Dana L. Miller et al. (2007) International Worm Meeting "Adaptation to hydrogen sulfide increases thermotolerance and lifespan."

Mark B. Roth, Dana L. Miller

[International Worm Meeting, 2007]

Hydrogen sulfide (H₂S), which is naturally produced in animal cells, has been shown to effect physiological changes that improve the capacity of mammals to survive environmental changes. We have investigated the physiological response of C. elegans to H₂S to begin to elucidate the molecular mechanisms of H₂S action. We show that nematodes exposed to H₂S are apparently healthy and do not exhibit phenotypes consistent with metabolic inhibition. However, we observed that animals exposed to H₂S had increased thermotolerance and lifespan and survived subsequent exposure to otherwise lethal concentrations of H₂S. Increased thermotolerance and lifespan is not observed in the sir-2.1(ok434) deletion mutant exposed to H₂S. However, mutants in the insulin signaling pathway (both daf-2 and daf-16), animals with mitochondrial dysfunction (isp-1 and clk-1) and a genetic model of caloric restriction (eat-2) all exhibit H₂S-induced increased thermotolerance. These data suggest that H₂S activates a pathway including SIR-2.1 that is separate from dietary restriction and insulin signaling that results in increased lifespan. Moreover, these studies suggest that SIR-2.1 activity may translate environmental change into physiological alterations that improve survival. It is interesting to consider the possibility that the mechanisms by which H₂S increases thermotolerance and lifespan in nematodes are conserved, and that studies using C. elegans may help explain beneficial effects observed in mammals exposed to H₂S.

Abergel, Z. et al. (2017) International Worm Meeting "Adaptation of the nematode C. elegans to hypoxia and reoxygenation stress reveals an unexpected function of the neuroglobin GLB-5 in innate immunity."

Zuckerman, B., Zelmanovich, V., Abergel, Z., Abergel, R., Gross, E., Smith, Y., Romero, L., Livshits, L.

[International Worm Meeting, 2017]

Deprivation of oxygen (hypoxia) followed by reoxygenation (H/R stress) is a major component in several pathological conditions such as vascular inflammation, myocardial ischemia, and stroke. However how animals adapt and recover from H/R stress remains an open question. Previous studies showed that the neuroglobin GLB-5(Haw) is essential for the fast recovery of the nematode Caenorhabditis elegans (C. elegans) from H/R stress. Here, we characterize the changes in neuronal gene expression during the adaptation of worms to hypoxia and recovery from H/R stress. Our analysis shows that innate immunity genes are differentially expressed during both adaptation to hypoxia and recovery from reoxygenation stress. Moreover, we reveal that the prolyl hydroxylase EGL-9, a known regulator of both adaptation to hypoxia and the innate immune response, inhibits the fast recovery from H/R stress through its activity in the O2-sensing neurons AQR, PQR, and URX. Finally, we show that GLB-5(Haw) acts in AQR, PQR, and URX to increase the tolerance of worms to bacterial pathogenesis. Together, our studies suggest that innate immunity and recovery from H/R stress are regulated by overlapping signaling pathways.

Walter L et al. (2010) Aging, Metabolism, Stress, Pathogenesis, and Small RNAs, Madison, WI "Role of the Homeodomain Protein CEH-23 in Longevity of Mitochondrial ETC Mutants in Caenorhabditis elegans"

Walter L, Lee S, Pace H, Chang H

[Aging, Metabolism, Stress, Pathogenesis, and Small RNAs, Madison, WI, 2010]

Mitochondrial dysfunctions have long been associated with aging and aging related diseases. Accumulating evidence in various model organisms, including yeast, worms, flies, and mice, indicates that mutants with a moderate reduction of mitochondrial electron transport chain (ETC) function exhibit lifespan extension. The mechanism of this conserved observation is poorly understood. Through an RNAi suppressor screen, we recently identified the homeodomain protein CEH-23 to play an important role in the longevity of long-lived mitochondrial ETC mutants. Inactivating ceh-23 can partially suppress the lifespan extension phenotype of several mitochondrial ETC mutants. This suppression is specific to mitochondrial ETC defective mutants, as long-lived mutants in other longevity pathways do not exhibit similar lifespan shortening upon ceh-23 inactivation. Interestingly, loss of ceh-23 did not suppress the slow development and reduced reproduction phenotypes associated with the long-lived mitochondrial ETC mutants, indicating that CEH-23 plays a specific role in longevity modulation. Furthermore, over-expression of ceh-23 in wild-type background causes longevity extension. All together, our findings suggest an important role of ceh-23 in promoting longevity in response to moderate mitochondrial defects in C. elegans. CEH-23 is a putative transcription factor in C. elegans and has been implicated in the transcriptional cascade regulating thermosensory neuron differentiation. However, its role in longevity was previously unknown. Further study will provide new insights into ceh-23 function, and will shed light on the molecular mechanism whereby altered mitochondrial ETC function modulates longevity.

Lee, C. et al. (2019) International Worm Meeting "Oyster mushrooms paralyze the nematode prey by triggering rapid cell necrosis via the sensory cilia."

Hsueh, Y., Lee, C., Yang, C., Chang, H.

[International Worm Meeting, 2019]

Multiple trophic interactions between fungi and nematodes exist in nature as they cohabitate in many ecosystems. Several fungal lineages have independently evolved to prey on nematodes to supplement nitrogen intake under nutrient-limiting conditions. One example is the common edible oyster mushroom Pleurotus ostreatus, which is known to be carnivorous to nematodes. The mycelium of the mushroom paralyzes the nematodes within a few minutes of contact. However, how exactly the mushroom paralyzes the nematodes is unknown. Here, we show that the nematicidal toxin produced by Pleurotus entered Caenorhabditis elegans from the cilia of sensory neurons, causing excessive influx of calcium and hyper-contraction in the head and pharyngeal muscle cells, and rapid necrosis of the entire nervous system. Genetic screens discovered that mutants became resistant to mushroom-induced paralysis all had loss of function mutations in genes required for ciliogenesis. Cell-specific rescue experiments demonstrate that multiple sensory neurons are involved in mushroom-triggered paralysis response and that intact cilia structure in a single sensory neuron is sufficient to be paralyzed by P. ostreatus. Massive cell necrosis of the entire nervous system occurred following the excessive influx of calcium in the muscle cells, and mutation in unc-68, a ryanodine receptor that functions as an intracellular calcium channel, suppressed cell necrosis. Lastly, we showed that in Pristionchus pacificus, a nematode species that was estimated to diverge from C. elegans 280-430 million years ago, sensory cilia are also required mushroom-triggered paralysis. In summary, our findings illustrate that the oyster mushrooms exploit an evolutionarily conserved mechanism to paralyze the nematode prey. We discovered the route of entry for the nematicidal toxin through the sensory cilia, caused sharp increase in the intracellular calcium level in the pharyngeal muscles, and triggered systemic cell necrosis in the nervous system. These findings identified a novel nematode-killing mechanism that is distinct from the widely used anthelmintic drugs such as ivermectin, levamisole, and aldicarb.

Rasika Kalamegham et al. (2004) East Coast Worm Meeting "EGL-26 belongs to the NlpC/P60 superfamily of putative enzymes and is closely related to a mammalian acyl transferase"

Wendy Hanna-Rose, Rasika Kalamegham

[East Coast Worm Meeting, 2004]

egl-26 was identified in a genetic screen to uncover mutants with vulval morphology defects. In egl-26 mutants the morphology of a single vulval toroid (vulF) is abnormal and a proper connection to the uterus is not made leading to the egg-laying defect. EGL-26 is a member of the NlpC/P60 superfamily of enzymes, which is characterized by a Histidine containing domain and a Cysteine containing domain (H-box and NC domain, respectively). EGL-26 along with other eukaryotic proteins belongs to a distinct subclass of NlpC/P60-related putative enzymes. The mammalian proteins lecithin: retinol acyltransferase or LRAT and H-ras revertant 107 or H-Rev107 are the most closely related to EGL-26. Both LRAT and H-Rev107 contain putative transmembrane domains in addition to the H-box and NC domains. Although EGL-26 contains no putative transmembrane domains, it is localized at the apical membrane of cells where it is expressed. Proper localization of LRAT within the retinal pigment epithelium is essential for its function. Significantly, an S-F substitution at amino acid 275 of EGL-26 found in the egl-26 (n481) allele causes mislocalization of an EGL-26::GFP fusion leading to general cytoplasmic expression as opposed to normal apical membrane localization. The corresponding Serine residue is conserved in both LRAT and H-Rev107. We are attempting to analyze the relationship between the mammalian proteins and EGL-26 by attempting a rescue of egl-26 mutants by expression of either LRAT or H-Rev107 or both. We plan to test the importance of membrane localization by restoring membrane localization to EGL-26n481 via addition of alternative membrane localization signals.

Jonathan H Freedman et al. (2005) International Worm Meeting "Changes in Gene Expression Associated with Exposure to Environmental Toxicants"

Michelle Chen, Yuxia Cui, Jonathan H Freedman, Sean Coughlan, Windy A Boyd

[International Worm Meeting, 2005]

When organisms are exposed to toxicants, they defend themselves against intracellular damage by activating the transcription of genes that encode proteins that defend the host, repair the damage, or remove/metabolize the toxicant. Changes in expression of these proteins following toxicant exposure is referred to as the stress-response. Since many of these stress-response proteins and the signal transduction cascades that regulate the stress-response are evolutionarily conserved, we hypothesize that exposure to environmental toxicants modulates the transcription of an evolutionarily conserved set of genes from yeast to mammals. To investigate this hypothesis we are comparing the expression profiles from yeast and C. elegans that were exposed to archetypical toxicants. In the present study we examined the responses of wild type C. elegans to the carcinogenic transition metal cadmium and the DNA alkylating agent N-methyl-N-nitro-nitrosoguanidine (MNNG). Toxicological studies for both cadmium and MNNG were performed to determined exposure times and toxicant concentrations. Bases on the effects of these agents on feeding, reproduction, and growth, nematodes were exposed to 0.1 mM cadmium and 4 ppm MNNG for 4h and 24h. Transcriptomes for cadmium- and MNNG-exposed nematodes were obtained by Agilents C. elegans oligonucleotide microarray analysis. This microarray contains ~20,000 targets, based on sequence information obtained from the WS105 release of WormPep, the C. elegans EST database and Genbank. Current analysis indicates that 47 genes are differential expressed after 4 h cadmium exposure, and 115 genes are differential expressed after a 24 h exposure (fold change&#8805;2, p<0/01). Over 400 genes were differentially expressed following MNNG exposure. Subsequently the functions of these genes will be identified and compared to identify conserved and divergent Gene Ontologys (GO), pathways (KEGG) and interactomes nodes (Cytoscape) among the gene whose levels of expression affected by cadmium and MNNG. The result will help us to discover not only expression profiles associated with specific toxicants, but also common stress-response genes regulated by different environmental toxicants. Moreover, this result will be incorporated into a larger study to compare the expression profiles from four species (yeast, C. elegans, zebrafish embryos and mice) exposed to different classes of toxicants in order to define evolutionarily conserved regulatory pathways that control the stress response.

Schwartz, Hillel et al. (2013) International Worm Meeting "Developing Heterorhabditis nematodes as an experimental system for the study of mutualistic symbiosis."

Schwartz, Hillel, Sternberg, Paul

[International Worm Meeting, 2013]

Entomopathogenic nematodes of the genus Heterorhabditis are insect killers that live in mutually beneficial symbiosis with pathogenic Photorhabdus bacteria. Photorhabdus is rapidly lethal to insects and to other nematodes, including C. elegans, but is required for Heterorhabditis growth in culture and for the insect-killing that defines the entomopathogenic lifestyle. The symbiosis between Heterorhabditis and Photorhabdus offers the potential to study the molecular genetic basis of their cooperative relationship. We developing tools to make such studies more feasible: we have been studying multiple nematodes of the genus Heterorhabditis and developing tools for the molecular genetic analysis of Heterorhabditis bacteriophora. Many species of Heterorhabditis and variants of Photorhabdus have been isolated; some pairings show specificity in their ability to establish a symbiotic relationship. To better understand these interactions and other variations in the lifestyles of Heterorhabditis, we have sequenced H. indica, H. megidis, H. sonorensis, and H. zealandica; a H. bacteriophora genome sequence is available. A comparison of these closely related species may help us to identify mechanisms that regulate the response to bacterial interactions and to find variations that correlate with differences in lifestyle or bacterial compatibility. In addition to genomics, we are developing H. bacteriophora as a laboratory organism. H. bacteriophora grows well on plates, has been reported to be susceptible to RNAi and transgenesis, and can develop as a selfing hermaphrodite, and so should be a powerful system for the molecular genetic study of the aspects of biology to which it is uniquely well suited, most prominently symbiosis. This potential is severely diminished by inconvenient sex determination: the self-progeny of hermaphrodites are mostly females with some males; at low density, their progeny are almost exclusively females. We have screened for and isolated a constitutively hermaphroditic mutant for use in molecular genetic studies of symbiosis. This mutant also offers the opportunity to explore the basis of hermaphrodite sex determination in H. bacteriophora.

Schwartz H et al. (2010) Aging, Metabolism, Stress, Pathogenesis, and Small RNAs, Madison, WI "Towards a SNP map for Heterorhabditis bacteriophora"

Sternberg P, Schwartz H

[Aging, Metabolism, Stress, Pathogenesis, and Small RNAs, Madison, WI, 2010]

Heterorhabditis bacteriophora is a species of insect-parasitic nematode that lives in mutually beneficial symbiosis with pathogenic Photorhabdus luminescens bacteria. P. luminescens bacteria are lethal to insects and to other nematodes, including the soil nematode Caenorhabditis elegans, but are required for H. bacteriophora growth. The symbiosis between H. bacteriophora and P. luminescens therefore offers the potential to study the molecular genetic basis of their cooperative relationship. We are interested in developing tools to make such studies more feasible; in particular, we propose to generate tools for genetic mapping in H. bacteriophora. We will test independent isolates of H. bacteriophora to ensure that the isolates are cross-fertile. We will then examine the abilities of these isolates to grow on and to become infected with different wild-type and mutant Photorhabdus bacteria. From these tests we will select an isolate on which we will use next-generation high-throughput sequencing technology for the purpose of refining the existing draft genome sequence and for the creation of a SNP map. We anticipate that this SNP map will enable us and the wider insect-parasitic nematode community to identify induced mutations and natural variations affecting the interactions between H. bacteriophora nematodes and pathogenic Photorhabdus bacteria.

Chu, Yu-De et al. (2013) International Worm Meeting "An RNAi-based screen for the DExD/H-box RNA helicases involved in Caenorhabditis elegans microRNA function."

Chan, Shih-Peng, Chen, Shin-Kai, Chu, Yu-De, Chen, Guan-Rong, Huang, Tao

[International Worm Meeting, 2013]

MicroRNAs (miRNAs) are small non-coding regulatory RNAs that regulate gene expression at the post-transcriptional level and are involved in a broad spectrum of biological processes. Rearrangements of inter- or intra-molecular RNA structures and conformational changes of ribonucleoprotein complexes in the multiple processes of the miRNA pathway have led to the involvement of RNA helicase activities but little is known so far. In eukaryotes, RNA helicases generally belong to the superfamily 2 (SF2) in helicase classification, especially the DExD/H-box helicase family. The DExD/H-box proteins have been shown in association with many cellular processes involving RNA. To better understand the possible roles of DExD/H-box RNA helicases in miRNA function, we employed RNAi screen to identify genetic interaction between C. elegans DExD/H-box RNA helicases and the let-7 miRNA, which controls the timing of cell cycle exit and terminal differentiation. In addition to the RNA helicase p72, a component of Drosha Microprocessor complex, and CGH-1 that has been reported to facilitate the function of miRNA-induced silencing complex (miRISC), we found several DExD/H-box RNA helicases, which are involved in ribosomal RNA processing, pre-mRNA splicing and mRNA surveillance, may also take part in miRNA biogenesis and/or function. (Support: National Science Council, Taiwan. NSC 100-2311-B-002-006-MY3).

Alexandre Neves et al. (2006) Development & Evolution Meeting "A Notch-GATA Transcription Code for Endoderm-Specific Gene Activation in C.elegans"

James Priess, Alexandre Neves

[Development & Evolution Meeting, 2006]

Several Notch interactions occur in rapid succession during early C.elegans embryogenesis, each resulting in a distinct fate. We have previously shown that ref-1, a gene distantly related to Drosophila E(spl), is a direct Notch target in all these interactions. We show here that ref-1 expression is controlled by multiple, Notch-dependent enhancers that are specific for each interaction. We have identified a 150bp enhancer that is specific to Notch interactions in the endoderm, and found similar enhancers with the same activity in C.briggsae and C.remanei. The endoderm enhancer contains multiple, conserved binding sites for LAG-1/Su(H) and GATA transcription factors. We demonstrate that all LAG-1/Su(H) and GATA sites are required for full activity of this enhancer. We provide evidence that a GATA transcription factor called ELT-2 is a cooperative factor for Notch in the endoderm. Ectopic expression of ELT-2 in non-endodermal lineages caused activation of the endoderm enhancer only in Notch-signaled cells, suggesting that the presence of the cooperative factor dictates in which Notch interaction a Notch-dependent enhancer becomes responsive in vivo. Previous studies in Drosophila showed that synergy between Su(H) and the bHLH transcription factor Daughterless requires a specific configuration of Su(H) sites, known as a Su(H) paired site, SPS. The endoderm enhancer contains a putative SPS. However, we find that Notch-GATA synergy does not require a SPS, and instead requires a non-SPS configuration of oriented LAG-1/Su(H) sites. Thus, it appears that that each configuration couples Notch signaling with a specific class of transcription factor.