Thermodynamic framework accurately predicts the sign of epistasis and its environment dependence for a canonical cis-regulatory element.

Drug resistance in HIV is the result of mutations, which affect fitness depending on epistatic interactions with the entire sequence background that varies within and between patient populations.

Experimental mapping of the joint sequence space of an ancient transcription factor (TF) and its DNA binding sites reveals that epistasis across the molecular interface permitted the evolution of a new and specific TF-DNA complex.

Greater phenotypic variation is exposed by mutations in a gene regulatory system compared to mutations in its constitutive components, namely the transcription factor and the promoter, alone.

Some of the mutations that occur during influenza evolution can only be tolerated in conjunction with other mutations that increase the stability of a viral protein.

Genome engineering and phenotyping in vivo reveal surprising new features of adaptive amino acid substitutions that were previously inaccessible.

Pairwise combinations of growth-promoting genes regulating distinct cellular mechanisms lead to synergistic effects on leaf growth, and hence greatly increased leaf size.

Rectangular order perturbations generalize sign epistasis, capture global aspects of fitness landscapes, and clarify how rank order approaches relate.

Variable petal number in Cardamine hirsuta is explained by regulatory changes in the MADS-box gene APETALA1 that relaxed its epistasis over mapped QTL in the C. hirsuta genome.