Evolutionary and functional importance of simple repeats in 1135 Arabidopsis thaliana genomes

The predominant view in biology has been that genetic variation caused by point mutations are the main source for evolutionary change. Yet, point mutations alone cannot account for the genetic variation necessary to deal with rapid environmental changes. Genes and promoters are enriched with the tandem repeats (TRs), which are sets of trinucleotides repeated in tandem and that can mutate 10 to 100 000 times faster than point mutations. A working hypothesis is that such sequences serves as evolutionary hotspots that facilitate adaptation by fine-tuning gene function. To test this hypothesis, we are surveying the repeat length variation present in genes from more than a thousand Arabidopsis individuals spread mainly across the northern hemisphere. We are exploring associations between repeat length variation and ecological clines, such as variation in temperature and precipitation. We will investigate the functional importance of the repeat lengths in a set of candidate genes, representing the variation observed in the wild, by introducing them into Arabidopsis and monitoring phenotypic changes at the molecular and morphological level. We will further expose the Arabidopsis plants to various physical and biological stress, and screen for phenotypic and genetic changes relating to trinucleotide TRs.