Evolution of repeats and gene families in Brassicaceae species of varied climates

On large-scale temperature gradients such as over elevation or latitude, species turnover is common and specialists exist often at the most extreme points. This is likely paralleled by adaptive and possibly also non-adaptive changes on a molecular level, from genes to the structure of genomes. Here we investigated for associations between both elevation and latitude with features of the genome including genome size, transposable element (TE) content and gene family expansion and contraction by comparative genomics using the plant family Brassicaceae with established reference genomes. We found that species of cooler climates and higher elevation (decoupled from temperature) had larger genomes with higher TE contents, particularly long terminal repeat elements (LTR), as well as those of warm climates, explaining about 25% of variation. This hints towards either a selective advantage of larger genomes and higher TE abundance or a failure of TE silencing in extreme environments. Gene family expansions and contractions in species of high elevations highlighted a restructured genomic architecture regarding cell wall modeling, the innate immune system and processes involved in posttranslational protein modi?cations. Results point to considerable parallel evolution of genome size and genome structure as well as the size of some gene families in response to species establishing in distinct geo-climatic regions.