Multiple Avirulence Loci and Allele-Specific Effector Recognition Control the Pm3 Race-Specific Resistance of Wheat to Powdery Mildew
Multiple Avirulence Loci and Allele-Specific Effector Recognition Control the Pm3 Race-Specific Resistance of Wheat to Powdery Mildew
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DOI：
10.1105/tpc.15.00171
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发表时间：
2015-10-01
期刊：
影响因子：
11.6
通讯作者：
Keller, Beat
中科院分区：
文献类型：
--
作者：
Bourras, Salim;McNally, Kaitlin Elyse;Keller, Beat
在谷物中，一些抗霉基因以大的等位基因序列出现；例如，在小麦（Triticum aestivum和Triticum turgidum）中，17个功能性Pm3等位基因赋予了对白粉病（Blumeria graminis）具有重要农艺意义的种族特异性抗性。小麦品种特异性的分子基础已被确定，但对白粉病相应的无毒基因知之甚少。在这里，我们分析了6个Pm3等位基因的毒力遗传，发现三个主要的Avr位点影响毒力，其中一个共同的位点_1参与了所有AvrPm3-Pm3的相互作用。我们从locus_2中克隆出被Pm3a和Pm3f等位基因识别的效应基因AvrPm3（a2/f2）。在烟叶和小麦的瞬时测定中诱导Pm3等位基因依赖的超敏反应显示出特异性。基因表达分析显示，bg1（由locus_1编码）和AvrPm3（a2/f2）在分离株间存在显著差异，表明除蛋白多态性外，表达水平对毒力也有影响。我们提出了一个涉及三个组成部分的小种特异性模型：等位基因特异性毒性效应，抗性基因等位基因和病原体编码的毒性抑制因子。因此，虽然一个遗传上简单的等位基因系列控制着植物寄主的特异性，但对病原体一侧的识别更为复杂，允许灵活的进化反应和对抗性基因的适应。
In cereals, several mildew resistance genes occur as large allelic series; for example, in wheat (Triticum aestivum and Triticum turgidum), 17 functional Pm3 alleles confer agronomically important race-specific resistance to powdery mildew (Blumeria graminis). The molecular basis of race specificity has been characterized in wheat, but little is known about the corresponding avirulence genes in powdery mildew. Here, we dissected the genetics of avirulence for six Pm3 alleles and found that three major Avr loci affect avirulence, with a common locus_1 involved in all AvrPm3-Pm3 interactions. We cloned the effector gene AvrPm3(a2/f2) from locus_2, which is recognized by the Pm3a and Pm3f alleles. Induction of a Pm3 allele-dependent hypersensitive response in transient assays in Nicotiana benthamiana and in wheat demonstrated specificity. Gene expression analysis of Bcg1 (encoded by locus_1) and AvrPm3(a2/f2) revealed significant differences between isolates, indicating that in addition to protein polymorphisms, expression levels play a role in avirulence. We propose a model for race specificity involving three components: an allele-specific avirulence effector, a resistance gene allele, and a pathogen-encoded suppressor of avirulence. Thus, whereas a genetically simple allelic series controls specificity in the plant host, recognition on the pathogen side is more complex, allowing flexible evolutionary responses and adaptation to resistance genes.