Abstract：
Wheat (Triticum aestivum L.) is one of the most important crops worldwide and a major source of human Cd intake. Limiting grain Cd concentration (Gr_Cd_Conc) in wheat is necessary to ensure food safety. However, the genetic factors associated with Cd uptake, translocation, distribution, and Gr_Cd_Conc in wheat are poorly understood. Here, we mapped quantitative trait loci (QTL) for Gr_Cd_Conc and its related transport pathway using a recombinant inbred line (RIL_DT) population derived from two Polish wheat varieties (dwarf Polish wheat [DPW] and tall Polish wheat [TPW]). We identified 29 novel major QTLs for grain and tissue Cd concentration; 14 novel major QTLs for Cd uptake, translocation, and distribution; and 27 major QTLs for agronomic traits. We also analyzed the pleiotropy of these QTLs. Six novel QTLs (QGr_Cd_Conc-1A, QGr_Cd_Conc-3A, QGr_Cd_Conc-4B, QGr_Cd_Conc-5B, QGr_Cd_Conc-6A and QGr_Cd_Conc-7A) for Gr_Cd_Conc explained 8.16-17.02% of the phenotypic variation. QGr_Cd_Conc-3A, QGr_Cd_Conc-6A and QGr_Cd_Conc-7A pleiotropically regulated Cd transport; three other QTLs were organ-specific for Gr_Cd_Conc. We fine-mapped the locus of QGr_Cd_Conc-4B and identified the candidate gene as Cation/Ca exchanger 2 (TpCCX2-4B), which was differentially expressed in DPW and TPW. It encodes an endoplasmic reticulum membrane/plasma membrane-localized Cd efflux transporter in yeast. Overexpression of TpCCX2-4B reduced Gr_Cd_Conc in rice. The average Gr_Cd_Conc was significantly lower in TpCCX2-4BDPW genotypes than in TpCCX2-4BTPWgenotypes of the RIL_DT population and two other natural populations, based on a KASP marker derived from the different promoter sequences between TpCCX2-4BDPW and TpCCX2-4BTPW. Our study reveals the genetic mechanism of Cd accumulation in wheat and provides valuable resources for genetic improvement of low-Cd-accumulating wheat cultivars.
摘要：
小麦（TriticumaestivumL.）是世界上最重要的作物之一，也是人类Cd摄入量的主要来源。限制小麦籽粒Cd浓度(Gr_Cd_Conc)是保证粮食安全的必要条件。然而,与Cd吸收相关的遗传因素，易位,分布，对小麦中的Gr_Cd_Conc和Gr_Cd_Conc了解甚少。这里,我们使用来自两个波兰小麦品种（矮波兰小麦[DPW]和高波兰小麦[TPW]）的重组自交系（RIL_DT）种群，对Gr_Cd_Conc及其相关运输途径进行了定位。我们确定了29个新的主要QTL用于谷物和组织Cd浓度;14个新的主要QTL用于Cd吸收，易位,和分布；以及27个主要农艺性状的QTL。我们还分析了这些QTL的多效性。六个新的QTL(QGr_Cd_Conc-1A，QGr_Cd_Conc-3A,QGr_Cd_Conc-4B,QGr_Cd_Conc-5B,Gr_Cd_Conc的QGr_Cd_Conc-6A和QGr_Cd_Conc-7A）解释了8.16-17.02％的表型变异。QGr_Cd_Conc-3A,QGr_Cd_Conc-6A和QGr_Cd_Conc-7A多向调节Cd运输；另外三个QTL对Gr_Cd_Conc具有器官特异性。我们对QGr_Cd_Conc-4B的基因座进行了精细定位，并将候选基因鉴定为阳离子/Ca交换体2（TpCCX2-4B），在DPW和TPW中差异表达。它在酵母中编码内质网膜/质膜定位的Cd外排转运蛋白。TpCCX2-4B的过表达降低了水稻中的Gr_Cd_Conc。TpCCX2-4BDPW基因型的平均Gr_Cd_Conc明显低于RIL_DT种群和其他两个自然种群的TpCCX2-4BTPW基因型,基于源自TpCCX2-4BDPW和TpCCX2-4BTPW之间的不同启动子序列的KASP标记。我们的研究揭示了小麦Cd积累的遗传机制，为低Cd积累小麦品种的遗传改良提供了宝贵的资源。
