Changes of gene expression but not cytosine methylation are associated with male parental care reflecting behavioural state, social context, and individual flexibility

Abstract

Behaviour is often a front line response to changing environments. Recent studies show behavioural changes are associated with changes of gene expression; however, these studies have primarily focused on discrete behavioural states. We build on these studies by addressing additional contexts that produce qualitatively similar behavioural changes. We measured levels of gene expression and cytosine methylation, which is hypothesized to regulate the transcriptional architecture of behavioural transitions, within the brain during male parental care of the burying beetle Nicrophorus vespilloides in a factorial design. Male parenting is a suitably plastic behaviour because although male N. vespilloides typically do not provide direct care (i.e. feed offspring) when females are present, levels of feeding by a male equivalent to the female can be induced by removing the female. We examined three different factors: behavioural state (caring versus non-caring), social context (with or without a female mate) and individual flexibility (if a male switched to direct care after his mate was removed). The greatest number of differentially expressed genes were associated with behavioural state, followed by social context and individual flexibility. Cytosine methylation was not associated with changes of gene expression in any of the factors. Our results suggest a hierarchical association between gene expression and the different factors, but that this process is not controlled by cytosine methylation. Our results further suggest that the extent a behaviour is transient plays an underappreciated role in determining its underpinning molecular mechanisms.

Evolved changes in DNA methylation in response to the sustained loss of parental care in the burying beetle

“…So while the initial response to the removal of care involves differential methylation in stress-related pathways, evolved differential methylation is enriched in processes associated with growth and brain development though this was not always associated with gene expression at the developmental point at which we measured it. DNA methylation in insects, including the burying beetle, appears to be stable across the lifespan (Cunningham et al, 2019; Yagound et al, 2020). This raises the possibility that DNA methylation may be a product of ancestral transcriptional states.…”

Predictable gene expression related to behavioral variation in parenting

“…Mean and standard deviation of parenting was 11.67 ± 8.33 observations of feeding for the low group and 72.42 ± 2.18 observations of feeding for the high group, indicating substantial quantitative behavioral differences (Benowitz et al 2016b). We analyzed head tissue, which contains both brain and fat body, following previous studies that identified differential expression of genes associated with parenting in females (Parker et al 2015;Cunningham et al 2014Cunningham et al , 2016Cunningham et al , 2019Roy-Zokan et al 2015;Benowitz et al 2017a,b). We performed phenolchloroform extractions using Qiagen RNeasy Lipid Kits (Qiagen, Venlo, Netherlands) and synthesized cDNA using qScript (Quantabio, Beverly, MA) reverse transcriptase (Parker et al 2015;Roy-Zokan et al 2015).…”

“…Reflecting this, an RNA-seq study comparing non-parenting and parenting individuals identified broad transcriptional differences (> 700 genes) between the two states (Parker et al 2015). Transcriptional differences have also been defined for responses to social context and for plasticity in male parenting (Cunningham et al 2019). Thus, we have a clear phenotype with well characterized DE associations.…”

Functional genomics of parental care of insects

“…They found ~550, ~100, and ~20 genes associated with these variables, respectively, showing the greatest influence is from behavior. Biological function of these genes was associated with metabolism (Cunningham et al, 2019).…”