Epigenetic regulation of sex ratios may explain natural variation in self-fertilization rates

Abstract

Self-fertilization (selfing) favours reproductive success when mate availability is low, but renders populations more vulnerable to environmental change by reducing genetic variability. A mixed-breeding strategy (alternating selfing and outcrossing) may allow species to balance these needs, but requires a system for regulating sexual identity. We explored the role of DNA methylation as a regulatory system for sex-ratio modulation in the mixed-mating fish Kryptolebias marmoratus. We found a significant interaction between sexual identity (male or hermaphrodite), temperature and methylation patterns when two selfing lines were exposed to different temperatures during development. We also identified several genes differentially methylated in males and hermaphrodites that represent candidates for the temperature-mediated sex regulation in K. marmoratus. We conclude that an epigenetic mechanism regulated by temperature modulates sexual identity in this selfing species, providing a potentially widespread mechanism by which environmental change may influence selfing rates. We also suggest that K. marmoratus, with naturally inbred populations, represents a good vertebrate model for epigenetic studies.

DNA methylation in adults and during development of the self‐fertilizing mangrove rivulus, Kryptolebias marmoratus

“…Thus, Ellison et al. () suggested that natural variation in self‐fertilization rates among populations might be explained through epigenetic regulation (DNA methylation) of sex ratios.…”

Local parasite pressures and host genotype modulate epigenetic diversity in a mixed‐mating fish

“…Using data from all sampling sites, we found that genome‐wide DNA methylation was strongly influenced by selfing lineage, and only at a smaller scale by inbreeding through its interaction with selfing lineage (Bell et al, ; Bjornsson et al, ; Dubin et al, ; Gertz et al, ). Strong epigenetic differences between selfing lines had been identified previously in K. marmoratus (Berbel‐Filho et al, ; Ellison et al, ), indicating an important role of the genetic background in the epigenetic variation of mangrove killifishes. In addition, we also found a significant correlation between DNA methylation and genetic variation (at both AFLP and microsatellites data), suggesting that autonomous variation in DNA methylation may be limited (Dubin et al, ).…”

“…A DNA aliquot of 100 ng per individual was split for digestion with two enzyme combinations: EcoRI/HpaII and EcoRI/MspI. The digested DNA was ligated to adaptors, and a selective PCR was conducted using the primers ECORI‐ACT: GACTGCGTACCAATTCACT and HPA‐TAG: GATGAGTCTAGAACGGTAG following Ellison et al (). The HpaII primer was end‐labeled with 6‐FAM.…”

Epigenetic‐induced alterations in sex‐ratios in response to climate change: An epigenetic trap?

“…In this sense, our own work suggests that temperature‐related variation in the sex‐ratio of the self‐fertilizing fish Kryptolebias marmoratus is related to changes in methylation patterns between males and hermaphrodites. We examined methylation in the brain of males and hermaphrodite fish incubated at different temperature as embryos and found that methylation of at least two genes ( cyp19a , sox9a ) could be involved in modulating K. marmoratus sex‐ratios in response to environmental change during embryo development . As for other fish species, we found that the variation in proportion of males occurring with temperature change seems to be the result of the influence of environmental and genetic factors in sex regulation .…”