具有广谱抗性的单一位点对作物育种家们来说是价值连城的资源，小麦中的Lr67、Lr34和水稻中的GH3-2都具有类似的特征。最近，美国科学家在玉米中也发现了同样的广谱抗性位点。
qMdr9.02是玉米中鉴定的位于第9染色体上的数量性状位点。该位点对三个真菌类病害灰斑病、南方叶枯病、北方叶枯病有很好的防治效果。研究人员通过精细定位、关联分析、表达分析、插入诱变、转基因验证等一系列技术手段证实，qMdr9.02位点对抗病性起作用的基因是 ZmCCoAOMT2（GRMZM2G099363）。该基因编码咖啡酰辅酶A-O-甲基转移酶，该酶参与类苯基丙烷和脂氧合酶代谢途径，对木质素的合成有重要作用。ZmCCoAOMT2通过强化植物细胞壁，抑制植物细胞编程性死亡来实现抗病的效果。该基因氨基酸序列的差异导致了表达水平的多样性，最终造成了该位点在玉米品种中抗病性状的遗传多态性。ZmCCoAOMT2基因的发现和功能验证对于培育广谱抗病玉米品种、理解作物对真菌病的抗性机理都意义重大。
Nature Genetics, 24 July 2017
A gene encoding maize caffeoyl-CoA O-methyltransferase confers quantitative resistance to multiple pathogens
Author
Qin Yang, Yijian He, Mercy Kabahuma……Xu Li, Nick Lauter & Peter Balint-Kurti*
*: Department of Entomology and Plant Pathology, North Carolina State University; USDA-ARS Plant Science Research Unit, USA.
Abstract
Alleles that confer multiple disease resistance (MDR) are valuable in crop improvement, although the molecular mechanisms underlying their functions remain largely unknown. A quantitative trait locus, qMdr9.02, associated with resistance to three important foliar maize diseases—southern leaf blight, gray leaf spot and northern leaf blight—has been identified on maize chromosome 9. Through fine-mapping, association analysis, expression analysis, insertional mutagenesis and transgenic validation, we demonstrate that ZmCCoAOMT2, which encodes a caffeoyl-CoA O-methyltransferase associated with the phenylpropanoid pathway and lignin production, is the gene within qMdr9.02 conferring quantitative resistance to both southern leaf blight and gray leaf spot. We suggest that resistance might be caused by allelic variation at the level of both gene expression and amino acid sequence, thus resulting in differences in levels of lignin and other metabolites of the phenylpropanoid pathway and regulation of programmed cell death.
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