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Logo of bmcgenoBioMed Centralsearchsubmit a manuscriptregisterthis articleBMC Genomics
BMC Genomics. 2009; 10: 432.
Published online Sep 15, 2009. doi:  10.1186/1471-2164-10-432
PMCID: PMC2761421
Sequenced BAC anchored reference genetic map that reconciles the ten individual chromosomes of Brassica rapa
HyeRan Kim,#1,6 Su Ryun Choi,#2 Jina Bae,2 Chang Pyo Hong,2 Seo Yeon Lee,2 Md Jamil Hossain,2 Dan Van Nguyen,2 Mina Jin,3 Beom-Seok Park,3 Jea-Wook Bang,4 Ian Bancroft,5 and Yong Pyo Limcorresponding author1,2
1Plant Genomics Institute, Chungnam National University, Daejeon, 305-764 Korea
2Department of Horticulture, Chungnam National University, Daejeon, 305-764 Korea
3National Institute of Agricultural Biotechnology, Rural Development Administration, Suwon, 441-707 Korea
4Department of Biology, Chungnam National University, Daejeon, 305-764 Korea
5Department of Crop Genetics, John Innes Centre, Norwich Research Park, Colney, Norwich NR4 7UH, UK
6Macrogen Inc., Seoul 153-023, Korea
corresponding authorCorresponding author.
#Contributed equally.
HyeRan Kim: hkim/at/; Su Ryun Choi: ssrchoi/at/; Jina Bae: akira2743/at/; Chang Pyo Hong: idhcp/at/; Seo Yeon Lee: phose84/at/; Md Jamil Hossain: mjamil_71/at/; Dan Van Nguyen: nvdan100/at/; Mina Jin: genemina/at/; Beom-Seok Park: pbeom/at/; Jea-Wook Bang: bangjw/at/; Ian Bancroft: ian.bancroft/at/; Yong Pyo Lim: yplim/at/
Received July 11, 2008; Accepted September 15, 2009.
In view of the immense value of Brassica rapa in the fields of agriculture and molecular biology, the multinational Brassica rapa Genome Sequencing Project (BrGSP) was launched in 2003 by five countries. The developing BrGSP has valuable resources for the community, including a reference genetic map and seed BAC sequences. Although the initial B. rapa linkage map served as a reference for the BrGSP, there was ambiguity in reconciling the linkage groups with the ten chromosomes of B. rapa. Consequently, the BrGSP assigned each of the linkage groups to the project members as chromosome substitutes for sequencing.
We identified simple sequence repeat (SSR) motifs in the B. rapa genome with the sequences of seed BACs used for the BrGSP. By testing 749 amplicons containing SSR motifs, we identified polymorphisms that enabled the anchoring of 188 BACs onto the B. rapa reference linkage map consisting of 719 loci in the 10 linkage groups with an average distance of 1.6 cM between adjacent loci. The anchored BAC sequences enabled the identification of 30 blocks of conserved synteny, totaling 534.9 cM in length, between the genomes of B. rapa and Arabidopsis thaliana. Most of these were consistent with previously reported duplication and rearrangement events that differentiate these genomes. However, we were able to identify the collinear regions for seven additional previously uncharacterized sections of the A genome. Integration of the linkage map with the B. rapa cytogenetic map was accomplished by FISH with probes representing 20 BAC clones, along with probes for rDNA and centromeric repeat sequences. This integration enabled unambiguous alignment and orientation of the maps representing the 10 B. rapa chromosomes.
We developed a second generation reference linkage map for B. rapa, which was aligned unambiguously to the B. rapa cytogenetic map. Furthermore, using our data, we confirmed and extended the comparative genome analysis between B. rapa and A. thaliana. This work will serve as a basis for integrating the genetic, physical, and chromosome maps of the BrGSP, as well as for studies on polyploidization, speciation, and genome duplication in the genus Brassica.
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