Natural Variation and Copulatory Plug Formation in Caenorhabditis elegans

Abstract

Most of the available natural isolates of the nematode Caenorhabditis elegans have been examined and compared with the standard laboratory wild type (Bristol N2). Molecular markers, in particular transposon restriction fragment length polymorphisms, were used to assign these isolates to 22 different races, for which brood size and spontaneous male frequency were determined. Several distinctive traits were observed in some of these races. One example is mab-23, in a race from Vancouver, which leads to severe distortion of male genitalia and prevents male mating. Another is gro-1, segregating in a Californian race, which is associated with slow growth, heat resistance and longevity. Many races differ from N2 in carrying a dominant allele at the plg-1 locus, causing copulatory plug formation by males. Properties and possible advantages of the plugging trait have been investigated. The dominant plg-1 allele does not lead to increased male mating efficiency, but males from a Stanford race (CB4855), in which the plugging trait was first observed, are much more virile than N2 males. Crosses between N2 and CB4855 indicate that the higher virility is due to multiple factors. Size differences between N2 and CB4855 are associated with factors mapping to LGV and LGX.

npr-1 Regulates Foraging and Dispersal Strategies in Caenorhabditis elegans

“…Individuals from the DA650, DA508, and DA609 strains also showed high dispersal propensity compared to N2 (Figure S5). These data were collected on hermaphrodites, which make up the majority (90%-99.9%) of C. elegans populations [1,16]. Unlike male mate searching [15], the hermaphrodite dispersal behavior reported here depends on the presence of food in the vicinity of the source patch (data not shown).…”

“…Variation at the npr-1 locus is perfectly correlated with the occurrence of gregarious and solitary feeding among 17 wild C. elegans isolates from around the world [1,2]. Both 215F and 215V alleles were recovered from a single sample in Pasadena (CA) and from independent samples collected 6 months apart at the same site in Altadena (CA) [1,2], indicating that there is a world-wide polymorphism at the locus. How is the npr-1 polymorphism maintained?…”

“…Wild isolates of Caenorhabditis elegans differ in their tendency to aggregate on food [1,2]. Most quantitative variation in this behavior is explained by a polymorphism at a single amino acid in the G protein-coupled receptor NPR-1: gregarious strains carry the 215F allele, and solitary strains carry the 215V allele [2].…”

Males, Outcrossing, and Sexual Selection in Caenorhabditis Nematodes

“…While ablation of mss function does not yield infertility, it does depress the ability of sperm cells to outcompete the sperm from other males for oocyte access in fertilization, and, impressively, experimental reintroduction of mss expression enhances sperm competitive ability (Yin et al 2018). The disrupted function of the plg-1 locus by a retroelement in many wild isolates of C. elegans also provides a well-characterized example of the consequences of male rarity through genetic disruption of a sex-specific gene (Hodgkin and Doniach 1997;Palopoli et al 2008). Deposition of a copulatory plug by males onto the vulva of their mate confers benefits to males in terms of fertilization assurance most strongly when females mate with multiple males, leading to selection conserving plugging in most species.…”

Shorter life and reduced fecundity can increase colony fitness in virtual Caenorhabditis elegans

“…When sperm are depleted, reproduction ceases. Reproduction can continue for a longer period if hermaphrodites mate with males (Hodgkin & Doniach, 1997; Hughes, Evason, Xiong, & Kornfeld, 2007); however, males are extremely rare in the wild (Schulenburg & Félix, 2017). The timing of the switch from sperm to oocyte production appears to be optimized to maximize population growth rate, balancing earlier onset of fertilization against greater sperm/progeny number (Hodgkin & Barnes, 1991).…”