Department of Plant and Soil Sciences, University of Delaware, Newark, DE 19716-1304, USA.
Proc Natl Acad Sci U S A. 2011 May 3;108(18):7339-44. doi: 10.1073/pnas.1011739108. Epub 2011 Apr 13.
Plants are attacked by pathogens representing diverse taxonomic groups, such that genes providing multiple disease resistance (MDR) are expected to be under positive selection pressure. To address the hypothesis that naturally occurring allelic variation conditions MDR, we extended the framework of structured association mapping to allow for the analysis of correlated complex traits and the identification of pleiotropic genes. The multivariate analytical approach used here is directly applicable to any species and set of traits exhibiting correlation. From our analysis of a diverse panel of maize inbred lines, we discovered high positive genetic correlations between resistances to three globally threatening fungal diseases. The maize panel studied exhibits rapidly decaying linkage disequilibrium that generally occurs within 1 or 2 kb, which is less than the average length of a maize gene. The positive correlations therefore suggested that functional allelic variation at specific genes for MDR exists in maize. Using a multivariate test statistic, a glutathione S-transferase (GST) gene was found to be associated with modest levels of resistance to all three diseases. Resequencing analysis pinpointed the association to a histidine (basic amino acid) for aspartic acid (acidic amino acid) substitution in the encoded protein domain that defines GST substrate specificity and biochemical activity. The known functions of GSTs suggested that variability in detoxification pathways underlie natural variation in maize MDR.
植物受到代表不同分类群的病原体的攻击，因此预计提供多种疾病抗性（MDR）的基因将受到正选择压力。为了解释自然发生的等位基因变异条件 MDR 的假设，我们扩展了结构关联映射的框架，以允许分析相关的复杂性状和鉴定多效基因。这里使用的多变量分析方法可直接应用于任何表现出相关性的物种和性状集。从对玉米自交系的多样化面板的分析中，我们发现了三种全球威胁性真菌病抗性之间的高度正遗传相关性。所研究的玉米面板表现出迅速衰减的连锁不平衡，通常发生在 1 或 2 kb 内，这小于玉米基因的平均长度。因此，正相关性表明玉米中存在特定 MDR 基因的功能等位基因变异。使用多变量检验统计量，发现谷胱甘肽 S-转移酶（GST）基因与三种疾病的中度抗性有关。重测序分析将关联定位到编码蛋白结构域中组氨酸（碱性氨基酸）到天冬氨酸（酸性氨基酸）的取代，该取代定义了 GST 底物特异性和生化活性。GST 的已知功能表明，解毒途径的变异性是玉米 MDR 中自然变异的基础。
