Strength of purifying selection on the amino-acid sequence is associated with the amount of non-additive variance in gene expression

AbstractContemporary populations are unlikely to respond to natural selection if much of their genetic variance is non-additive. Understanding the evolutionary and genomic factors that drive amounts of non-additive variance in natural populations is therefore of paramount importance. Here, we use a quantitative genetic breeding design to delineate the additive and non-additive components of expression variance of 17,656 gene transcripts segregating in the outcrossing plantArabidopsis lyrata. We find that most of the genetic variance in gene expression represents non-additive variance, especially among long genes or genes involved in epigenetic gene regulation. Genes with the most non-additive variation not only display a markedly lower rate of synonymous variation, they have also been exposed to stronger purifying selection than genes with high additive variance. This study demonstrates that the potential of standing variation for future evolution is shaped the history of purifying selection.