Evolution of the ONSEN retrotransposon family activated upon heat stress in Brassicaceae.

A Ty1/Copia-like retrotransposon, ONSEN, is activated by heat stress in Arabidopsis thaliana, and its de novo integrations that were observed preferentially within genes implies its regulation of neighboring genes. Here we show that ONSEN related copies were found in most species of Brassicaceae, forming a cluster with each species in phylogenetic tree. Most copies were localized close to genes in Arabidopsis lyrata and Brassica rapa, suggesting conserved integration specificity of ONSEN family into genic or open chromatin. In addition, we found heat-induced transcriptional activation of ONSEN family in several species of Brassicaceae. These results suggest that ONSEN has conserved transcriptional activation promoted by environmental heat stress in some Brassicaceae species.