Sweigard J A, Carroll A M, Kang S, Farrall L, Chumley F G, Valent B
DuPont Central Research and Development, E. I. du Pont de Nemours and Company, Wilmington, Delaware 19880-0402, USA.
Plant Cell. 1995 Aug;7(8):1221-33. doi: 10.1105/tpc.7.8.1221.
Genetic analysis of host specificity in the rice blast fungus (Magnaporthe grisea) identified a single gene, PWL2 (for Pathogenicity toward Weeping Lovegrass), that exerts a major effect on the ability of this fungus to infect weeping lovegrass (Eragrostis curvula). The allele of the PWL2 gene conferring nonpathogenicity was genetically unstable, with the frequent appearance of spontaneous pathogenic mutants. PWL2 was cloned based on its map position. Large deletions detected in pathogenic mutants guided the gene cloning efforts. Transformants harboring the cloned PWL2 gene lost pathogenicity toward weeping lovegrass but remained fully pathogenic toward other host plants. Thus, the PWL2 host species specificity gene has properties analogous to classical avirulence genes, which function to prevent infection of certain cultivars of a particular host species. The PWL2 gene encodes a glycine-rich, hydrophilic protein (16 kD) with a putative secretion signal sequence. The pathogenic allele segregating in the mapping population, pwl2-2, differed from PWL2 by a single base pair substitution that resulted in a loss of function. The PWL2 locus is highly polymorphic among rice pathogens from diverse geographic locations.
对稻瘟病菌（稻瘟病疫霉）寄主特异性的遗传分析鉴定出一个单一基因，即PWL2（对垂穗画眉草的致病性），该基因对这种真菌感染垂穗画眉草（弯叶画眉草）的能力具有主要影响。赋予无致病性的PWL2基因等位基因在遗传上不稳定，经常出现自发的致病突变体。根据其图谱位置克隆了PWL2。在致病突变体中检测到的大片段缺失指导了基因克隆工作。携带克隆的PWL2基因的转化体对垂穗画眉草失去致病性，但对其他寄主植物仍保持完全致病性。因此，PWL2寄主物种特异性基因具有与经典无毒基因类似的特性，其功能是防止感染特定寄主物种的某些品种。PWL2基因编码一种富含甘氨酸的亲水性蛋白质（16kD），带有一个假定的分泌信号序列。在作图群体中分离的致病等位基因pwl2 - 2与PWL2的区别在于一个单碱基对替换，导致功能丧失。PWL2基因座在来自不同地理位置的水稻病原体中高度多态。
