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Structural and functional comparative mapping between the Brassica A genomes in allotetraploid Brassica napus and diploid Brassica rapa

Jiang, Congcong, Ramchiary, Nirala, Ma, Yongbiao, Jin, Mina, Feng, Ji, Li, Ruiyuan, Wang, Hao, Long, Yan, Choi, Su Ryun, Zhang, Chunyu, Cowling, Wallace A., Park, Beom Seok, Lim, Yong Pyo, Meng, Jinling
Theoretical and applied genetics 2011 v.123 no.6 pp. 927-941
Brassica napus, Brassica rapa, bacterial artificial chromosomes, chromosome translocation, diploidy, genome, nucleotide sequences, oilseed crops, quantitative trait loci, seed quality
Brassica napus (AACC genome) is an important oilseed crop that was formed by the fusion of the diploids B. rapa (AA) and B. oleracea (CC). The complete genomic sequence of the Brassica A genome will be available soon from the B. rapa genome sequencing project, but it is not clear how informative the A genome sequence in B. rapa (Ar) will be for predicting the structure and function of the A subgenome in the allotetraploid Brassica species B. napus (An). In this paper, we report the results of structural and functional comparative mapping between the A subgenomes of B. napus and B. rapa based on genetic maps that were anchored with bacterial artificial chromosomes (BACs)-sequence of B. rapa. We identified segmental conservation that represented by syntenic blocks in over one third of the A genome; meanwhile, comparative mapping of quantitative trait loci for seed quality traits identified a dozen homologous regions with conserved function in the A genome of the two species. However, several genomic rearrangement events, such as inversions, intra- and inter-chromosomal translocations, were also observed, covering totally at least 5% of the A genome, between allotetraploid B. napus and diploid B. rapa. Based on these results, the A genomes of B. rapa and B. napus are mostly functionally conserved, but caution will be necessary in applying the full sequence data from B. rapa to the B. napus as a result of genomic rearrangements in the A genome between the two species.