Gene body methylation buffers noise in gene expression in plants

Non-genetic variability in gene expression is an inevitable consequence of stochastic nature of processes driving transcription and translation. Largely thought to be deleterious to cell fitness, it is not uniform across the transcriptome. This implies the existence of (molecular) determinants affecting the degree of gene expression variability, although this remain poorly understood in multicellular systems. In this study, we found a link between gene body methylation and noise in gene expression in Arabidopsis thaliana . More specifically, genes with high levels of noise show low levels of gene body methylation, while genes with lower level of noise in gene expression show higher level of gene body methylation. Most importantly, loss of CpG methylation in gene bodies lead to a significant number of genes displaying higher noise in gene expression. This could be compensated by low but significant gain of non-CpG methylation at promoters of certain genes. Overall, our results show that gene body methylation has a functional role and specifically controls the noise in gene expression for a large number of genes.