Genome methylation patterns across castes and generations in a parasitoid wasp

Abstract

Environmental influences shape phenotypes within and across generations, often through DNA methylations that modify gene expression. Methylations were proposed to mediate caste and task allocation in some eusocial insects, but how an insect's environment affects DNA methylation in its offspring is yet unknown. We characterized parental effects on methylation profiles in the polyembryonic parasitoid wasp Copidosoma koehleri, as well as methylation patterns associated with its simple caste system. We used methylation‐sensitive amplified fragment length polymorphism (MS‐AFLP) to compare methylation patterns, among (1) reproductive and soldier larvae; and (2) offspring (larvae, pupae, and adults) of wasps that were reared at either high or low larval density and mated in the four possible combinations. Methylation frequencies were similar across castes, but the profiles of methylated fragments differed significantly. Parental rearing density did not affect methylation frequencies in the offspring at any developmental stage. Principal coordinate analysis indicated no significant differences in methylation profiles among the four crossbreeding groups and the three developmental stages. Nevertheless, a clustering analysis, performed on a subset of the fragments, revealed similar methylation patterns in larvae, pupae, and adults in two of the four parental crosses. Nine fragments were methylated at two cytosine sites in all larvae, and five others were methylated at two sites in all adults. Thus, DNA methylations correlate with within‐generation phenotypic plasticity due to caste. However, their association with developmental stage and with transgenerational epigenetic effects is not clearly supported.

Dynamic changes in DNA methylation during postnatal development in zebra finches Taeniopygia guttata exposed to different temperatures

“…While MS‐AFLP proved an adequate technique to investigate DNA methylation changes in post‐hatch zebra finches, the technique is limited in its ability to provide information about the sequence and function of methylated loci (Fulneček and Kovařík ). Consequently, correlations between the methylation patterns observed in our study, and their phenotypic effects are yet to be elucidated (Shaham et al ). It would be useful for future work to focus on next‐generation sequence‐based techniques, such as bisulfite sequencing (Bentz et al , Lea et al , Weyrich et al ).…”

Methylation and gene expression differences between reproductive and sterile bumblebee workers

“…A major finding was that silencing of the Dnmt3 gene (involved in methylation establishment) in larvae produced queens rather than workers (Kucharski et al 2008). DNA methylation has also been linked with alternative splicing differences between castes in two ant species (Bonasio et al 2012) and is thought to be involved in caste determination in Copidosoma koehleri, a species of primitively social wasp (Shaham et al 2016). However, it is clear DNA methylation is not a conserved mechanism in Hymenoptera for caste differentiation.…”

“…) and is thought to be involved in caste determination in Copidosoma koehleri , a species of primitively social wasp (Shaham et al. ). However, it is clear DNA methylation is not a conserved mechanism in Hymenoptera for caste differentiation.…”

The Importance of Validating the Demethylating Effect of 5-aza-2′-deoxycytidine in Model Species

“…Here we want to emphasize the importance of validating the demethylating effect of 5-aza-dC when testing hypotheses about the relationship between DNA methylation and phenotypic expression. In addition to sex allocation (Cook et al 2015) and induction of diapause (Pegoraro et al 2016), several other phenotypes have been implied in parasitoid wasps to be regulated epigenetically, including caste determination (Shaham et al 2016) and fatty acid composition (Sak 2017). For a more reliable interpretation of all experiments with orally administered 5-aza-dC to parasitoids, it will be necessary to have a better idea of the extent and pervasiveness of demethylating effect of this method.…”