Ccorrelated gene expression shifts characterise the repeated evolution of zinc-tolerance in Silene uniflora.

Recent anthropogenic changes have prompted rapid evolution in plants, but whether these occur via predictable mechanisms remains unclear. Gene expression changes are known to underpin local adaptation in many systems, but whether the degree to which changes occur repeatedly across instances of parallel rapid adaptation is still poorly understood. In this study, we investigated whether the independent evolution of zinc-tolerant populations of Silene uniflora on geographically distant abandoned mines has involved parallel changes gene expression. We compared root gene expression profiles, under both control and zinc-contaminated conditions, of two zinc-tolerant populations and their nearest zinc-sensitive sister populations. In the absence of zinc, highly overlapping sets of genes were differentially expressed between ecotypes. In tolerant populations, some genes show closely correlated responses to zinc-contamination, even after accounting for genes with expression changes across all populations that can be linked to the general stress response. Furthermore, for genes with derived expression changes in both mine populations, the expression level in one population is highly predictive of the level in the other, particularly in the zinc-contaminated treatment. These results demonstrate that the identity of genes undergoing expression changes during repeated, rapid evolution to a specific environment is predictable, as is the quantitative response and expression level of these genes as well.