Intragenic recombination and diversifying selection contribute to the evolution of downy mildew resistance at the RPP8 locus of arabidopsis
Intragenic recombination and diversifying selection contribute to the evolution of downy mildew resistance at the RPP8 locus of arabidopsis
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DOI：
10.1105/tpc.10.11.1861
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发表时间：
1998-11-01
期刊：
影响因子：
11.6
通讯作者：
Dangl, JL
中科院分区：
文献类型：
--
作者：
McDowell, JM;Dhandaydham, M;Dangl, JL
NBS-LRR类病原体抗性（R）基因（核苷酸结合位点和富含亮氨酸的重复序列）存在于许多植物物种中，并赋予对多种病原体的抗性。关于在宿主-病原体军备竞赛中驱动NBS-LRR基因进化的机制知之甚少。我们克隆了RPP 8基因（用于抗霜霉病），并比较了抗性兰茨贝格直立（Ler-0）和敏感哥伦比亚（Col-0）种质在该位点的等位基因结构。RPP 8-Ler编码具有推定的N-末端亮氨酸拉链的NBS-LRR蛋白，并且与先前克隆的赋予对细菌病原体的抗性的R基因比与其他已知的RPP基因更密切相关。Ler-0中的RPP 8单倍型包含功能性RPP 8-Ler基因和非功能性同源物RPH 8A。相反，Col-0中的rpp 8基因座包含单个嵌合基因，其可能源自Ler样单倍型内RPP 8-Ler和RPH 8A祖先之间的不等交换。RPP 8家族成员之间的序列差异已经通过对LRR中推定的配体结合区的正选择而加速。这些观察结果表明，NBS-LRR分子进化是由相同的机制驱动的，这些机制促进了参与非自我识别的其他基因之间的快速序列多样化。
Pathogen resistance (R) genes of the NBS-LRR class (for nucleotide binding site and leucine-rich repeat) are found in many plant species and confer resistance to a diverse spectrum of pathogens. Little is known about the mechanisms that drive NBS-LRR gene evolution in the host-pathogen arms race. We cloned the RPP8 gene (for resistance to Peronospora parasitica) and compared the structure of alleles at this locus in resistant Landsberg erecta (Ler-0) and susceptible Columbia (Col-0) accessions. RPP8-Ler encodes an NBS-LRR protein with a putative N-terminal leucine zipper and is more closely related to previously cloned R genes that confer resistance to bacterial pathogens than it is to other known RPP genes. The RPP8 haplotype in Ler-0 contains the functional RPP8-Ler gene and a nonfunctional homolog, RPH8A. In contrast, the rpp8 locus in Col-0 contains a single chimeric gene, which was likely derived from unequal crossing over between RPP8-Ler and RPH8A ancestors within a Ler-like haplotype. Sequence divergence among RPP8 family members has been accelerated by positive selection on the putative ligand binding region in the LRRs. These observations indicate that NBS-LRR molecular evolution is driven by the same mechanisms that promote rapid sequence diversification among other genes involved in non-self-recognition.