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[
ACS Chem Biol,
2012]
Entomopathogenic nematodes survive in the soil as stress-resistant infective juveniles that seek out and infect insect hosts. Upon sensing internal host cues, the infective juveniles regurgitate bacterial pathogens from their gut that ultimately kill the host. Inside the host, the nematode develops into a reproductive adult and multiplies until unknown cues trigger the accumulation of infective juveniles. Here, we show that the entomopathogenic nematode Heterorhabditis bacteriophora uses a small-molecule pheromone to control infective juvenile development. The pheromone is structurally related to the dauer pheromone ascarosides that the free-living nematode Caenorhabditis elegans uses to control its development. However, none of the C. elegans ascarosides are effective in H. bacteriophora, suggesting that there is a high degree of species specificity. Our report is the first to show that ascarosides are important regulators of development in a parasitic nematode species. An understanding of chemical signaling in parasitic nematodes may enable the development of chemical tools to control these species.
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Nature,
1998]
A genetic interference phenomenon in the nematode Caenorhabditis elegans has been described in which expression of an individual gene can be specifically reduced by microinjecting a corresponding fragment of double-stranded (ds) RNA. One striking feature of this process is a spreading effect: intereference in a broad region of the animal is observed following the injection of dsRNA into the extracellular body cavity. Here we show that C. elegans can respond in a gene-specific manner to dsRNA encountered in the environment. C. elegans normally feed on bacteria, ingesting and grinding them in the pharynx and subsequently absorbing bacterial contents in the gut. We find that Escherichia coli bacteria expressing dsRNA can confer specific interference effects on the nematode larvae that fed on them.
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[
FEMS Microbiol Lett,
2008]
The role of periplasmic disulfide oxidoreductase DsbA in Shiga toxin-producing Escherichia coli O157:H7 (STEC) was investigated. Deletion of dsbA (DeltadsbA) significantly decreased cell motility and alkaline phosphatase activity in STEC. STEC DeltadsbA also showed greater sensitivity to menadione and under low pH conditions. Significant reductions in surface attachment to both biotic (HT-29 epithelial cells) and abiotic (polystyrene and polyvinyl chloride) surfaces were observed in STEC DeltadsbA. In addition, no biofilm formation was detected in STEC DeltadsbA compared to wild-type cells in glass capillary tubes under continuous flow-culture system conditions. In the nematode model Caenorhabditis elegans-killing assay, the deletion of dsbA in STEC resulted in attenuated virulence compared to wild-type cells. STEC DeltadsbA was also found to have a reduced ability to colonize the nematode gut. These results suggest that DsbA plays important roles in biofilm formation and virulence in STEC cells.
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[
Curr Biol,
2000]
During signaling by the Notch receptor, Notch's intracellular domain is cleaved, moves to the nucleus and associates with a DNA-binding protein of the CSL class (CSL for CBF1, Suppressor of Hairless (Su(H)), LAG-1); as a result, target genes are transcriptionally activated (reviewed in [1,2]). In Caenorhabditis elegans, a glutamine-rich protein called LAG-3 forms a ternary complex with the Notch intracellular domain and LAG-1 and appears to serve as a transcriptional activator that is critical for signaling [3]. Although database searches failed to identify a LAG-3-related protein, we surmised that Notch signaling in other organisms might involve an analogous activity.
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[
Genesis,
2016]
Many developmental processes are inherently robust due to network organization of the participating factors and functional redundancy. The heterogeneity of the factors involved and their connectivity puts these processes at risk of abrupt system collapse under stress. The polarization of the one-cell C. elegans embryo constitutes such an inherently robust process with functional redundancy. However, how polarization is affected by acute stress has not been thoroughly investigated. Here, we report that heat shock (34C, 1 h) triggers a highly reproducible loss of the anterior and collapse of the posterior polarity domains. Temperature-dependent loss of cortical non-muscle myosin II drastically reduces cortical tension and leads to internalization of large plasma membrane domains including the membrane-associated polarity factor PAR-2. After internalization, plasma membrane vesicles and associated factors cluster around centrosomes and are thereby withdrawn from the polarization process. Transient formation of the posterior polarity domain suggests that microtubule-induced self-organization of this domain is not compromised after heat shock. Hence, our data uncover that the polarization system undergoes a temperature-dependent collapse under acute stress. This article is protected by copyright. All rights reserved.