United States Department of Agriculture-Agricultural Research Service, Robert W. Holley Center for Agriculture and Health, Ithaca, New York 14853, USA.
G3 (Bethesda). 2013 Aug 7;3(8):1287-99. doi: 10.1534/g3.113.006148.
Tocopherols and tocotrienols, collectively known as tocochromanols, are the major lipid-soluble antioxidants in maize (Zea mays L.) grain. Given that individual tocochromanols differ in their degree of vitamin E activity, variation for tocochromanol composition and content in grain from among diverse maize inbred lines has important nutritional and health implications for enhancing the vitamin E and antioxidant contents of maize-derived foods through plant breeding. Toward this end, we conducted a genome-wide association study of six tocochromanol compounds and 14 of their sums, ratios, and proportions with a 281 maize inbred association panel that was genotyped for 591,822 SNP markers. In addition to providing further insight into the association between ZmVTE4 (γ-tocopherol methyltransferase) haplotypes and α-tocopherol content, we also detected a novel association between ZmVTE1 (tocopherol cyclase) and tocotrienol composition. In a pathway-level analysis, we assessed the genetic contribution of 60 a priori candidate genes encoding the core tocochromanol pathway (VTE genes) and reactions for pathways supplying the isoprenoid tail and aromatic head group of tocochromanols. This analysis identified two additional genes, ZmHGGT1 (homogentisate geranylgeranyltransferase) and one prephenate dehydratase parolog (of four in the genome) that also modestly contribute to tocotrienol variation in the panel. Collectively, our results provide the most favorable ZmVTE4 haplotype and suggest three new gene targets for increasing vitamin E and antioxidant levels through marker-assisted selection.
生育酚和三烯生育酚统称为生育三烯醇，是玉米（Zea mays L.）谷物中主要的脂溶性抗氧化剂。鉴于个体生育三烯醇在维生素 E 活性方面存在差异，不同玉米自交系的生育三烯醇组成和含量的差异对通过植物育种提高玉米衍生食品中的维生素 E 和抗氧化剂含量具有重要的营养和健康意义。为此，我们利用一个包含 281 个玉米自交系的关联面板，对 6 种生育三烯醇化合物及其 14 种总和、比率和比例进行了全基因组关联研究，该关联面板对 591,822 个 SNP 标记进行了基因分型。除了进一步深入了解 ZmVTE4（γ-生育酚甲基转移酶）单倍型与α-生育酚含量之间的关联外，我们还检测到 ZmVTE1（生育酚环化酶）与生育三烯醇组成之间的一个新关联。在途径水平分析中，我们评估了编码生育三烯醇核心途径（VTE 基因）和为生育三烯醇异戊烯基尾部和芳香头部基团提供途径的 60 个先验候选基因的遗传贡献。该分析确定了另外两个基因，ZmHGGT1（homogentisate geranylgeranyltransferase）和一个预苯酸脱水酶旁系同源物（基因组中有四个），它们也能适度影响该群体中生育三烯醇的变异。总的来说，我们的研究结果提供了最有利的 ZmVTE4 单倍型，并为通过标记辅助选择增加维生素 E 和抗氧化剂水平提出了三个新的基因目标。
