GR Battu et al. (1999) International C. elegans Meeting "A genetic screen for inhibitors of the vulval induction pathway"

GR Battu, A Hajnal

[International C. elegans Meeting, 1999]

The vulva of the hermaphrodite is made from the descendants of three of the six equivalent Vulval Precursor Cells P3.p to P8.p (VPCs). In response to the inductive anchor cell signal, P6.p adopts the 1o fate which is to divide thrice to give 8 descendants that form the inner vulval tissue. A lateral signal from P6.p induces P5.p and P7.p to adopt the 2o fate which is to divide thrice to give 7 descendants each that form the outer vulval tissue. The remaining VPCs (P3.p, P4.p and P8.p) adopt the 3o fate which is to divide once and give 2 descendants that fuse with the hyp7 cell of the hypodermis. The anchor cell signal activates in P6.p a highly conserved RTKase/Ras/MAP kinase pathway that specifies the 1o fate. While many genes that are required for the transduction of the inductive signal have been isolated and characterized in detail, less is known about genes that negatively regulate vulval induction. Known inhibitors include sli-1, unc-101, sur-5, gap-1 and the class A and B Syn Muv genes. We have performed genetic screens to isolate and characterize novel inhibitors of vulval induction. Since animals containing a single mutation in an inhibitor usually do not exhibit excess vulval induction, we performed genetic screens in a sensitized gap-1(0) background for recessive mutations that exhibit a multivulva (Muv) phenotype. We thus isolated 9 new mutations (termed meg for m ultivulva e nhancer of g ap-1). Three of these mutations, meg-1(ga145), meg-2(ga139), meg-2(ga153), define two genes that map to chromosomal regions that do not contain known inhibitors of vulval development. Single mutants in meg-1 and meg-2 exhibit a wild type vulval phenotype. meg-1; gap-1 animals exhibit a 70% penetrant Muv phenotype but no other obvious defects. In addition to a 100% penetrant Muv phenotype, meg-2; gap-1 animals exhibit partial sterility, suggesting an involvement of meg-2 in oogenesis. Using a combination of three-factor crosses and deficiency mapping, we have located meg-1 on LGII between fer-15 and zyg-9 . To clone the gene, we are currently injecting YAC and cosmid clones that span this region into meg-1; gap-1 animals and are looking for rescue of the Muv phenotype. Similar studies with meg-2 are in the offing.

Ruan Q et al. (2015) J Ethnopharmacol "Beneficial effects of Glycyrrhizae radix extract in preventing oxidative damage and extending the lifespan of Caenorhabditis elegans."

Wang D, Duan J, Ruan Q, Wang M, Qiao Y, Zhao Y, Xu Y

[J Ethnopharmacol, 2015]

ETHNOPHARMACOLOGICAL RELEVANCE: Glycyrrhizae radix (GR) is a medicinal herb extensively used in traditional Chinese medicine. This study aimed to evaluate the pharmacological effect of GR and the possible mechanisms of GR, to provide a pharmacological basis in traditional medicine. MATERIALS AND METHODS: In the present study, C. elegans (L1-larvae to young adults) was exposed to 0.12-0.24g/mL of GR in 12-well sterile tissue culture plates at 20C in the presence of food. Lethality, growth, lifespan, reproduction, locomotion, metabolism, intestinal autofluorescence, and reactive oxygen species (ROS) production assays were performed to investigate the possible safety profile and beneficial effects of GR in these nematodes. We found that the lifespan of nematodes exposed to 0.18-0.24g/mL of GR was extended. We then determined the mechanism of the longevity effect of GR using quantitative reverse transcription PCR and oxidative stress resistance assays induced by heat and paraquat. RESULTS: Prolonged exposure to 0.12-0.24g/mL of GR did not induce lethality, alter body length, morphology or metabolism, affect brood size, locomotion, the development of D-type GABAergic motor neurons, or induce significant induction of intestinal autofluorescence and intestinal ROS production. In C. elegans, pretreatment with GR suppressed the damage due to heat-stress or oxidative stress induced by paraquat, a ROS generator, on lifespan, and inhibited the induction of intestinal ROS production induced by paraquat. Moreover, prolonged exposure to GR extended lifespan, increased locomotion and decreased intestinal ROS production in adult day-12 nematodes. Furthermore, prolonged exposure to GR significantly altered the expression patterns of genes encoding the insulin-like signaling pathway which had a key role in longevity control. Mutation of daf-16 gene encoding the FOXO transcription factor significantly decreased lifespan, suppressed locomotion, and increased intestinal ROS production in GR exposed adult nematodes. CONCLUSIONS: GR is relatively safe and has protective effects against the damage caused by both heat-stress and oxidative stress at the examined concentrations. Furthermore, GR is capable of extending the lifespan of nematodes, and the insulin-like signaling pathway may play a crucial role in regulating the lifespan-extending effects of GR.

Barry CS et al. (2006) Proc Natl Acad Sci U S A "Ripening in the tomato Green-ripe mutant is inhibited by ectopic expression of a protein that disrupts ethylene signaling."

Giovannoni JJ, Barry CS

[Proc Natl Acad Sci U S A, 2006]

To achieve full ripening, climacteric fruits, such as tomato require synthesis, perception and signal transduction of the plant hormone ethylene. The nonripening phenotype of the dominant Green-ripe (Gr) and Never-ripe 2 (Nr-2) mutants of tomato is the result of reduced ethylene responsiveness in fruit tissues. In addition, a subset of ethylene responses associated with floral senescence, abscission, and root elongation are also impacted in mutant plants, but to a lesser extent. Using positional cloning, we have identified an identical 334-bp deletion in a gene of unknown biochemical function at the Gr/Nr-2 locus. Consistent with a dominant gain of function mutation, this deletion causes ectopic expression of Gr/Nr-2, which in turn leads to ripening inhibition. A CaMV35::GR transgene recreates the Gr/Nr-2 mutant phenotype but does not lead to a global reduction in ethylene responsiveness, suggesting tissue-specific modulation of ethylene responses in tomato. Gr/Nr-2 encodes an evolutionary conserved protein of unknown biochemical function that we associate here with ethylene signaling. Because Gr/Nr-2 has no sequence homology with the previously described Nr (Never-ripe) ethylene receptor of tomato we now refer to this gene only as GR. Identification of GR expands the current repertoire of ethylene signaling components in plants and provides a tool for further elucidation of ethylene response mechanisms and for controlling ethylene signal specificity in crop plants.

Jeong JH et al. (2023) Nat Commun "A new AMPK isoform mediates glucose-restriction induced longevity non-cell autonomously by promoting membrane fluidity."

Jeong JH, Kim CA, Kwon KS, Lee KP, Shin MG, Jung Y, Lee SM, Kim N, Kim S, Hwang GS, Han JS, Kwon ES, Yang YR, Park M, Kang MS, Park SH

[Nat Commun, 2023]

Dietary restriction (DR) delays aging and the onset of age-associated diseases. However, it is yet to be determined whether and how restriction of specific nutrients promote longevity. Previous genome-wide screens isolated several Escherichia coli mutants that extended lifespan of Caenorhabditis elegans. Here, using ¹H-NMR metabolite analyses and inter-species genetics, we demonstrate that E. coli mutants depleted of intracellular glucose extend C. elegans lifespans, serving as bona fide glucose-restricted (GR) diets. Unlike general DR, GR diets don't reduce the fecundity of animals, while still improving stress resistance and ameliorating neuro-degenerative pathologies of Aβ₄₂. Interestingly, AAK-2a, a new AMPK isoform, is necessary and sufficient for GR-induced longevity. AAK-2a functions exclusively in neurons to modulate GR-mediated longevity via neuropeptide signaling. Last, we find that GR/AAK-2a prolongs longevity through PAQR-2/NHR-49/Δ9 desaturases by promoting membrane fluidity in peripheral tissues. Together, our studies identify the molecular mechanisms underlying prolonged longevity by glucose specific restriction in the context of whole animals.

Zhao Y et al. (2015) Nanomedicine "Glycyrrhizic acid, active component from Glycyrrhizae radix, prevents toxicity of graphene oxide by influencing functions of microRNAs in nematode Caenorhabditis elegans."

Jia R, Wang D, Zhao Y, Qiao Y

[Nanomedicine, 2015]

We investigated effects of pretreatment with Glycyrrhizae radix (GR) or its specific components on toxicity of graphene oxide (GO) in Caenorhabditis elegans. GR pretreatment prevented GO toxicity on function of both primary and secondary targeted organs. Among active components in GR, the beneficial effects of GR were attributable to the presence of glycyrrhizic acid. Glycyrrhizic acid pretreatment suppressed translocation of GO into secondary targeted organs through intestinal barrier. Moreover, glycyrrhizic acid pretreatment recovered expression patterns of dysregulated microRNAs (miRNAs) induced by GO, and genes required for oxidative stress control acted as targeted genes for some of these miRNAs. Among these miRNAs, mir-360 mutation enhanced beneficial effects of glycyrrhizic acid. We hypothesize that glycyrrhizic acid may prevent GO toxicity and translocation by influencing functions of miRNAs which upstream regulate functions of their targeted genes. Furthermore, glycyrrhizic acid had potential to extend lifespan, and to suppress accelerated aging process induced by GO. Glycyrrhizic acid prevented GO toxicity by influencing functions of miRNAs which upstream regulate functions of targeted genes and suppressing accelerated aging process induced by GO.

Rudich P et al. (2017) Hum Mol Genet "Nuclear localized C9orf72 associated arginine containing dipeptides exhibit age-dependent toxicity in C. elegans."

Lamitina T, Bhan Pandey U, Watkins SC, Monaghan J, Snoznik C, Rudich P

[Hum Mol Genet, 2017]

A hexanucleotide repeat expansion mutation in the C9orf72 gene represents a prevalent genetic cause of several neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Non-canonical translation of this repeat gives rise to several distinct dipeptide protein species that could play pathological roles in disease. Here, we show in the model system C. elegans that expression of the arginine-containing dipeptides, but not alanine-containing dipeptides, produces toxic phenotypes in multiple cellular contexts, including motor neurons. Expression of either (PR)50 or (GR)50 during development caused a highly penetrant developmental arrest, while post-developmental expression caused age-onset paralysis. Both (PR)50- and (GR)50-GFP tagged dipeptides were present in the nucleus and nuclear localization was necessary and sufficient for their toxicity. Using an inducible expression system, we discovered that age-onset phenotypes caused by (PR)50 required both continual (PR)50 expression and an aged cellular environment. The toxicity of (PR)50 was modified by genetic mutations that uncouple physiological ageing from chronological ageing. However, these same mutations failed to modify the toxicity of (GR)50, suggesting that (PR)50 and (GR)50 exert their toxicity through partially distinct mechanism(s). Changing the rate of physiological ageing also mitigates toxicity in other C. elegans models of ALS, suggesting that the (PR)50 dipeptide might engage similar toxicity mechanisms as other ALS disease-causing proteins.

Robertson HM (2015) Chem Senses "The Insect Chemoreceptor Superfamily Is Ancient in Animals."

Robertson HM

[Chem Senses, 2015]

The insect chemoreceptor superfamily consists of 2 gene families, the highly diverse gustatory receptors (GRs) found in all arthropods with sequenced genomes and the odorant receptors that evolved from a GR lineage and have been found only in insects to date. Here, I describe relatives of the insect chemoreceptor superfamily, specifically the basal GR family, in diverse other animals, showing that the superfamily dates back at least to early animal evolution. GR-Like (GRL) genes are present in the genomes of the placozoan Trichoplax adhaerens, an anemone Nematostella vectensis, a coral Acropora digitifera, a polychaete Capitella teleta, a leech Helobdella robusta, the nematode Caenorhabditis elegans (and many other nematodes), 3 molluscs (a limpet Lottia gigantea, an oyster Crassostrea gigas, and the sea hare Aplysia californica), the sea urchin Strongylocentrotus purpuratus, and the sea acorn Saccoglossus kowalevskii. While some of these animals contain multiple divergent GRL lineages, GRLs have been lost entirely from other animal lineages such as vertebrates. GRLs are absent from the ctenophore Mnemiopsis leidyi, the demosponge Amphimedon queenslandica, and 2 available chaonoflagellate genomes, so it remains unclear whether this superfamily originated before or during animal evolution.

Robertson HM et al. (2003) Proc Natl Acad Sci U S A "Molecular evolution of the insect chemoreceptor gene superfamily in Drosophila melanogaster."

Warr CG, Robertson HM, Carlson JR

[Proc Natl Acad Sci U S A, 2003]

The insect chemoreceptor superfamily in Drosophila melanogaster is predicted to consist of 62 odorant receptor (Or) and 68 gustatory receptor (Gr) proteins, encoded by families of 60 Or and 60 Gr genes through alternative splicing. We include two previously undescribed Or genes and two previously undescribed Gr genes; two previously predicted Or genes are shown to be alternative splice forms. Three polymorphic pseudogenes and one highly defective pseudogene are recognized. Phylogenetic analysis reveals deep branches connecting multiple highly divergent clades within the Gr family, and the Or family appears to be a single highly expanded lineage within the superfamily. The genes are spread throughout the Drosophila genome, with some relatively recently diverged genes still clustered in the genome. The Gr5a gene on the X chromosome, which encodes a receptor for the sugar trehalose, has transposed from one such tandem cluster of six genes at cytological location 64, as has Gr61a, and all eight of these receptors might bind sugars. Analysis of intron evolution suggests that the common ancestor consisted of a long N-terminal exon encoding transmembrane domains 1-5 followed by three exons encoding transmembrane domains 6-7. As many as 57 additional introns have been acquired idiosyncratically during the evolution of the superfamily, whereas the ancestral introns and some of the older idiosyncratic introns have been lost at least 48 times independently. Altogether, these patterns of molecular evolution suggest that this is an ancient superfamily of chemoreceptors, probably dating back at least to the origin of the arthropods.

Kaziales A et al. (2020) Sci Rep "Glucocorticoid receptor complexes form cooperatively with the Hsp90 co-chaperones Pp5 and FKBPs."

Marcus K, Barkovits K, Richter K, Kaziales A

[Sci Rep, 2020]

The function of steroid receptors in the cell depends on the chaperone machinery of Hsp90, as Hsp90 primes steroid receptors for hormone binding and transcriptional activation. Several conserved proteins are known to additionally participate in receptor chaperone assemblies, but the regulation of the process is not understood in detail. Also, it is unknown to what extent the contribution of these cofactors is conserved in other eukaryotes. We here examine the reconstituted C. elegans and human chaperone assemblies. We find that the nematode phosphatase PPH-5 and the prolyl isomerase FKB-6 facilitate the formation of glucocorticoid receptor (GR) complexes with Hsp90. Within these complexes, Hsp90 can perform its closing reaction more efficiently. By combining chemical crosslinking and mass spectrometry, we define contact sites within these assemblies. Compared to the nematode Hsp90 system, the human system shows less cooperative client interaction and a stricter requirement for the co-chaperone p23 to complete the closing reaction of GR-Hsp90-Pp5/Fkbp51/Fkbp52 complexes. In both systems, hormone binding to GR is accelerated by Hsp90 alone and in the presence of its cofactors. Our results show that cooperative complex formation and hormone binding patterns are, in many aspects, conserved between the nematode and human systems.

de Pomerai DI et al. (2002) Enzyme Microb Technol "Growth and maturation of the nematode Caenorhabditis elegans following exposure to weak microwave fields."

Allan J, Brunt G, Djerbib L, Dawe A, Daniells C, de Pomerai DI

[Enzyme Microb Technol, 2002]

Prolonged exposure to weak microwave fields (750-1000 MHz, 0.5 W) at 25degreesC induces a heat-shock response in transgenic C. elegans strains carrying hsp16 reporter genes [1]. A comparable response to heat alone requires a substantially higher temperature of 28degreesC, suggesting that microwave heating of worms or of the system as a whole might provide a sufficient explanation, although this can be ruled out by indirect arguments [1]. Here we investigate two further biological consequences of prolonged microwave exposure at 25degreesC in synchronised cultures of wild-type worm larvae, namely alterations in (i) growth rate (GR) and (ii) the proportion of worms later maturing into egg-bearing adults (MP). Both of these parameters are significantly increased following microwave exposure (GR by 8-11%, and MP by 28-40%), whereas both are significantly decreased (GR by 10% and MP almost abolished) after mild heat treatment at 28degreesC for the same period. It follows that the biological consequences of microwave exposure are opposite to, and therefore incompatible with, those attributable to mild heating. This evidence does not in itself necessitate a non-thermal mechanism, but does eliminate explanations that invoke the bulk heating of tissues by microwaves. This latter, however, remains the sole basis for current regulations governing microwave