Meeting Abstract
The likeness of gene regulation to a light switch— either turned on or off— is considered instructive but overly simplistic. There is however an epigenetic element that operates in this simple binary fashion. In invertebrates, DNA methylation divides genes into just two categories—a strongly and weakly methylated set. What, if any, is the adaptive significance of this division? In this study, we combine methylome sequencing (MBD-seq), RNA-seq, and an evolutionary analysis of 20 anothozoan transcriptomes to characterize the transcriptional and evolutionary nature of these two categories. As seen in insect models, expression of strongly methylated genes tends toward spatial and temporal stability, akin to ‘housekeeping genes’ described in microbes. In contrast, expression of weakly methylated genes tends to be flexible across time, space, and environment. Strongly methylated genes also evolve slowly, displaying categorically lower rates of nonsynonymous (dN) and synonymous substitutions (dS). Strong methylation also correlates with codon bias, suggesting that lower dS may result from selection for optimal codons in these widely and stably expressed genes. Together these results bolster our understanding of gene body methylation as a signature of transcriptional and evolutionary stability.
