National Maize Improvement Centre of China, China Agricultural University, Beijing 100193, China.
College of Agronomy, Synergetic Innovation Center of Henan Grain Crops and National Key Laboratory of Wheat and Maize Crop Science, Henan Agricultural University, Zhengzhou 450002, China.
Mol Plant. 2017 Mar 6;10(3):483-497. doi: 10.1016/j.molp.2017.02.002. Epub 2017 Feb 12.
Sugarcane mosaic virus (SCMV) causes substantial losses of grain yield and forage biomass in susceptible maize worldwide. A major quantitative trait locus, Scmv1, has been identified to impart strong resistance to SCMV at the early infection stage. Here, we demonstrate that ZmTrxh, encoding an atypical h-type thioredoxin, is the causal gene at Scmv1, and that its transcript abundance correlated strongly with maize resistance to SCMV. ZmTrxh alleles, whether they are resistant or susceptible, share the identical coding/proximal promoter regions, but vary in the upstream regulatory regions. ZmTrxh lacks two canonical cysteines in the thioredoxin active-site motif and exists uniquely in the maize genome. Because of this, ZmTrxh is unable to reduce disulfide bridges but possesses a strong molecular chaperone-like activity. ZmTrxh is dispersed in maize cytoplasm to suppress SCMV viral RNA accumulation. Moreover, ZmTrxh-mediated maize resistance to SCMV showed no obvious correlation with the salicylic acid- and jasmonic acid-related defense signaling pathways. Taken together, our results indicate that ZmTrxh exhibits a distinct defense profile in maize resistance to SCMV, differing from previously characterized dominant or recessive potyvirus resistance genes.
甘蔗花叶病毒（SCMV）会导致全球易感玉米的大量粮食产量和饲料生物量损失。一个主要的数量性状位点 Scmv1 已被确定为在早期感染阶段赋予对 SCMV 的强烈抗性。在这里，我们证明编码非典型 h 型硫氧还蛋白的 ZmTrxh 是 Scmv1 的致病基因，其转录丰度与玉米对 SCMV 的抗性密切相关。ZmTrxh 等位基因，无论其是否具有抗性，都具有相同的编码/近端启动子区域，但在上游调控区域存在差异。ZmTrxh 在硫氧还蛋白活性位点模体中缺少两个典型的半胱氨酸，并且在玉米基因组中独一无二。正因为如此，ZmTrxh 无法还原二硫键，但具有很强的分子伴侣样活性。ZmTrxh 分散在玉米细胞质中，抑制 SCMV 病毒 RNA 的积累。此外，ZmTrxh 介导的玉米对 SCMV 的抗性与水杨酸和茉莉酸相关的防御信号通路没有明显的相关性。总之，我们的结果表明，ZmTrxh 在玉米对 SCMV 的抗性中表现出独特的防御特征，与先前表征的显性或隐性马铃薯 Y 病毒抗性基因不同。
