Genomic structure and evolution of the Pi2/9 locus in wild rice species

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Liangying Dai, Jun Wu, Xunbo Li, Xuejun Wang, Xionglun Liu, Chatchawan Jantasuriyarat, Dave Kudrna, Yeisoo Yu, Rod A. Wing, Bin Han, Bo Zhou, Guo-Liang Wang
Theoretical and Applied Genetics, 2010, 121(2): 295-309  DOI: 10.1007/s00122-010-1310-0     追溯原文......本站官方QQ群:62473826

Rice blast, caused by the fungal pathogen Magnaporthe oryzae, is a devastating disease of rice worldwide. Among the 85 mapped resistance (R) genes against blast, 13 have been cloned and characterized. However, how these genes originated and how they evolved in the Oryza genus remains unclear. We previously cloned the rice blast R-genes Pi2, Pi9, and Piz-t, and analyzed their genomic structure and evolution in cultivated rice. In this study, we determined the genomic sequences of the Pi2/9 locus in four wild Oryza species representing three genomes (AA, BB and CC). The number of Pi2/9 family members in the four wild species ranges from two copies to 12 copies. Although these genes are conserved in structure and categorized into the same subfamily, sequence duplications and subsequent inversions or uneven crossing overs were observed, suggesting that the locus in different wild species has undergone dynamic changes. Positive selection was found in the leucine-rich repeat region of most members, especially in the largest clade where Pi9 is included. We also provide evidence that the Pi9 gene is more related to its homologues in the recurrent line and other rice cultivars than to those in its alleged donor species O. minuta, indicating a possible origin of the Pi9 gene from O. sativa. Comparative sequence analysis between the four wild Oryza species and the previously established reference sequences in cultivated rice species at the Pi2/9 locus has provided extensive and unique information on the genomic structure and evolution of a complex R-gene cluster in the Oryza genus.

野生稻中Pi2/9位点的基因组结构和进化

稻瘟病是由真菌稻瘟病菌引发的全球破坏性水稻疾病。在已定位85个抗性基因(R)中, 13个被克隆和鉴定。然而对于这些基因的起源以及在水稻中是如何进化的仍不明确。我们之前克隆了稻瘟病R基因Pi2Pi9Piz-t,并分析了它们在栽培稻中的基因结构和进化。在本项研究中,我们确定了代表3种基因组(AA、BB和CC)的4个野生稻种中Pi2/9位点的基因组序列。在4个野生种中Pi2/9家族成员数量范围从2个拷贝到12个拷贝。尽管这些基因结构保守并且属于同一个亚家族,但是出现的序列重复和反转或不均匀的跨越表明不同的野生种中该基因位点已发生了动态变化。大多数成员的富含亮氨酸重复区域存在正向选择,特别是在包含了Pi9的最大分支上。我们还证明在回归系及其他水稻品种中Pi9与其同系物的相关性要比其供体物种小粒野生稻中同系物的亲缘性更近,这表明Pi9可能起源自栽培稻。通过比对分析Pi2/9基因座在四个野生稻品种和先前多个栽培稻品种中的序列,为研究稻瘟病抗性基因簇的基因结构和进化提供了广泛独特的信息。


基因列表
  稻瘟病抗性基因 Pi9; Pi2/Piz-5; Pi50; Piz; Pi