Centre for Membrane Pumps in Cells and Disease-PUMPKIN, Danish National Research Foundation, Denmark.
Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, DK-1871 Frederiksberg, Denmark.
Nat Plants. 2016 Apr 11;2(5):16036. doi: 10.1038/nplants.2016.36.
Insufficient intake of zinc and iron from a cereal-based diet is one of the causes of 'hidden hunger' (micronutrient deficiency), which affects some two billion people(1,2). Identifying a limiting factor in the molecular mechanism of zinc loading into seeds is an important step towards determining the genetic basis for variation of grain micronutrient content and developing breeding strategies to improve this trait(3). Nutrients are translocated to developing seeds at a rate that is regulated by transport processes in source leaves, in the phloem vascular pathway, and at seed sinks. Nutrients are released from a symplasmic maternal seed domain into the seed apoplasm surrounding the endosperm and embryo by poorly understood membrane transport processes(4-6). Plants are unique among eukaryotes in having specific P1B-ATPase pumps for the cellular export of zinc(7). In Arabidopsis, we show that two zinc transporting P1B-ATPases actively export zinc from the mother plant to the filial tissues. Mutant plants that lack both zinc pumps accumulate zinc in the seed coat and consequently have vastly reduced amounts of zinc inside the seed. Blockage of zinc transport was observed at both high and low external zinc supplies. The phenotype was determined by the mother plant and is thus due to a lack of zinc pump activity in the seed coat and not in the filial tissues. The finding that P1B-ATPases are one of the limiting factors controlling the amount of zinc inside a seed is an important step towards combating nutritional zinc deficiency worldwide.
从谷物为主的饮食中摄入的锌和铁不足是“隐性饥饿”（微量营养素缺乏）的原因之一，全球约有 20 亿人受到影响(1,2)。确定锌加载到种子的分子机制中的限制因素是确定谷物微量营养素含量变化的遗传基础和开发改善该特性的育种策略的重要步骤(3)。营养物质以受源叶中运输过程、韧皮部血管途径和种子汇调节的速率转运到发育中的种子。营养物质通过膜运输过程从母体种子域中的胞质体释放到围绕胚乳和胚的种子质外体(4-6)。植物在具有用于细胞输出锌的特定 P1B-ATPase 泵方面在真核生物中是独特的(7)。在拟南芥中，我们表明两种锌转运 P1B-ATPase 从母体植物主动将锌输出到子体组织。缺乏这两种锌泵的突变体植物在种皮中积累锌，因此种子内部的锌含量大大减少。在高锌和低锌供应下都观察到锌转运的阻断。该表型由母体植物决定，因此是由于种皮中的锌泵活性缺乏，而不是子体组织中的缺乏。发现 P1B-ATPase 是控制种子内部锌含量的限制因素之一，这是全球对抗营养性锌缺乏的重要一步。
