Caenorhabditis Elegans Strains Research Articles

Effect of benzimidazole drugs on tubulin in benzimidazole resistant and susceptible strains of Caenorhabditis elegans

An in vitro assay was used to determine efficacy and if side resistance was present to benzimidazole anthelmintics tested against Caenorhabditis elegans after selection with albendazole. Side resistance was present to all the benzimidazoles tested, except for oxibendazole and parbendazole. At a concentration of 1 mM, all of the drugs, except thiabendazole, were effective in killing 100% of the albendazole susceptible worms. Tubulin from albendazole resistant and susceptible C. elegans was isolated and run on polyacrylamide gels. Western blots with anti-tubulin antibody showed that the albendazole resistant strain had an altered tubulin. Electron microscopy of albendazole-treated drug resistant worms showed microtubules throughout the intestinal cells. Microtubules were not observed in albendazole-treated drug susceptible worms.

Radiation sensitivity and DNA repair in Caenorhabditis elegans strains with different mean life spans

The sensitivities to three DNA damaging agents (UV and gamma-radiation, methyl methanesulfonate) were measured in four recombinant inbred (RI) strains of Caenorhabditis elegans with mean life spans ranging from 13 to 30.9 days, as well as in the wild-type strains used to derive these RI's. Sensitivities at several stages in the developmental cycle were tested. There were no significant correlations between mean life span and the lethal effects of these 3 agents. Excision of two UV-radiation-induced DNA photoproducts was also measured. Long-lived strains were no more repair competent than shorter-lived strains. These data indicate that DNA repair plays at best a minor role in the aging process of C. elegans.

Genetic mapping of the 5S rRNA gene cluster of the nematode Caenorhabditis elegans.

We have identified a restriction fragment length difference (RFLD) affecting the genomic sequences immediately flanking the 5S rRNA gene cluster in the Bristol and Bergerac strains of the nematode Caenorhabditis elegans. We have used this RFLD as a molecular marker to follow the segregation of the 5S rRNA gene cluster through a series of two- and three-factor interstrain crosses. Our results show that the 5S rRNA gene cluster maps between unc-76 and dpy-21 on the right arm of linkage group V. This genetic localization provides a linkage group V "landmark" with which to localize other cloned sequences by in situ hybridization.

Extrachromosomal copies of transposon Tc1 in the nematode Caenorhabditis elegans.

Extrachromosomal copies of the 1.6-kilobase transposable element Tc1 are present at the level of between 0.1 and 1.0 copy per cell in Caenorhabditis elegans strain Bergerac. Extrachromosomal elements were detected and studied using Southern hybridizations employing a Tc1-specific probe. The amount of extrachromosomal Tc1 DNA was roughly constant during development in Bergerac, which has approximately 300 integrated chromosomal copies of Tc1 in its haploid genome. Extrachromosomal Tc1 DNA was not detected in strain Bristol, which has 30 chromosomal copies of Tc1. Three forms of extrachromosomal DNA were detected. The predominant form was a 1.6-kilobase linear molecule with ends corresponding to the ends of an integrated Tc1 element. The other two forms were, respectively, relaxed and supercoiled circular copies of the element. Structural assignments were based on electrophoretic mobility, the results of sedimentation velocity and equilibrium density gradient experiments, and on the sizes of the products produced by treatment of purified extrachromosomal DNA with restriction endonucleases. The suggestion is made that these extrachromosomal transposable elements are the products of excision events known to be occurring at high frequency in somatic cells in Bergerac.

Triplo-X hermaphrodite of Caenorhabditis elegans: pachytene karyotype analysis, synaptonemal complexes, and pairing mechanisms

Pairing of the three X chromosomes in the triplo-X strain of Caenorhabditis elegans occurs at pachytene in a two-by-two fashion such that one bivalent and one univalent are formed. The XX bivalent pairs synchronously with the autosomes and the univalent X remains in a similar chromatic state as the rest of the chromosomal complement. Normal tripartite synaptonemal complexes (SC) are formed between all bivalents. The univalent X lacks a SC and an axial core is not observed. The condensation of the univalent X in the triplo-X is different than in the male where the univalent X is heterochromatic. This real difference in condensation states of the chromatin may explain the fact that the univalent X is maintained in the male line yet it is easily lost in the triplo-X strain.

Genetic analysis of life-span in Caenorhabditis elegans.

Crosses between Bristol and Bergerac strains of the self-fertilizing hermaphroditic nematode Caenorhabditis elegans do not show the heterosis effects for life-span that complicate analysis of interstrain crosses with Drosophila or mice. Instead they yield F1 progeny with life-spans similar to those of the parent strains. By analysis of life-span variation among progeny F2 populations from such crosses and by two independent analyses of life-spans among recombinant inbred lines derived from F2 individuals by 18 rounds of self-fertilization, we estimate that the heritability of life-span in C. elegans is between 20% and 50%. Recombinant inbred lines show a range in mean life-spans of 10 days to 31 days compared to life-spans of about 18 days for each of the two parental strains. We conclude that life-span variation in C. elegans has a substantial genetic component and that this organism offers promising opportunities for selective breeding of longer-lived strains and genetic analysis of senescence.

Molecular relationships between closely related strains and species of nematodes.

Electrophoretic comparisons have been made for 24 enzymes in the Bergerac and Bristol strains of Caenorhabditis elegans and the related species, Caenorhabditis briggsae. No variation was detected between the two strains of C. elegans. In contrast, the two species, C. elegans and C. briggsae exhibited electrophoretic differences in 22 of 24 enzymes. A consensus 5S rRNA sequence was determined for C. elegans and found to be identical to that from C. briggsae. By analogy with other species with relatively well established fossil records it can be inferred that the time of divergence between the two nematode species is probably in the tens of millions of years. The limited anatomical evolution during a time period in which proteins undergo extensive changes supports the hypothesis that anatomical evolution is not dependent on overall protein changes.

Analysis of the constancy of DNA sequences during development and evolution of the nematode Caenorhabditis elegans.

In order to test for the occurrence of rearrangements in DNA during development and to assess the rate of DNA divergence during evolution, we have compared restriction fragments derived from DNA from four sources: sperm cells and somatic tissues of one strain of the nematode Caenorhabditis elegans, somatic tissues of a second strain of the same species, and whole animals of a closely related species. Restriction fragments were detected by hybridizing radioactive cloned fragments to restriction digests that had been fractionated by size on agarose gels and transferred to nitrocellulose sheets. In this way, approximately 50 BamHI restriction fragments were visualized and compared. Fragments from sperm and somatic DNAs were found to be identical; 15% differed in size between the two strains. Little cross homology was found between the two species. We conclude that, if rearrangements occur in C. elegans DNA during development, they must affect fewer than a few percent of the restriction fragments or restriction sites. The difference found between the two strains and the two species is surprisingly great.

Osmotic avoidance defective mutants of the nematode Caenorhabditis elegans.

A wild-type strain of the nematode Caenorhabditis elegans has been shown to avoid high concentrations of a number of sugars and salts. Individual and population assays for this response were developed and mutants were selected for their inability to avoid high concentrations of fructose or NaCl, Seven nonavoiding mutants representing six complementation groups were isolated and characterized. Genetic studies indicate that the mutants each carry a single recessive mutation responsible for the defective osmotic avoidance behavior. The map locations of the six complementation groups identified by these mutations have been determined. Mutants isolated for their inability to avoid fructose are also unable to avoid NaCl and vice versa. The mutants move normally, exhibit normal touch sensitivity, and, like wild type, follow isotherms in a radial thermal gradient. All of the mutants are at least partially defective in the attraction to sodium chloride exhibited by wild type. None of the mutants is temperature sensitive, and all exhibit defective osmotic avoidance behavior as young L1 larvae. Preliminary anatomical studies indicate selective sensory neuron changes in at least one mutant.

The life cycle of the nematode Caenorhabditis elegans: II. A simplified method for mutant characterization

A simple method for characterizing the development and reproduction of mutant strains of the small nematode Caenorhabditis elegans has been developed. “3-egg” populations of nematodes, started with three synchronously laid eggs and allowed to develop undisturbed for about two generations, are measured on the electronic nematode counter, and the resulting size distributions are interpreted by a computer. The computer compares the observed distribution to an expected distribution, generated by assuming the developmental curves previously measured for the wild-type C. elegans; if the distributions do not agree, the computer independently varies scale factors for developmental rate, size, egg-laying rate, and spread until the expected distribution best approximates the observed one. The resulting factors quantify any mutant defect of growth or reproduction, and the poorness of fit tells how greatly the mutant's development differs from that of the wild-type in ways other than those allowed for by the four scale changes. The computer program is shown to be able to fit wild-type C. elegans 3-egg populations grown for various lengths of time at 20°C. Three-egg populations of wild-type animals grown at 16 and 25°C are fitted by the computer and give altered developmental parameters consistent with those previously measured by more direct means. Nine behavioral and morphological mutants have been analyzed by this method. All show some developmental alterations from the wild-type. Fertility seems to be more adversely affected than growth. One mutant has been studied in more detail to determine the specific ways in which it differs from the wild-type.

Genetic Control of Differential Heat Tolerance in Two Strains of the Nematode Caenorhabditis elegans

Two strains (Bergerac and Bristol) of the nematode Caenorhabditis elegans, with different temperature tolerances, were reared axenically at 23 degrees to 25 degrees C. The Bergerac strain is heat sensitive (that is, it is sterile at maturity), whereas the Bristol strain is heat resistant (that is, it matures and reproduces normally). Hybrid hermaphrodites (F(1)), produced by crossing Bristol males and Bergerac hermaphrodites, are heat tolerant. Heat sensitivity segregates as a simple Mendelian recessive in the F(2) and F(3) generations.

Differential Nutritional Requirements for Reproduction of Two Strains of Caenorhabditis Elegans in Axenic Culture

Caenorhabditis elegans (Maupas) ist eine selbstbefruchtende protandrische zweigeschlechtliche Art. Zwei Varietaten von verschiedenen geographischen Gebieten, die als Bergerac und Bristol nach ihren Herkunftsgebieten benannt werden, wurden isoliert. Es wurden Unterschiede in ihren Nahrungsanspruchen gefunden, wie durch den Entwicklungsumfang ihrer Kulturen in verschiedenen Nahrboden bewiesen werden konnte.