病害是影響作物高產穩(wěn)產的重要因素之一,。植物抗病基因 (Plant disease resistance gene，簡稱R基因)在長期的進化過程中表現(xiàn)出復雜的進化模式,。很多研究表明,，植物R基因是以基因家族的形式存在，通常成簇排列從而形成復雜結構。經由旁系同源抗病基因間頻繁的序列重組和交換的一類抗性基因叫I型R基因,，而較少或沒有經過旁系同源基因序列重組和交換的基因為II型R基因,。
中國科學院植物種質創(chuàng)新與特色農業(yè)重點實驗室、武漢植物園植物應用基因組學學科組首席科學家彭俊華研究員與華中農業(yè)大學長江學者匡漢暉教授開展合作研究,，通過分析21個禾本科物種R基因RP1的序列,，揭示其進化模式及在長期進化過程中的分化機理。
該研究發(fā)現(xiàn),，RP1基因在禾本科物種中存在著復雜的復制,、刪除等遺傳事件，在不同的物種中存在不同的拷貝數(shù),，其祖先物種中僅存在2個RP1位點,，在現(xiàn)有物種中卻存在1-5個拷貝。在長期進化過程中因旁系同源基因的重組和交換造成了玉米和小麥基因組中存在多個RP1同源基因,。頻繁的序列交換和重組并沒有導致玉米屬不同物種間RP1基因的協(xié)同進化,，卻在玉米和高粱屬間存在協(xié)同進化的現(xiàn)象。I型和II型R基因很可能在水稻祖先種中已經分化,。水稻大部分抗病功能基因家族與其旁系同源基因間存在頻繁的序列交換,，其中Pi37由2個相鄰的旁系同源基因不對稱交換造成了4個點突變。
該研究為R基因克隆,、作用機理及植物R基因工程育種奠定了基礎,。相關研究論文Contrasting Evolutionary Patterns of the Rp1 Resistance Gene Family in Different Species of Poaceae近期發(fā)表于國際期刊《分子生物學與進化》 Mol. Biol. Evol. （(2011) 28 (1): 313-325）。（生物谷Bioon.com）
生物谷推薦原文出處：
Mol Biol Evol (2011) 28 (1): 313-325. doi: 10.1093/molbev/msq216
Contrasting Evolutionary Patterns of the Rp1 Resistance Gene Family in Different Species of Poaceae
Sha Luo,1, Junhua Peng?,2, Kunpeng Li1, Min Wang1 and Hanhui Kuang*,1
Abstract
Disease-resistance genes (R-genes) in plants show complex evolutionary patterns. We investigated the evolution of the Rp1 R-gene family in Poaceae, and 409 Rp1 fragments were sequenced from 21 species. Our data showed that the common ancestor of Poaceae had two Rp1 loci, but the number of Rp1 locus in extant species varies from one to five. Some wheat and Zea genotypes have dozens of Rp1 homologues in striking contrast to one or two copies in Brachypodium distachyon. The large number of diverse Rp1 homologues in Zea was the result of duplications followed by extensive sequence exchanges among paralogues, and all genes in maize have evolved in a pattern of Type I R-genes. The high frequency of sequence exchanges did not cause concerted evolution in Zea species, but concerted evolution was obvious between Rp1 homologues from genera Zea and Sorghum. Differentiation of Type I and Type II Rp1 homologues was observed in Oryza species, likely occurred in their common ancestor. One member (Type II R-gene) in the Oryza Rp1 cluster did not change sequences with its paralogues, whereas the other paralogues (Type I R-genes) had frequent sequence exchanges. The functional Pi37 resistance gene in rice was generated through an unequal crossover between two neighboring paralogues followed by four point mutations. The Rp1 homologues in wheat and barley were most divergent, probably due to lack of sequence exchanges among them. Our results shed more light on R-gene evolution, particularly on the differentiation of Type I and Type II R-genes.
