Department of Evolutionary and Environmental Biology, Institute of Evolution, Faculty of Natural Sciences, University of Haifa, Mt. Carmel, Haifa, 31905, Israel.
Theor Appl Genet. 2011 Jan;122(1):175-87. doi: 10.1007/s00122-010-1434-2. Epub 2010 Sep 22.
Recombination is a key evolutionary factor enhancing diversity. However, the effect of recombination on diversity in inbreeding species is expected to be low. To estimate this effect, recombination and diversity patterns of Lr10 gene were studied in natural populations of the inbreeder species, wild emmer wheat (Triticum dicoccoides). Wild emmer wheat is the progenitor of most cultivated wheats and it harbors rich genetic resources for disease resistance. Lr10 is a leaf rust resistance gene encoding three domains: a coiled-coil, nucleotide-binding site, and leucine-rich repeat (CC-NBS-LRR).
Lr10 was sequenced from 58 accessions representing 12 diverse habitats in Israel. Diversity analysis revealed a high rate of synonymous and non-synonymous substitutions (d (S) = 0.029, d (N) = 0.018, respectively) in the NBS-LRR domains. Moreover, in contrast to other resistance genes, in Lr10 the CC domain was more diverse than the NBS-LRR domains (d (S) = 0.069 vs. 0.029, d (N) = 0.094 vs. 0.018) and was subjected to positive selection in some of the populations. Seventeen recombination events were detected between haplotypes, especially in the CC domain. Linkage disequilibrium (LD) analysis has shown a rapid decay from r (2) = 0.5 to r (2) = 0.1 within a 2-kb span.
These results suggest that recombination is a diversifying force for the R-gene, Lr10, in the selfing species T. dicoccoides. This is the first report of a short-range LD decay in wild emmer wheat.
重组是增强多样性的关键进化因素。然而，在自交物种中，重组对多样性的影响预计较低。为了估计这种影响，研究了自交物种野生二粒小麦（Triticum dicoccoides）自然种群中 Lr10 基因的重组和多样性模式。野生二粒小麦是大多数栽培小麦的祖先，它拥有丰富的抗病遗传资源。Lr10 是一个叶锈病抗性基因，编码三个结构域：一个卷曲螺旋结构域、核苷酸结合位点和富含亮氨酸重复序列（CC-NBS-LRR）。
从代表以色列 12 个不同生境的 58 个个体中对 Lr10 进行了测序。多样性分析显示，在 NBS-LRR 结构域中存在很高的同义突变和非同义突变率（d（S）=0.029，d（N）=0.018）。此外，与其他抗性基因不同，在 Lr10 中，CC 结构域比 NBS-LRR 结构域更具多样性（d（S）=0.069 对 0.029，d（N）=0.094 对 0.018），并且在一些群体中受到正选择。在单倍型之间检测到 17 个重组事件，特别是在 CC 结构域。连锁不平衡（LD）分析表明，在 2-kb 跨度内，r（2）从 0.5 迅速衰减到 0.1。
这些结果表明，重组是自交物种 T. dicoccoides 中 R 基因 Lr10 的一种多样化力量。这是首次报道在野生二粒小麦中存在短程 LD 衰减。
