Frary A, Presting G G, Tanksley S D
Department of Plant Breeding and Biometry, Cornell University, Ithaca NY 14853, USA.
Mol Gen Genet. 1996 Feb 25;250(3):295-304. doi: 10.1007/BF02174387.
The centromeres of two tomato chromosomes have been precisely localized on the molecular linkage map through dosage analysis of trisomic stocks. To map the centromeres of chromosomes 7 and 9, complementary telo-, secondary, and tertiary trisomic stocks were used to assign DNA markers to their respective chromosome arms and thus to localize the centromere at the junction of the short and long arms. It was found that both centromeres are situated within a cluster of cosegregating markers. In an attempt to order the markers within the centric clusters, genetic maps of the centromeric regions of chromosomes 7 and 9 were constructed from F2 populations of 1620 Lycopersicon esculentum x L. pennellii (E x P) plants and 1640 L. esculentum x L. pimpinellifolium (E x PM) plants. Despite the large number of plants analyzed, very few recombination events were detected in the centric regions, indicating a significant suppression of recombination at this region of the chromosome. The fact that recombination suppression is equally strong in crosses between closely related (E x PM) and remotely related (E x P) parents suggests that centromeric suppression is not due to DNA sequence mismatches but to some other mechanism. The greatest number of centromeric markers was resolved in the L. esculentum x L. pennellii F2 population. The centromere of chromosome 7 is surrounded by eight cosegregating markers: three on the short arm, five on the long arm. Similarly, the centric region of chromosome 9 contains ten cosegregating markers including one short arm marker and nine long arm markers. The localization of centromeres to precise intervals on the molecular linkage map represents the first step towards the characterization and ultimate isolation of tomato centromeres.
通过三体材料的剂量分析，已将两个番茄染色体的着丝粒精确地定位在分子连锁图谱上。为了定位7号和9号染色体的着丝粒，使用了互补的端体、次级和三级三体材料，将DNA标记分配到各自的染色体臂上，从而将着丝粒定位在短臂和长臂的交界处。结果发现，两个着丝粒都位于共分离标记的簇内。为了对着丝粒簇内的标记进行排序，从1620株番茄（Lycopersicon esculentum）×潘那利番茄（L. pennellii）（E×P）植株和1640株番茄×小番茄（L. pimpinellifolium）（E×PM）植株的F2群体构建了7号和9号染色体着丝粒区域的遗传图谱。尽管分析的植株数量很多，但在着丝粒区域检测到的重组事件很少，表明该染色体区域的重组受到显著抑制。在亲缘关系近的（E×PM）和远缘的（E×P）亲本之间的杂交中，重组抑制同样强烈，这一事实表明着丝粒抑制不是由于DNA序列错配，而是由于其他一些机制。在番茄×潘那利番茄的F2群体中解析出的着丝粒标记数量最多。7号染色体的着丝粒被8个共分离标记包围：短臂上有3个，长臂上有5个。同样，9号染色体的着丝粒区域包含10个共分离标记，包括1个短臂标记和9个长臂标记。将着丝粒定位到分子连锁图谱上的精确区间，是朝着番茄着丝粒的表征和最终分离迈出的第一步。
