病害是影响作物高产稳产的重要因素之一。植物抗病基因 (Plant disease resistance gene，简称R基因)在长期的进化过程中表现出复杂的进化模式。很多研究表明，植物R基因是以基因家族的形式存在，通常成簇排列从而形成复杂结构。经由旁系同源抗病基因间频繁的序列重组和交换的一类抗性基因叫I型R基因，而较少或没有经过旁系同源基因序列重组和交换的基因为II型R基因。
中国科学院植物种质创新与特色农业重点实验室、武汉植物园植物应用基因组学学科组首席科学家彭俊华研究员与华中农业大学长江学者匡汉晖教授开展合作研究，通过分析21个禾本科物种R基因RP1的序列，揭示其进化模式及在长期进化过程中的分化机理。
该研究发现，RP1基因在禾本科物种中存在着复杂的复制、删除等遗传事件，在不同的物种中存在不同的拷贝数，其祖先物种中仅存在2个RP1位点，在现有物种中却存在1-5个拷贝。在长期进化过程中因旁系同源基因的重组和交换造成了玉米和小麦基因组中存在多个RP1同源基因。频繁的序列交换和重组并没有导致玉米属不同物种间RP1基因的协同进化，却在玉米和高粱属间存在协同进化的现象。I型和II型R基因很可能在水稻祖先种中已经分化。水稻大部分抗病功能基因家族与其旁系同源基因间存在频繁的序列交换，其中Pi37由2个相邻的旁系同源基因不对称交换造成了4个点突变。
该研究为R基因克隆、作用机理及植物R基因工程育种奠定了基础。相关研究论文Contrasting Evolutionary Patterns of the Rp1 Resistance Gene Family in Different Species of Poaceae近期发表于国际期刊《分子生物学与进化》 Mol. Biol. Evol. （(2011) 28 (1): 313-325）。（生物谷Bioon.com）
生物谷推荐原文出处：
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.
