Cavell A C, Lydiate D J, Parkin I A, Dean C, Trick M
Department of Brassica and Oilseeds Research, John Innes Centre, Norwich Research Park, Colney, U.K.
Genome. 1998 Feb;41(1):62-9.
Arabidopsis thaliana (the model dicotyledonous plant) is closely related to Brassica crop species. Genome collinearity, or conservation of marker order, between Brassica napus (oilseed rape) and A. thaliana was assessed over a 7.5-Mbp region of the long arm of A. thaliana chromosome 4, equivalent to 30 cM. Estimates of copy number indicated that sequences present in a single copy in the haploid genome of A. thaliana (n = 5) were present in 2-8 copies in the haploid genome of B. napus (n = 19), while sequences present in multiple copies in A. thaliana were present in over 10 copies in B. napus. Genetic mapping in B. napus of DNA markers derived from a segment of A. thaliana chromosome 4 revealed duplicated homologous segments in the B. napus genome. Physical mapping in A. thaliana of homologues of Brassica clones derived from these regions confirmed the identity of six duplicated segments with substantial homology to the 7.5-Mbp region of chromosome 4 in A. thaliana. These six duplicated Brassica regions (on average 22 cM in length) are collinear, except that two of the six copies contain the same large internal inversion. These results have encouraging implications for the feasibility of shuttling between the physical map of A. thaliana and genetic maps of Brassica species, for identifying candidate genes and for map based gene cloning in Brassica crops.
拟南芥（模式双子叶植物）与芸苔属作物物种亲缘关系密切。在拟南芥4号染色体长臂的一个750万碱基对区域（相当于30厘摩）内，评估了甘蓝型油菜（油菜籽）与拟南芥之间的基因组共线性，即标记顺序的保守性。拷贝数估计表明，拟南芥单倍体基因组（n = 5）中以单拷贝形式存在的序列，在甘蓝型油菜单倍体基因组（n = 19）中以2 - 8个拷贝形式存在，而拟南芥中以多拷贝形式存在的序列，在甘蓝型油菜中以超过10个拷贝形式存在。对源自拟南芥4号染色体一段的DNA标记在甘蓝型油菜中的遗传定位揭示了甘蓝型油菜基因组中存在重复的同源片段。对源自这些区域的芸苔属克隆的同源物在拟南芥中的物理定位，证实了六个重复片段与拟南芥4号染色体750万碱基对区域具有高度同源性。这六个重复的芸苔属区域（平均长度为22厘摩）是共线的，只是六个拷贝中的两个包含相同的大的内部倒位。这些结果对于在拟南芥物理图谱和芸苔属物种遗传图谱之间穿梭、鉴定候选基因以及芸苔属作物基于图谱的基因克隆的可行性具有令人鼓舞的意义。
