Kroetz, Silvina et al. (2011) International Worm Meeting "Food Size and cGMP Affects Feeding Behavior in Pristionchus pacificus."

Kroetz, Silvina, Hong, Ray

[International Worm Meeting, 2011]

Hong Animals evolved different locomotory behaviors in order to find food in their environment. I studied the food seeking locomotion and pharyngeal pumping of nematodes Pristionchus pacificus on various food sources. For this study I used P. pacificus PS312, and the mutants Ppa-egl-4, which is a null mutation in the cGMP dependent protein kinase, and Ppa-obi-1, which is an oriental beetle pheromone insensitive mutant, and the double mutant Ppa-egl-4;obi-1. I tested these strains on plates containing no food and on E.coli OP50, HB101, Caulobacter crescentus (NA1000) and Bacillus subtilis. Locomotory behavior was analyzed using an automated tracking system, and pharyngeal pumping data was obtained by visually counting with a microscope at 80X magnification. I observed that locomotion of the strains differed on plates with no food and plates with food. On plates with no food, P. pacificus PS312 displayed a higher reversal rate compared to the Ppa-obi-1 strain. The double mutant egl-;obi-1 displayed similar locomotion patterns to Ppa-obi-1 on HB101. My results indicate that Ppa-obi-1 may act in either a parallel pathway, or upstream of Ppa-egl-4. Furthermore, when we compared PS312 pharyngeal pumping rates on and off food on two different size bacteria E. coli and C. crescentus, results showed a significant increased rate on PS312 on C. crescentus, which was the smaller bacteria. That is, PS312 raised on C. crescentus (NA1000) for 3 generations retained memory of the food experience regardless of whether they were removed from food or placed back on NA1000 as food. Increasing bacterial size using mutant C. crescentus strains seem to further decrease pumping rates off food. Our data suggest strong roles for food sizes and cGMP sensing proteins in maintaining feeding patterns in P. pacificus.

Kyle Ann Brooks et al. (2008) C.elegans Aging, Stress, Pathogenesis, and Heterochrony Meeting "Dietary Nutrients Affect Lifespan, Fat Storage, and Feeding Behavior in C. elegans"

Kyle Ann Brooks, Jennifer Watts, Bin Liang, Leon Avery, Young-jai You

[C.elegans Aging, Stress, Pathogenesis, and Heterochrony Meeting, 2008]

The optimum amounts of macronutrients in human diets is currently a subject of great interest. Diets emphasizing fat restriction, low carbohydrates or high protein content are promoted in popular books, but little is known about their long-term metabolic effects. We found that various E. coli strains commonly used to maintain C. elegans in most laboratory studies have distinct nutrient compositions. Nematodes maintained on these strains show significant differences in lifespan, fat storage, and feeding behavior. While all E. coli strains have a relatively high protein content, carbohydrate content varies in strains depending on whether or not they secrete a polysaccharide capsule. When growing on the capsule-secreting strain HB101, we found that wild type C. elegans show increased quiescence, reduced fat stores, and a shorter lifespan compared to C. elegans growing on the capsule-less strain OP50. Gene expression studies indicate an increase in fat metabolism in C. elegans growing on OP50, which may induce mitochondrial metabolism and a hormetic response that enables an extended lifespan. We find that the differences lifespan among worms grown on the two bacterial strains depends on efficient feeding, since eat-2 mutants show equally extended lifespans on both bacterial strains. We also find that AAK-2, a homolog of the large subunit of AMP-dependent kinase (AMPK), is necessary for the increased lifespan on OP50. Fat storage depends on feeding, since eat-2 shows indistinguishable low fat stores on both bacterial strains. Furthermore, mutants in the peptide transporter encoded by opt-2 store equally high amounts of fat when growing on both bacterial strains. Our studies indicate that various nutrient sensing pathways feed back to influence feeding behavior and metabolism, which in turn affect fat storage and lifespan.

Han, Michael et al. (2009) International Worm Meeting "Comparative Genomics using WormBase."

Han, Michael, Consortium, WormBase

[International Worm Meeting, 2009]

The recent increase in sequenced nematode genomes opened up possibilities to improve WormBase by integrating comparative genomics data. We included information on ortholog disease genes to enhance the role of C.elegans as model organism, and annotated the newly sequenced genomes with information derived from C.elegans. In addition, better integration into external databases (EnsEMBL Genomes, Inparanoid, TreeFam) and improvements on the WormBase website based on user feedback increase the accessibility of WormBase comparative data.

Tabuse Y (1997) International C. elegans Meeting "LITHIUM CAUSES DEVELOPMENTAL DISORDER IN C. ELEGANS"

Tabuse Y

[International C. elegans Meeting, 1997]

Lithium (Li) has long been known to have teratogenic effects on the development of many organisms, including sea urchin, Xenopus and Dictyostelium. In Li-treated Xenopus embryos, ventral blastmeres are respecified to develop into dorsal structures, leading to dorsalized embryos lacking ventral mesodermal tissues. In Dictyostelium, Li alters the fate of prespore cells to become prestalk cells instead. Besides teratogenic effects, Li is also known to be a most effective treatment of manic-depressive illness.!@Although several models have been proposed to explain Li action, the molecular mechanism has remained unclear. Recently, GSK (glycogen synthase kinase)-3b was proposed to be a target of Li, suggesting that Li affects the wnt signaling pathway. To understand the mechanism of Li action, I first examined the effect of Li on C. elegans embryogenesis. I inoculated N2 animals at the late L4 stage onto NG plates containing 20 mM LiCl, incubated them at 20 oC. The number of eggs produced by treated animals was reduced to about half of the untreated control. Although cell division seemed to proceed, no embryos hatched on Li plates. Treated-embryos developed to produce gut granules, but did not execute normal morphogenesis at later embryonic stages. To identify genes involved in the action of Li, I have begun to screen for Li-resistant mutants that propagated on Li-containing medium. Several mutants were isolated, and one of them was mapped on the left side of unc-42 on chromosome V. On Li plates, the hatching rate of mutant eggs cross-fertilized by wild-type males was essentially the same as that for self-fertilized mutant eggs. On the contrary, no wild-type eggs cross-fertilized by mutant males hatched on Li-containing plates. So, this mutation appeared to be maternal. Further genetic analyses of the mutants and the observation on the cellular phenotype of Li-treated embryos are underway.

Barnes TM et al. (1995) International C. elegans Meeting "UNC, INC."

Pak J, Barnes TM, Strapps W, Hekimi S

[International C. elegans Meeting, 1995]

We will present a progress report on the molecular and genetic characterization of a variety of unc genes. Come and visit our booth.

Birgitta Olofsson (2009) European Worm Neurobiology Meeting "Optimal foraging in C.elegans"

Birgitta Olofsson

[European Worm Neurobiology Meeting, 2009]

Variation in food quality and abundance requires animals to choose whether to stay on poor food patch or wander off in search of better food. Although optimal foraging choice is central to evolutionary survival, the molecular and neuronal mechanisms underlying it are poorly understood. I will present my work on this problem in C.elegans.

Peters, Lena et al. (2021) International Worm Meeting "C. elegans natural microbiota-mediated protection against pathogens"

Kissoyan, Kohar, Dierking, Katja, Drechsler, Moritz, Peters, Lena, Hamerich, Inga, Bode, Helge

[International Worm Meeting, 2021]

It has become increasingly clear how important gut bacteria are for the protection of the host against invading pathogens. The underlying mechanisms of microbiota-mediated protection, however, are largely unknown. In recent years C. elegans has been established as a model system to study host-microbiota interactions and microbiota-mediated protective effects against pathogens. Our work focuses on two Pseudomonas natural microbiota isolates, Pseudomonas lurida (MYb11) and Pseudomonas fluorescens (MYb115), which have previously been shown to protect C. elegans from infections with Bacillus thuringiensis (MYBt18247) and Pseudomonas aeruginosa (PA14). We are currently characterizing the influence of these microbiota isolates on the lifespan, reproduction, and most importantly, immune defense and aim to understand on how exactly microbiota-mediated protection is induced on both the microbiota and the host side. On the microbiota side, we have identified a biosynthetic gene cluster encoding a type I polyketide synthase (PKS), the resulting natural product induces the protective effect of MYb115 when worms are infected with Bt247. On the host side, we are currently using a reporter gene approach to identify genes and defense pathways involved in the worm response to infection. We will discuss our most recent results at the conference.

Palominos, Maria Fernanda et al. (2013) International Worm Meeting "Pathogen induced diapause formation requires the RNAi machinery."

Calixto, Andrea, Verdugo, Lidia, Chavez, Francisco, Palominos, Maria Fernanda

[International Worm Meeting, 2013]

The survival or demise of a host depends on its dynamic interaction with pathogens in its environment. We are investigating the effects of environmental and genetic variation on the survival and behavior of a host and its progeny, upon bacterial infection. We used C. elegans, as a host; and P. aeruginosa PAO1, an opportunistic human pathogen, as infectious agent. Environmental variation was performed supplementing or removing inorganic phosphate (Pi) from the growth media. Removal of Pi produces pigment expression and more virulent bacteria. Animals on P. aeruginosa PAO1 at high Pi survived better than at low Pi. Genetic variations were produced by mutations in both pathogen and host. We followed the viability of worms on P. aeruginosa PAO1 for two generations: Surprisingly, worms formed large amounts of dauers in the F2. We show that dauer formation is not specific of P. aeruginosa PAO1 exposure since they also formed dauers on Salmonella enterica. Dauer entry upon infection depends on transcriptional activation of DAF-16 but is independent from pheromone production since dauer formation was unaffected in daf-22 mutants. Worms preferred P. aeruginosa PAO1 over E. coli on high Pi. On low Pi initially preferred P. aeruginosa PAO1 but switch their preference for E. coli after the first hour. Systemic host responses, like RNA interference (RNAi) are likely to be most effective for defense against viruses since they spread far from their entry place. However the link between RNAi and bacterial pathogenesis is unknown. Several C. elegans RNAi mutants have a wild-type appearance under laboratory conditions when raised on non-pathogenic bacteria. While RNAi mutants are able to form dauers upon starvation, we found that both cell autonomous and environmental RNAi mutants, failed to form dauers on P. aeruginosa PAO1. Furthermore, RNAi mutants failed to avoid pathogenic bacteria in acute and chronic experiments. Our findings suggest that pathogen induced dauer formation is RNAi dependent and serves as trangenerational defense mechanism against bacterial infection.

Hinojosa Paiz, J. et al. (2019) International Worm Meeting "Illuminating gene regulatory roles of the sperm specific histone variant, HTAS-1."

Tabuchi, T., Chu, D.S., Rechtsteiner, A., Singh, S., Hinojosa Paiz, J.

[International Worm Meeting, 2019]

A main contributor to infertility is improper spermatogenesis. For proper progression of sperm development, correct gene regulatory patterns, which are governed by specific proteins, are vital. Histone variants are among these specialized proteins. Resembling fraternal twins, histone variants differ slightly in amino acid sequence from their core histone counterpart yet have alternative tissue specific effects on gene regulation. Our model organism, Caenorhabditis elegans, expresses four different histone H2A variants, one being the sperm specific HTAS-1 variant. Previous studies conducted on C. elegans have demonstrated that HTAS-1 is incorporated into chromatin late during male spermatogenesis and mutant htas-1 strains generate less progeny. Preliminary immunostaining data suggests HTAS-1 possesses a gene regulatory role as it colocalizes on autosomes and is absent on the silenced X chromosome. Yet, it is still unknown where HTAS-1 specifically localizes on genomic DNA and whether HTAS-1 directly regulates genes it binds in chromatin. To investigate where on DNA HTAS-1 is present, we conducted ChIP-seq on wild type mature sperm. We identified genomic sites of HTAS-1 chromatin integration, 26.5% of which are sperm specific genes. From this subset of sperm genes, we then asked whether these genes fall within genes that are potentially regulated by HTAS-1. To explore which genes are regulated by HTAS-1, I will perform RNA-seq on isolated mRNAs from mutant htas-1 and wild type male germlines. From RNA-seq data, I expect to find genes that are both up and down regulated when comparing mutant ?htas-1 ??and wild type transcript levels. Subsequently, to investigate if HTAS-1 regulates sperm specific genes it directly binds, I will perform smFISH on mutant htas-1 and wild type worms. From smFISH data, I expect to find the abundance of gene transcripts to increase or decrease with time proposing HTAS-1's role in the establishment of correct gene expression patterns, which also supports why it might not be found on the X chromosome. Findings from this study will help reveal potential gene targets for further investigation that are essential for proper male spermatogenesis. Knowledge on what genes HTAS-1 regulates and how it regulates these genes can give insight to how a histone variant is necessary for male fertility.

Susan Rai et al. (2005) International Worm Meeting "Genetic analysis for the effects of deprivation on behavioral response and body size"

Susan Rai, Catharine H Rankin

[International Worm Meeting, 2005]

The role of early experience on nervous system development has been studied in many organisms. However, with mammals the confound of maternal care has made it difficult to determine the effects of stimulation alone. C. elegans offspring receive no stimulation from the parent allowing us to explore the effects of complete isolation on development without the confounding variable of maternal nurturing. In this study, C. elegans were reared in either an isolated condition (without conspecifics to provide mechanosensory stimulation), or an enriched condition (colony) to test the effects of mechanosensory stimulation on nervous system development. The mechanical stimulus used to test the mechanosensory circuit was a mechanical tap delivered to the side of a Petri plated containing the worm. Worms raised in isolation were found to have a significantly smaller initial behavioural response (tap withdrawal response), and were significantly smaller in body size (worm length) than worms reared in a colony condition. The behaviour difference between isolate and colony raised worms is dependent on glr-1 (non-NMDA type glutamate receptor-1). However, body size of isolated worms is not glr-1 dependent suggesting the effects of isolation on body size are regulated by a different mechanism. A genetic analysis showed different genes altered the effects of isolation on response to tap and on worm length. The egl-4 pathway activated by a non-GLR-1 pathway from the touch cells, mediates the effects of worm length. These results dissociate the effects of isolation on mechanosensory responses and on development and suggest that these are two independent effects of developing in an environment with deprived sensory input. Brief mechanical stimulation (30 taps to plate) at all stages of development (L1-L4) reversed the effects of isolation on mechanosensory behaviour. This suggests that there is no critical period during which mechanosensory stimulation is necessary for the mechanosensory system to develop normally. To determine whether there was a critical period for the effects of isolation on body size, worms raised in isolation were transferred to a colony environment at various stages of larval development. Worms raised in isolation and transferred to colony at L3 remain significantly smaller in length compared to colony-raised worms, suggesting a critical period for worm length at L1/L2. These data indicate that the behavioral effects of isolation can be rescued at any time during development, while the effects of isolation on size can only be reversed early in development.