The Eight Amino-Acid Differences Within Three Leucine-Rich Repeats Between Pi2 and Piz-t Resistance Proteins Determine the Resistance Specificity to Magnaporthe grisea

Bo Zhou, Shaohong Qu, Guifu Liu, Maureen Dolan, Hajime Sakai, Guodong Lu, Maria Bellizzi, Guo-Liang Wang
Molecular Plant-Microbe Interactions, 2006, 19(11): 1216-1228  DOI: 10.1094/MPMI-19-1216     追溯原文......本站官方QQ群:62473826

The rice blast resistance (R) genes Pi2 and Piz-t confer broad-spectrum resistance against different sets of Magnaporthe grisea isolates. We first identified the Pi2 gene using a map-based cloning strategy. The Pi2 gene is a member of a gene cluster comprising nine gene members (named Nbs1-Pi2 to Nbs9-Pi2) and encodes a protein with a nucleotide-binding site and leucine-rich repeat (LRR) domain. Fine genetic mapping, molecular characterization of the Pi2 susceptible mutants, and complementation tests indicated that Nbs4-Pi2 is the Pi2 gene. The Piz-t gene, a Pi2 allele in the rice cultivar Toride 1, was isolated based on the Pi2 sequence information. Complementation tests confirmed that the family member Nbs4-Piz-t is Piz-t. Sequence comparison revealed that only eight amino-acid changes, which are confined within three consecutive LRR, differentiate Piz-t from Pi2. Of the eight variants, only one locates within the xxLxLxx motif. A reciprocal exchange of the single amino acid between Pi2 and Piz-t did not convert the resistance specificity to each other but, rather, abolished the function of both resistance proteins. These results indicate that the single amino acid in the xxLxLxx motif may be critical for maintaining the recognition surface of Pi2 and Piz-t to their respective avirulence proteins.

Pi2和Piz-t抗病蛋白在3个富亮氨酸重复区间上8个不同的氨基酸决定了两者对稻瘟病菌存在抗性差异

稻瘟病广谱抗性基因(R)Pi2Piz-t对多套稻瘟病菌株具有抗性。我们采用图位克隆的方法确定了Pi2基因,它是一个含9个成员基因簇(分别命名为Nbs1-Pi2Nbs9-Pi2)的一个,编码一个含有核苷酸结合位点和富亮氨酸重复序列(LRR)结构域的蛋白质。通过精细定位,Pi2感病突变体的分子鉴定和互补实验表明,Nbs4-Pi2Pi2基因。Piz-t是水稻品种Toride 1中Pi2的等位基因,根据Pi2的序列信息分离出来。互补试验证明该家族成员的Nbs4-Piz-tPiz-t。序列比对显示Pi2与Piz-t在三个连续的LRR区间存在8个氨基酸的不同差异,8个突变氨基酸只有一个位于xxLxLxx结构内。在Pi2和Piz-t间互换这个突变氨基酸并不会交换两者的抗性特征,而是使这两个抗性蛋白失去功能。这些结果表明这个在xxLxLxx结构内的氨基酸是Pi2和Piz-t抗性蛋白表面结构的关键,从而识别对应的无毒蛋白。


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