AUTHOR=Zheng Jin-shuang , Sun Cheng-zhen , Zhang Shu-ning , Hou Xi-lin , Bonnema Guusje 

TITLE=Cytogenetic Diversity of Simple Sequences Repeats in Morphotypes of Brassica rapa ssp. chinensis

JOURNAL=Frontiers in Plant Science

VOLUME=7

YEAR=2016

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2016.01049

DOI=10.3389/fpls.2016.01049

ISSN=1664-462X

ABSTRACT=<p>A significant fraction of the nuclear DNA of all eukaryotes is comprised of simple sequence repeats (SSRs). Although these sequences are widely used for studying genetic variation, linkage mapping and evolution, little attention had been paid to the chromosomal distribution and cytogenetic diversity of these sequences. In this paper, we report the distribution characterization of mono-, di-, and tri-nucleotide SSRs in <italic>Brassica rapa</italic> ssp. <italic>chinensis</italic>. Fluorescence <italic>in situ</italic> hybridization was used to characterize the cytogenetic diversity of SSRs among morphotypes of <italic>B. rapa</italic> ssp. <italic>chinensis</italic>. The proportion of different SSR motifs varied among morphotypes of <italic>B. rapa</italic> ssp. <italic>chinensis</italic>, with tri-nucleotide SSRs being more prevalent in the genome of <italic>B. rapa</italic> ssp. <italic>chinensis</italic>. We determined the chromosomal locations of mono-, di-, and tri-nucleotide repeat loci. The results showed that the chromosomal distribution of SSRs in the different morphotypes is non-random and motif-dependent, and allowed us to characterize the relative variability in terms of SSR numbers and similar chromosomal distributions in centromeric/peri-centromeric heterochromatin. The differences between SSR repeats with respect to abundance and distribution indicate that SSRs are a driving force in the genomic evolution of <italic>B. rapa</italic> species. Our results provide a comprehensive view of the SSR sequence distribution and evolution for comparison among morphotypes <italic>B. rapa</italic> ssp. <italic>chinensis</italic>.</p>