Figure 2.

(a) Map of all mutation pairs (small dots) and those showing antagonistic epistasis (large dots) for PSTVd. (b) Same but for PLMVd. White dots indicate strictly compensatory mutations (i.e., baseparing is restored in the double mutant) and fall nearly exclusively in the reverse diagonal. Semifilled dots are cases of broad-sense compensatory mutations (the effect of the double mutant on folding stability is smaller than the effect of at least one of the single mutations), whereas filled dots are noncompensatory antagonistic pairs. Taken from [20].