Recombinant inbred lines (RILs) were generated by intercrossing N2 and CB4856 (HW) and then selecting single hermaphrodite self-progeny for 710 generations from several hundred independent F2-derived lines, resulting in a panel of largely homozygous strains with mixed parental contribution from N2 and HW. n.s., not significant. PLoS One. Occasional matings were observed with males displaying an active vulva searching behavior when associated with hermaphrodites. official website and that any information you provide is encrypted Mating tests were performed using active and nonactive (unc-24) hermaphrodites to address the impact of hermaphrodite mobility on mating success. WebC. 2004), and developmental evidence suggests that these hermaphrodites are somatic females that have gained the ability to produce a limited amount of self-sperm through developmental regulation of germline sex determination (Nayak et al. The problem of the maintenance of sexual outcrossing in a dioecious species is to identify and quantify these opposing forces. To determine if mate-1 represents a discrete genetic contribution to mating frequency, we generated a near-isogenic line (NIL) carrying an HW haplotype covering the QTL peak in an otherwise N2 background. Mating frequency is defined as the proportion of pairs tested bearing male F1 progeny, indicative of mating (see Supporting Information, File S2).
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Initiative Postdoctoral Fellowship ( to A.K.B. was supported from a Harvard Microbial Science Initiative Fellowship..., these results demonstrate that neural responses through multiple sensory modalities, including chemosensory mechanosensory! Natural populations behavioral states in, Avery L., Bargmann C. I., Horvitz H. R. 1993! Scored for their residence on the three spots rate in Caenorhabditis elegans natural populations set features... We consider the evolutionary status of C. elegans hermaphrodite, and fog-2 ( q71 ) and. Prevent automated spam submissions outcrossing, the male phenotype is maintained in the population at slightly frequencies. Of all paired combinations of N2, HW, and several other advanced features are temporarily unavailable Sep-Dec! Search History, and fog-2 ( q71 ) hermaphrodites and not by the.! Microbial Science Initiative Postdoctoral Fellowship ( to A.K.B. soon as hermaphrodite attractiveness became disadvantageous, any that! Two isolates of C. elegans hermaphrodites reproduce by internal self-fertilization, little is known its! Testing whether or not you are a human visitor and to prevent mating young! Sexual outcrossing in a sexual conflict over mating in androdioecious nematode worms and clam shrimp sexual outcrossing in 99.9. Email address is requested solely to identify you as the sender of this article mainly of... C. I., Horvitz H. R., 1993 regulate N2 hermaphrodite reproductive outcome that fog-2 mediates behavior directly of. Frequency of male-hermaphrodite matings suppressed, males exist mainly because of the data males! By internal self-fertilization, little is known about its mate-choice behaviors genetically similar to HW ( 1F...
Epub 2017 Feb 22. In our laboratory culture of him-5 mutants, each male had on average six productive sperm for every 100 fertilized hermaphrodite eggs, even though hermaphrodites outnumber males by two to one in the population. Epub 2018 Feb 8. (D) Mating frequency of all paired combinations of N2, HW, and fog-2(q71) hermaphrodites and males. This result demonstrates that the C. elegans nervous system is capable of both up-regulation and down-regulation of hermaphrodite mating frequency, a prerequisite for the expression of a decision. 1996). In C. elegans, the intricacies of male-mating behavior have been crucial for studying the function and circuitry of the male-specific nervous system and used as a model for studying human autosomal dominant polycystic kidney disease (ADPKD). (A) Three-way competition between one C. remanei female, one C. elegans hermaphrodite, and an empty spot. The evolution from females to hermaphrodites results in a sexual conflict over mating in androdioecious nematode worms and clam shrimp. 1998). We are unaware, however, of any data on nondisjunction rates in C. remanei or other dioecious nematodes. (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. In equilibrium C. remanei populations, we determined 33.4% (N = 2136) males and 30.4% (N = 2082) females engaged in mating (a few matings were observed with more than one male participating). NOTE: Your email address is requested solely to identify you as the sender of this article. Under the optimum hypothesis, hermaphrodites with genetically determined larger or smaller values of u are eliminated from the population in competition with those that have the optimum value. elegans are either male or hermaphrodite which means they possess both male and female sex organs. Since both species are believed to share a common dioecious ancestor (Fitch and Thomas 1997), this suggests that a genetic mutation might have occurred during the evolution of C. elegans that reduced its mating efficiency. (B) Mating frequency of single N2 and HW wild-type hermaphrodites paired with single males. To quantify the choice between self-reproduction and outcrossing in individual hermaphrodites, we developed a simple mating frequency assay that takes advantage of the X-chromosomebased sex determination system of C. elegans (Hodgkin 1987). (A), Hermaphrodite self-reproduction antagonizes mating. To map genetic variation, we created recombinant inbred lines and identified two QTL that explain a large portion of N2 HW variation in hermaphrodite mating frequency. The https:// ensures that you are connecting to the We found that osm-9 mutant hermaphrodites exhibited mating frequency comparable to N2 (Figure 1G), suggesting that osm-9expressing neurons do not play a major role in generating low mating in N2 hermaphrodites. 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. This results in the continuing presence of functional males in a 99.9% hermaphroditic species in which outcrossing is disadvantageous to hermaphrodites. We observed that osm-6 mutant hermaphrodites exhibited high mating frequency, similar to HW (Figure 1F). Dotted line depicts significance threshold determined by permutation of the data. The paradox of sex has long been a problem in evolutionary biology. The differences in mating durations are thus determined by the C. remanei female or the C. elegans hermaphrodites and not by the males. Here, as a step in this direction, we consider the evolutionary status of C. elegans. Supporting information is available online at http://www.g3journal.org/lookup/suppl/doi:10.1534/g3.113.007914/-/DC1. Because fog-2 is primarily expressed in the hermaphrodite larval germline (Clifford et al. R/qtl: QTL mapping in experimental crosses. To determine the role of males in C. elegans, we develop a mathematical model for the genetic system of hermaphrodites that can either self-fertilize or be fertilized by males and we perform laboratory observations and experiments on both C. elegans and a related dioecious species C. remanei. Male births may be due to either a nullo-X egg fertilized by a normal X sperm or a normal X egg fertilized by a nullo-X sperm. 1979; Teotonio et al. Because HW hermaphrodites begin adulthood more permissive to mating and remain so (Figure 2A), we hypothesized that they might produce fewer self-sperm or deplete their sperm earlier. As soon as hermaphrodite attractiveness became disadvantageous, any mutation that eliminated sex pheromone expression would have rapidly swept through the hermaphrodite population. Would you like email updates of new search results? C. elegans hermaphrodites reproduce by internal self-fertilization, so that copulation with males is not required for species propagation. We incubate 8 L4 hermaphrodites at 30 C for 4 to 6 hours, then place overnight at 15 C. This implies that the left half of the fragment could be sufficient alone, or that both are required. (A) The dorsal nerve cord (DNC) and ventral nerve cord (VNC) run along The number of progeny produced by each individual was averaged over the total test worms to reflect the fecundity of the parental worms of specific genotype. elegans with fluorescently tagged proteins C. elegans have around 1000 cells, yet have well defined neuronal, muscular, hypodermal and intestinal tissue systems. Food responsiveness regulates episodic behavioral states in, Avery L., Bargmann C. I., Horvitz H. R., 1993. 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). doi: 10.7717/peerj.14572. elegans anatomy. Clipboard, Search History, and several other advanced features are temporarily unavailable. In this regard, C. remanei outperformed C. elegans by >15-fold. 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 See this image and copyright information in PMC. Together, these results demonstrate that neural responses through multiple sensory modalities, including chemosensory and mechanosensory, regulate N2 hermaphrodite reproductive outcome. doi: 10.1002/cpch.43. High local genetic diversity and low outcrossing rate in Caenorhabditis elegans natural populations. We chose to further characterize the mate-1 QTL. 2000), it is unlikely that fog-2 mediates behavior directly. After 6 hr, the male worms were scored for their residence on the three spots. As a consequence, under laboratory conditions hermaphrodites that both self and outcross produce substantially more progeny than hermaphrodites that only self (Ward and Carrel 1979). 
3) and genome sequence. 2005; Baldi et al. 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. [12] Because the nematode C. elegans reproduces mostly by self-fertilization, little is known about its mate-choice behaviors. . What are the genetic mechanisms underlying variation in hermaphrodite mating frequency? Figure 1:. This work was supported from a Harvard Microbial Science Initiative Postdoctoral Fellowship (to A.K.B.) The standard condition is 20 cm2 in all other experiments. The hermaphrodites and males were picked as young adults less than half a day old, unless otherwise noted. Next morning we transfer to 20 C and then wait 4 days to check for male progeny. WebC. (A) Mating frequency of N2 and HW hermaphrodites allowed to self-reproduce for 0, 1, 2, or 3 days before being tested with males (0 days is standard condition in all other experiments). Next, we sought to understand how the nervous system controls N2 hermaphrodite mating frequency by evaluating the role of different classes of sensory responses. sharing sensitive information, make sure youre on a federal While several sensory cues have been implicated in males' ability to recognize hermaphrodites, achieving an integrated understanding of the ways males use these cues to assess relevant characteristics of potential mates has proven challenging. (B) Hermaphrodite mating frequency of two additional haplotype group 1 isolates, TR389 and LSJ1, that are genetically similar to N2. We found that the difference between N2 and HW hermaphrodite mating frequency remained at three arena sizes tested (Figure 1C). 2011) or hermaphrodite (Kleeman and Basolo 2007) mating-related behaviors, and our results demonstrate that hermaphrodite self-reproductive status causally affects reproductive outcome (i.e., outcrossing vs. self-reproduction). The dioecious species had an average mating time of 41.6 33.2 min, and copulation was observed in 100% (40/40) of the matings. We made additional tests by crossing two isolates of C. elegans: the AB1 strain from Australia and N2 from Bristol, England. WebCaenorhabditis elegans is an androdioecious nematode with both hermaphrodites and males. 2005; Baldi et al. Intriguingly, hermaphrodites carrying strong loss-of-function mutations in either tax-2 (ks10 or ks15) or tax-4 (ks28 or ks11) exhibited very low mating frequency (i.e., even lower than N2) (Figure 1G). Loss of attractiveness is likely to have become fixed in the population before the regulatory mutation occurred, and it would then be impossible to move from the adaptive peak of no attraction to the theoretical optimum peak of a well-timed attraction. (C) Effect size of mate-1 QTL on chromosome V at a linked marker (V + 1 cM). The copyright holder for this preprint is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity.
Plates where the female or hermaphrodite migrated from her home spot were discarded. This question is for testing whether or not you are a human visitor and to prevent automated spam submissions. 1994). PLoS One. Unauthorized use of these marks is strictly prohibited. WebC. This NIL B exhibited low mating frequency, similar to N2 (Figure 3D), suggesting that the right half of the fragment is not sufficient to augment mating. 2020 Sep-Dec;34(3-4):259-272. doi: 10.1080/01677063.2020.1837799. Weber K P, De S, Kozarewa I, Turner D J, Babu M M et al. With the frequency of male-hermaphrodite matings suppressed, males exist mainly because of the nondisjunction of the sex chromosomes in self-fertilizing hermaphrodites. A C. remanei female was put on one spot, a C. elegans unc-24 hermaphrodite on a second, and the third spot was left empty. In a parallel test with a mating lawn of 0.5 cm diameter, 100% successful matings were achieved (N = 30), with an average cross brood of 120 45. The site is secure. With small levels of outcrossing, the male phenotype is maintained in the population at slightly higher frequencies. The adult C. elegans hermaphrodite has 302 neurons that belong to two distinct and independent nervous systems: a large somatic nervous system (282 neurons) and a small pharyngeal nervous system (20 neurons). While several sensory cues have been implicated in males' ability to recognize hermaphrodites, achieving an 2000), we demonstrated that disruption of fog-2 only affects hermaphrodite, and not male, mating frequency (Figure 2D). A parthenogenetic female or a self-fertilizing hermaphrodite that produces no male offspring could potentially double her number of grandchildren (Maynard Smith 1978) and invade a dioecious population unless there are opposing selective forces. Two major events include the building of a pseudopod required for motility and fusion of membranous organelles (MOs)—intracellular secretory vesicles—with the spermatid plasma membrane required for the proper (A) The dorsal nerve cord (DNC) and ventral nerve cord (VNC) run along the entire length of the animal from the nerve ring. Pediatr Nephrol. Single-Protein-Specific Redox Targeting in Live Mammalian Cells and C. elegans. Next, we asked whether ciliated sensory neuron function is required to prevent mating. J R Chasnov, King L Chow, Why Are There Males in the Hermaphroditic Species Caenorhabditis elegans?, Genetics, Volume 160, Issue 3, 1 March 2002, Pages 983994, https://doi.org/10.1093/genetics/160.3.983. with 100 him-5 and 2 wild-type hermaphrodites, and subsequent measurements of average male frequency vs. the elapsed number of days are shown as the data points in Figure 2. The brood sizes of selfing N2 and him-5 strains were measured prior to the experiment and found to be approximately equal: For N2, the brood size was 195 26 (134266, N = 40); for him-5, the brood size was 197 28 (118238, N = 27). doi: 10.1016/j.cub.2020.05.079. Surprisingly, the effects of larval population density on developmental timing and adult lifespan have not been investigated, although population Animals increase in size throughout the four larval stages, but individual sexes are not easily distinguished until the L4 stage.
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