Analysis of SSR dynamics in chloroplast genomes of Brassicaceae family.

Simple sequence repeats (SSRs) are present abundantly in most eukaryotic genomes. They affect several cellular processes like chromatin organization, regulation of gene activity, DNA repair, DNA recombination, etc. Though considerable data exists on using nuclear SSRs to infer phylogenetic relationships, the potential of chloroplast microsatellites (cpSSR), in this regard, remains largely unexplored. In the present study we probe various nucleotide repeat motifs (NRMs) / types of SSRs present in chloroplast genomes (cpDNA) of 12 species belonging to Brassicaceae family. NRMs show a non-random distribution in coding and non-coding compartments of cpDNA. As expected, trinucleotide repeats are more common in coding regions while other repeat motifs are prominent in non-coding DNA. Total numbers of SSRs in coding region show little variation between species while considerable variation is exhibited by SSRs in non-coding regions. Finally, we have designed universal primers that yield polymorphic amplicons from all 12 species. Our analysis also suggests that amplicon length polymorphism shows no significant relationship with sequence based phylogeny of SSRs in cpDNA of Brassicaceae family.