Cilia and flagella are widespread eukaryotic subcellular components that are conserved from green algae to mammals. In different organisms they function in cell motility, movement of extracellular fluids and sensory reception. While the function and structural description of cilia and flagella are well established, there are many questions that remain unanswered. In particular, very little is known about the developmental mechanisms by which cilia are generated and shaped and how their components are assembled into functional machineries. To find genes involved in cilia development we used as a search tool a promoter motif, the X-box, which participates in the regulation of certain ciliary genes in the nematode Caenorhabditis elegans.By using a genome search approach for X-box promoter motif-containing genes (xbx genes) we identified a list of about 750 xbx genes (candidates). This list comprises some already known ciliary genes as well as new genes, many of which we hypothesize to be important for cilium structure and function. We derived a C. elegans X-box consensus sequence by in vivo expression analysis. We found that xbx gene expression patterns were dependent on particular Xbox nucleotide compositions and the distance from the respective gene start. We propose a model where DAF-19, the RFX-type transcription factor binding to the X-box, is responsible for the development of a ciliary module in C. elegans, which includes genes for cilium structure, transport machinery, receptors and other factors.
A complex between the ER resident protein FATP1 and the lipid droplet–localized DGAT2 protein facilitates lipid droplet expansion in C. elegans and mammalian cells.
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 -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 shortchain fatty acid-derived side chains of the dauer pheromone and link dauer pheromone production to metabolic state. ascaroside ͉ daf-22 ͉ dhs-28
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