Lukaszewski A J, Rybka K, Korzun V, Malyshev S V, Lapinski B, Whitkus R
Department of Botany and Plant Sciences, University of California, Riverside, CA 92521, USA.
Genome. 2004 Feb;47(1):36-45. doi: 10.1139/g03-089.
Wide hybrids have been used in generating genetic maps of many plant species. In this study, genetic and physical mapping was performed on ph1b-induced recombinants of rye chromosome 2R in wheat (Triticum aestivum L.). All recombinants were single breakpoint translocations. Recombination 2RS-2BS was absent from the terminal and the pericentric regions and was distributed randomly along an intercalary segment covering approximately 65% of the arm's length. Such a distribution probably resulted from structural differences at the telomeres of 2RS and wheat 2BS arm that disrupted telomeric initiation of pairing. Recombination 2RL-2BL was confined to the terminal 25% of the arm's length. A genetic map of homoeologous recombination 2R-2B was generated using relative recombination frequencies and aligned with maps of chromosomes 2B and 2R based on homologous recombination. The alignment of the short arms showed a shift of homoeologous recombination toward the centromere. On the long arms, the distribution of homoeologous recombination was the same as that of homologous recombination in the distal halves of the maps, but the absence of multiple crossovers in homoeologous recombination eliminated the proximal half of the map. The results confirm that homoeologous recombination in wheat is based on single exchanges per arm, indicate that the distribution of these single homoeologous exchanges is similar to the distribution of the first (distal) crossovers in homologues, and suggest that successive crossovers in an arm generate specific portions of genetic maps. A difference in the distribution of recombination between the short and long arms indicates that the distal crossover localization in wheat is not dictated by a restricted distribution of DNA sequences capable of recombination but by the pattern of pairing initiation, and that can be affected by structural differences. Restriction of homoeologous recombination to single crossovers in the distal part of the genetic map complicates chromosome engineering efforts targeting genes in the proximal map regions.
远缘杂交已被用于构建许多植物物种的遗传图谱。在本研究中，对小麦（普通小麦）中ph1b诱导的黑麦2R染色体重组体进行了遗传和物理作图。所有重组体均为单断点易位。2RS - 2BS之间的重组在末端和着丝粒周围区域不存在，而是随机分布在一个覆盖约65%臂长的中间区段。这种分布可能是由于2RS和小麦2BS臂端粒的结构差异破坏了端粒配对起始。2RL - 2BL之间的重组局限于臂长的末端25%。利用相对重组频率构建了同源重组2R - 2B的遗传图谱，并与基于同源重组的2B和2R染色体图谱进行比对。短臂的比对显示同源重组向着丝粒方向偏移。在长臂上，同源重组的分布与图谱远端半部同源重组的分布相同，但同源重组中没有多个交叉互换，从而消除了图谱近端半部。结果证实小麦中的同源重组基于每条臂的单次交换，表明这些单次同源交换的分布与同源染色体中首次（远端）交叉互换的分布相似，并表明一条臂上连续的交叉互换产生了遗传图谱的特定部分。短臂和长臂之间重组分布的差异表明，小麦中远端交叉互换的定位不是由能够重组的DNA序列的受限分布决定的，而是由配对起始模式决定的，并且可能受到结构差异的影响。将同源重组限制在遗传图谱远端部分的单交叉互换会使针对图谱近端区域基因的染色体工程工作变得复杂。
