The genomic determinants of genotype × environment interactions in gene expression

• Genotype × environment (G×E) interactions in gene expression levels are ubiquitous.
• Genomic biases influence the appearance of G×E interactions.
• Genes with changed expression across genotypes tend to also have G×E interactions.
• GxE interactions may provide the required variation for genetic assimilation.

Predicting phenotype from genotype is greatly complicated by the polygenic nature of most traits and by the complex interactions between phenotype and the environment. Here, we review recent whole-genome approaches to understand the underlying principles, mechanisms, and evolutionary impacts of genotype × environment (G×E) interactions, defined as genotype-specific phenotypic responses to different environments. There is accumulating evidence that G×E interactions are ubiquitous, accounting perhaps for the greater part of the phenotypic variation seen across genotypes. Such interactions appear to be the consequence of changes to upstream regulators as opposed to local changes to promoters. Moreover, genes are not equally likely to exhibit G×E interactions; promoter architecture, expression level, regulatory complexity, and essentiality correlate with the differential regulation of a gene by the environment. One implication of this correlation is that expression variation across genotypes alone could be used as a proxy for G×E interactions in those experimental cases where identifying environmental variation is costly or impossible.