stage, compared to mix-stage worms as a common reference. The goal was to determine genes regulated during dauer development and recovery or exit from dauer stage. This data was then compared to data generated for corresponding developmental stages in the nematode Pristionchus pacificus (separate data-sets on a custom microarray platform designed by us and manufactured by Agilent) , to study evolution of developmental pathways regulating dauer development. Two-condition experiments. Experiment 1 = Dauers vs. Mix-stage worms. 4 biological replicates for each condition, including 2 dye-swaps. Experiment 2 = Dauer-Exit at 12 hour time-point s vs. Mix-stage worms. 4 biological replicates for each condition, including 2 dye-swaps. Total samples from both experiments 1 and 2 = 8.
Project description:The free-living soil nematode Caenorhabditis elegans adapts its development to the availability of food. When food is scarce and population density is high, worms enter a developmentally arrested non-feeding diapause stage specialized for long-term survival called the dauer larva. When food becomes available, they exit from the dauer stage, resume growth and reproduction. It has been postulated that compound(s) present in food, referred to as the "food signal", promote exit from the dauer stage. In this study, we have identified NAD+ as a component of bacterial extract that promotes dauer exit. NAD+, when dissolved in alkaline medium, causes opening of the mouth and ingestion of food. We also show that to initiate exit from the dauer stage in response to NAD+ worms require production of serotonin. Thus, C. elegans can use redox cofactors produced by dietary organisms to sense food.
Project description:To sense its population density and to trigger entry into the stress-resistant dauer larval stage, Caenorhabditis elegans uses the dauer pheromone, which consists of ascaroside derivatives with short, fatty acid-like side chains. Although the dauer pheromone has been studied for 25 years, its biosynthesis is completely uncharacterized. The daf-22 mutant is the only known mutant defective in dauer pheromone production. Here, we show that daf-22 encodes a homolog of human sterol carrier protein SCPx, which catalyzes the final step in peroxisomal fatty acid beta-oxidation. We also show that dhs-28, which encodes a homolog of the human d-bifunctional protein that acts just upstream of SCPx, is also required for pheromone production. Long-term daf-22 and dhs-28 cultures develop dauer-inducing activity by accumulating less active, long-chain fatty acid ascaroside derivatives. Thus, daf-22 and dhs-28 are required for the biosynthesis of the short-chain fatty acid-derived side chains of the dauer pheromone and link dauer pheromone production to metabolic state.
Project description:Parasitic hookworms and the free-living model nematode Caenorhabtidis elegans share a developmental arrested stage, called the dauer stage in C. elegans and the infective third-stage larva (L3) in hookworms. One of the key transcription factors that regulate entrance to and exit from developmental arrest is the forkhead transcription factor DAF-16/FoxO. During the dauer stage, DAF-16 is activated and localized in the nucleus. DAF-16 is negatively regulated by phosphorylation by the upstream kinase AKT, which causes DAF-16 to localize out of the nucleus and the worm to exit from dauer. DAF-16 is conserved in hookworms, and hypothesized to control recovery from L3 arrest during infection. Lacking reverse genetic techniques for use in hookworms, we used C. elegans complementation assays to investigate the function of Ancylostoma caninum DAF-16 during entrance and exit from L3 developmental arrest. We performed dauer switching assays and observed the restoration of the dauer phenotype when Ac-DAF-16 was expressed in temperature-sensitive dauer defective C. elegans daf-2(e1370);daf-16(mu86) mutants. AKT phosphorylation site mutants of Ac-DAF-16 were also able to restore the dauer phenotype, but surprisingly allowed dauer exit when temperatures were lowered. We used fluorescence microscopy to localize DAF-16 during dauer and exit from dauer in C. elegans DAF-16 mutant worms expressing Ac-DAF-16, and found that Ac-DAF-16 exited the nucleus during dauer exit. Surprisingly, Ac-DAF-16 with mutated AKT phosphorylation sites also exited the nucleus during dauer exit. Our results suggest that another mechanism may be involved in the regulation DAF-16 nuclear localization during recovery from developmental arrest.
Project description:Host-parasite research often focuses on a single host life stage, yet different life stages may exhibit different defenses. The nematode Caenorhabditis elegans has an alternate dispersal life stage, dauer. Despite dauer's importance in nature, we know little of how it responds to parasites. Previous research indicates that non-dauer C. elegans prefer to consume the virulent bacterial parasite, Serratia marcescens, when given a choice between the parasite and benign Escherichia coli. Here, we compared the preferences of dauer individuals from six strains of C. elegans to the preferences of other life stages. We found that dauer individuals exhibited reduced preference for S. marcescens, and dauers from some strains preferred E. coli to S. marcescens. In addition to testing food preference, a mechanism of parasite avoidance, we also measured host mortality rates after direct parasite exposure to determine if life stage also altered host survival. Overall, dauer individuals exhibited reduced mortality rates. However, dauer versus non-dauer larvae mortality rates also varied significantly by host strain. Collectively, we found evidence of dauer-induced parasite avoidance and reduced mortality in the presence of a parasite, but these effects were strain-specific. These results demonstrate the importance of host life stage and genotype when assessing infection dynamics.