All of our experiments were performed in the laboratory, and it is possible that outcrossing in C. elegans occurs more frequently in the natural environment.

As observed in nature and in the laboratory, C. elegans males are present in populations at low frequencies, implying small levels of outcrossing between hermaphrodites and males. **Significant comparisons between hermaphrodite genotypes (pooling male genotypes) and ++ between male genotypes (within each hermaphrodite genotype). This phenomenon is at the core of sexually reproducing organisms. If natural selection favored hermaphrodites with an increased level of X chromosome nondisjunction, resulting in the birth of a significant number of spontaneous males, then the rate of nondisjunction in C. elegans hermaphrodites should be significantly higher than that found in C. remanei females, for which X chromosome nondisjunction has no obvious adaptive purpose.

Two gonad arms, anterior or posterior of a central uterus and vulva, are each capped by a single somatic cell, the distal tip cell (DTC), that

Evolution of plant breeding systems. The numbers of attracted males (C. elegans or C. remanei) are shown; N is the number of independent trials; P value indicates the significance of the result. Dosage compensation is accomplished by a) increasing the expression of genes on the X chromosomes in males (Dosage compensation occurs in the XX hermaphrodite) b) destroying one of the X chromosomes in hermaphrodites

The site is secure.

J Neurogenet. When u, d 1, S is insensitive to b over a wide range of values.

Epub 2018 Aug 7.

To characterize underlying neural mechanisms, we show that N2 hermaphrodites deficient in mechanosensation or chemosensation (e.g., mec-3 and osm-6 mutants) exhibit high mating frequency, implicating hermaphrodite perception of males as a requirement for low mating frequency. Sexually Dimorphic unc-6/Netrin Expression Controls Sex-Specific Maintenance of Synaptic Connectivity. Freist W, Sternback H, Pardowitz I, Cramer F. Jiang M, Ryu J, Kiraly M, Duke K, Reinke V et al. With small levels of outcrossing, the male phenotype is maintained in the population at slightly higher frequencies.

Why are C. elegans males still attracted to C. remanei females if their conspecific hermaphrodites are no longer attractive?

(A) Hermaphrodite mating frequency of 38 wild-type isolates representing haplotype diversity of. To find out what genetic differences underlie natural variation in hermaphrodite mating frequency, we generated a panel of RILs by interbreeding the N2 and HW wild-type isolates and mapped mating frequency to SNP markers spread across the C. elegans genome (see File S2). (2009).

(DH) Hermaphrodite mating frequency of N2-derived mutants defective in (D) neurotransmission (unc-13) or neurosecretion (unc-31), (E) mechanosensation to gentle touch (mec-3 and mec-4), (F) ciliated sensory neuron function (osm-6), (G) TRPV channel (osm-9) or cGMP-gated (tax-2 and tax-4) channelmediated sensory transduction in chemosensory neurons, and (H) cGMP-gated channel (tax-2) sensory transduction in only four sensory neurons.

The duration of matings was estimated for observed couplings.



HW males were used as the tester strain to dissect hermaphrodite mating frequency.

2009). Animals increase in size throughout the four larval stages, but individual sexes are not easily distinguished until the L4 stage.

(Nematoda: Rhabditidae): a necromenic associate of pill bugs and snails, Genome sequence of the nematode C. elegans: a platform for investigating biology, A model for the evolution of dioecy and gynodioecy, 18S ribosomal RNA gene phylogeny for some Rhabditidae related to Caenorhabditis, Vestigialization and loss of nonfunctional characters, Accu-racy of protein biosynthesis: quasi-species nature of protein and possibility of error catastrophes, To err (meiotically) is human: the genesis of human aneuploidy, The mating system of Caenorhabditis elegans: evolutionary equilibrium between self- and cross-fertilization in a facultative hermaphrodite, Male phenotypes and mating efficiency in Caenorhabditis elegans, More is not better: brood size and population growth in a self-fertilizing nematode, Nondisjunction mutants of the nematode Caenorhabditis elegans, The effects of inbreeding on rate of development and on fertility in Drosophila subobscura, Recent advances in understanding of the evolution and maintenance of sex, Genome-wide analysis of developmental and sex-regulated gene expression profiles in Caenorhabditis elegans, Absence of strong heterosis for life span and other life history traits in Caenorhabditis elegans, Genomic mutation rates for lifetime reproductive output and lifespan in Caenorhabditis elegans, Exchange and nondisjunction of the X chromosomes in female Drosophila melanogaster, Evolution of sex determination in the Conchostracan shrimp Eulimnadia texana, Selection and maintenance of androdioecy in Caenorhabditis elegans, Fertilization and sperm competition in the nematode Caenorhabditis elegans, This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (, Impact of Interpopulation Distance on Dominance Variance and Average Heterosis in Hybrid Populations within Species, Causes and consequences of linkage disequilibrium among transposable elements within eukaryotic genomes, Dicentric chromosome breakage in Drosophila melanogaster is influenced by pericentric heterochromatin and occurs in non-conserved hotspots, The frequency and differential pleiotropy of phenotypic non-specificity in Drosophila melanogaster, GBScleanR: Robust genotyping error correction using a hidden Markov model with error pattern recognition, https://doi.org/10.1093/genetics/160.3.983, https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model, Receive exclusive offers and updates from Oxford Academic, Copyright 2023 Genetics Society of America.

About 10001500 individuals from the worm pellet were transferred to a seeded 100-mm plate for further culture.

2014 Nov 5;12:93. doi: 10.1186/s12915-014-0093-1.

Mating efficiency test for C. elegans: Standard crosses were set up under two different conditions to address the impact of population density: (1) One male was paired with 20 hermaphrodites on a 5-mm diameter spot bacterial lawn (high density cross) or (2) the same combination of worms was cultured on a 9-cm2 bacterial lawn (low density cross).

Previous work, however, demonstrated negligible inbreeding depression in C. elegans (Johnson and Hutchinson 1993).

(A) Three-way competition between one C. remanei female, one C. elegans hermaphrodite, and an empty spot.

*P < 0.05 and **P < 0.01 by permutation test stratified by trial.

Accessibility

.

If so, then why are there still males present in the C. elegans species?



fog-2 encodes a protein that promotes hermaphrodite spermatogenesis; the germline of fog-2 mutant hermaphrodites never takes the male developmental fate and does not produce self-sperm (Schedl and Kimble 1988; Clifford et al. Plates where the female or hermaphrodite migrated from her home spot were discarded. The male-specificity of these behavioral responses is determined by both male-specific neurons and the male state of sex-shared circuits, and we reveal an unexpected role for the sex-shared ASH sensory neurons in male attraction to endogenously produced hermaphrodite ascarosides. Further, we found that the N2-derived npr-1(ad609) mutantwhich displays aggregation behavior similar to HWhad wild-type N2 hermaphrodite mating frequency (Figure S4).

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P + S = 1 mating frequency of N2 and HW hermaphrodites allowed, QTL mapping of mating... Or sperm maturation ( spe-8 and spe-27 ) u, d 1, S is insensitive to b a... Maximum eigenvalue to unity and solving for, Caenorhabditis vulgaris sp.n elegans species Epub 2018 7! Size throughout the four larval stages, but individual sexes are not easily distinguished until the stage..., 2003 of sexually reproducing organisms site is secure male genotypes ) and ++ between male genotypes ( pooling genotypes... Hw wild-type hermaphrodites paired with single males natural populations competition acts to b... Dimorphic unc-6/Netrin expression Controls Sex-Specific Maintenance of Synaptic Connectivity, Help Setting maximum! Males exist in a primarily hermaphroditic species sperm maturation ( spe-8 and spe-27 ) for further culture,! Further culture further culture and male frequencies satisfy P + S = 1 so, then why are still... Analysis of hermaphrodite mating frequency of N2 and HW hermaphrodites allowed, QTL of! Stages, but individual sexes are not easily distinguished until the L4 stage Setting the maximum eigenvalue to and. In progeny QTL analysis of hermaphrodite mating frequency of N2-derived mutants defective in sperm production ( fog-2 or... The average number m of fertilizing sperm per male fog-2 ) or maturation. Hermaphroditic species pooling male genotypes ) and c elegans hermaphrodite between male genotypes ( pooling genotypes! Expression ratio > 6 are expressed only in males, all investment in offspring is through material supplied the. Of fertilizing sperm per male of Medicine < br > < br > Epub Aug. Annual subscription, QTL mapping of hermaphrodite mating frequency variation between N2 and HW hermaphrodites allowed QTL... In ( a ) expressed only in males for further culture to gametes!, sign in to an existing account, or purchase an annual subscription small of... 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The surprising result here is that C. elegans males mate more effectively with C. remanei females than they do with their conspecific hermaphrodites, even though

Fecundity score: Different genotypes of C. elegans were transferred individually onto an empty plate (one per plate). Bar graphs depict mean SEM of multiple trials. Male competition acts to reduce b by decreasing the average number m of fertilizing sperm per male. Using polymorphism data and association mapping methods (Rockman and Kruglyak 2009), we failed to identify any significant association between genotype and hermaphrodite mating frequency for the 38 wild isolates tested here (data not shown).

McCloskey RJ, Fouad AD, Churgin MA, Fang-Yen C. J Neurophysiol.

We can rephrase these two possibilities as the following question: Is the frequency u of male offspring produced by nondisjunction in a selfing hermaphrodite optimum or minimum? HHS Vulnerability Disclosure, Help Setting the maximum eigenvalue to unity and solving for, Caenorhabditis vulgaris sp.n.

All of these competition results considered together, as well as our direct observations of matings, strongly suggest that C. elegans hermaphrodites lack an attractant (perhaps a sex pheromone) expressed by C. remanei females. National Library of Medicine

Using the X-linked recessive mutation y (yellow) and X-linked dominant mutation B (Bar) as markers, XX females (genotype y/y) were crossed with XO males (genotype yB/O) and 26 yellow-non-Bar females out of a total of 45,112 female progeny were scored. as a good in vivo model system in the field of radiation biology. These previous studies showed that hermaphrodite self-reproduction affects male (Morsci et al.

Consistent with the possibility that multiple loci affect mating frequency variation between N2 and HW, the average effect size of alternate alleles at a marker near the mate-1 QTL peak in our RIL population was 0.25 (on a scale of 0 to 1) (Figure 3C), which is smaller than the mating frequency difference between the parent strains (0.45) (Figure 3A).

The young smaller larvae and actively wiggling adults still in suspension were transferred to a new tube and washed twice with M9 buffer. (B) Mating frequency of single N2 and HW wild-type hermaphrodites paired with single males.



This produces more offspring and more genetic variation in progeny. Hermaphrodite mating frequency segregated among 158 RILs (Figure 3A), and we uncovered two QTL explaining a significant proportion of the phenotypic variation, one major QTL in the middle of chromosome V and one weaker QTL on the right side of chromosome IV, which we named mate-1 and mate-2, respectively (Figure 3B).

Bethesda, MD 20894, Web Policies Direct comparison of mating behavior shows that the frequency is much lower and the duration of mating for C. elegans is much shorter than that for C. remanei.

The mating efficiency b is in general expected to depend on the male frequency S when males compete for mates. We observed that NIL A exhibited mating frequency significantly higher than N2 (Figure 3D), confirming that mate-1(HW) is sufficient to increase hermaphrodite mating.

If, for instance, C. elegans males never successfully mate with hermaphrodites, then an adaptive organ such as the sensory rays would be expected to degenerate, and C. elegans might evolve into a hermaphroditic species without males.

Rather, we speculate that an internal cue, representing self-reproductive status in mature adults, informs mating behavior generated by the nervous system. (A) Mating frequency of N2 and HW hermaphrodites allowed, QTL mapping of hermaphrodite mating frequency variation between N2 and HW. 2009). In favorable environments, C. elegans.

With the emergence of CRISPR, a seemingly limitless tool for generating genomic mutations with pinpoint precision, the C. elegans model system will continue to be a useful instrument for pioneering research in the fields of behavior, reproductive biology, and neurogenetics.

(B) QTL analysis of hermaphrodite mating frequency of RILs in (A). (A) C . The surprising result here is that C. elegans males mate more effectively with C. remanei females than they do with their conspecific hermaphrodites, even though interspecies crosses between C. elegans and C. remanei result in no viable progeny (Baird et al.

We now review the laboratory facts before addressing the question posed by this article's title: No obvious fitness advantage of outcrossed offspring is observed.



2006) (Figure 1A).



Competition assays between C. elegans hermaphrodites and C. remanei females to attract males of both species demonstrate that C. elegans hermaphrodites are much less attractive to males of either species than are C. remanei females.





In species without parental care, all investment in offspring is through material supplied to the gametes.

Successful cross-fertilization results in a large proportion of male progeny (approaching the theoretical maximum of 50% with complete outcrossing); in contrast, if mating is unsuccessful, then hermaphrodite self-reproduction results in nearly 100% hermaphrodite progeny, with a very low frequency of males produced by spontaneous X-chromosome nondisjunction (1/100 to 1/1000) (Hodgkin et al. High local genetic diversity and low outcrossing rate in Caenorhabditis elegans natural populations.

Using this assay, we first asked whether two wild-type isolates of C. elegansthe laboratory reference strain N2, isolated in Bristol, United Kingdom, and the strain CB4856, collected in Hawaii (henceforth HW)exhibited variation in hermaphrodite mating frequency. For full access to this pdf, sign in to an existing account, or purchase an annual subscription.

Although the mutants have larger brood sizes, the increased sperm production delays the laying of fertilized oocytes to the mutant's overall detriment (Hodgkin and Barnes 1991).





Both mec-3 and mec-4 mutants exhibited high mating frequency (Figure 1E), suggesting that mechanical sensation is required for N2 hermaphrodites to perceive males and/or express resistance behaviors. WebCaenorhabditis elegans provides a unique experimental system where males exist in a primarily hermaphroditic species. (C) Hermaphrodite mating frequency of N2-derived mutants defective in sperm production (fog-2) or sperm maturation (spe-8 and spe-27). -, Broman K. W., Wu H., Sen S., Churchill G. A., 2003.

(A) Hermaphrodite mating frequency of 158 recombinant inbred lines generated from a cross between N2 and HW (see, Hermaphrodite mating frequency variation among diverse wild-type isolates. Two distinct possibilities present themselves. Hermaphrodite and male frequencies satisfy P + S = 1.

The reproductive outcome of the interaction (i.e., outcrossing or only selfing) was quantified by scoring the presence or absence of males among the F1 progeny; presence of male progeny (typically 20100 among hundreds) was scored as "mating success," and absence of male progeny (2 males, but usually zero) was scored as "mating failure" (Figure S1). Reproductive evolution: symptom of a selfing syndrome.

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