Deciphering the Diploid Ancestral Genome of the Mesohexaploid Brassica rapa

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Authors	CHENG Feng MANDÁKOVÁ Terezie WU Jian XIE Qi LYSÁK Martin WANG Xiaowu
Year of publication	2013
Type	Article in Periodical
Magazine / Source	Plant Cell
MU Faculty or unit	Central European Institute of Technology
Citation
Web	http://www.plantcell.org/content/early/2013/05/06/tpc.113.110486.abstract
Doi	http://dx.doi.org/10.1105/tpc.113.110486
Field	Genetics and molecular biology
Keywords	CHROMOSOME-NUMBER REDUCTION; ARABIDOPSIS-THALIANA; SPECIES BRASSICACEAE; KARYOTYPE EVOLUTION; RAPHANUS-SATIVUS; SEQUENCE; PHYLOGENY; MAP; BLOCKS; RECONSTRUCTION
Description	The genus Brassica includes several important agricultural and horticultural crops. Their current genome structures were shaped by whole-genome triplication followed by extensive diploidization. The availability of several crucifer genome sequences, especially that of Chinese cabbage (Brassica rapa), enables study of the evolution of the mesohexaploid Brassica genomes from their diploid progenitors. We reconstructed three ancestral subgenomes of B. rapa (n = 10) by comparing its whole-genome sequence to ancestral and extant Brassicaceae genomes. All three B. rapa paleogenomes apparently consisted of seven chromosomes, similar to the ancestral translocation Proto-Calepineae Karyotype (tPCK; n = 7), which is the evolutionarily younger variant of the Proto-Calepineae Karyotype (n = 7). Based on comparative analysis of genome sequences or linkage maps of Brassica oleracea, Brassica nigra, radish (Raphanus sativus), and other closely related species, we propose a two-step merging of three tPCK-like genomes to form the hexaploid ancestor of the tribe Brassiceae with 42 chromosomes. Subsequent diversification of the Brassiceae was marked by extensive genome reshuffling and chromosome number reduction mediated by translocation events and followed by loss and/or inactivation of centromeres. Furthermore, via interspecies genome comparison, we refined intervals for seven of the genomic blocks of the Ancestral Crucifer Karyotype (n = 8), thus revising the key reference genome for evolutionary genomics of crucifers.
Related projects:	CEITEC - Central European Institute of Technology Evoluce a funkce komplexních genomů rostlin