Department of Plant Physiology and Bayreuth Center of Ecology and Environmental Research, University of Bayreuth, Universitätsstrasse 30, 95447, Bayreuth, Germany.
Plant Cell Environ. 2019 Oct;42(10):2902-2912. doi: 10.1111/pce.13627. Epub 2019 Aug 13.
Acquisition and homeostasis of micronutrients such as iron (Fe) and zinc (Zn) pose specific challenges. Poor solubility and high reactivity require controlled synthesis and supply of ligands to complex these metals extracellularly and intracellularly. Cytosolic labile pools represent only a minute fraction of the total cellular content. Several low-molecular-weight ligands are known in plants, including sulfur ligands (cysteine and peptides), nitrogen/oxygen ligands (S-adenosyl-l-methionine-derived molecules and histidine), and oxygen ligands (phenolics and organic acids). Some ligands are secreted into the extracellular space and influence the phytoavailability of metal ions. A second principal function is the intracellular buffering of micronutrients as well as the facilitation of long-distance transport in xylem and phloem. Furthermore, low-molecular-weight ligands are involved in the storage of metals, predominantly in vacuoles. A detailed molecular understanding is hampered by technical limitations, in particular the difficulty to detect and quantify cellular metal-ligand complexes. More, but still too little, is known about ligand synthesis and the transport across membranes, either with or without a complexed metal. Metal ligands have an immediate impact on human well-being. Engineering metal ligand synthesis and distribution in crops has tremendous potential to improve the nutritional quality of food and to tackle major human health risks.
获取和维持微量营养素（如铁（Fe）和锌（Zn））具有特殊的挑战性。较差的溶解性和高反应性要求控制合成和供应配体，以在细胞外和细胞内络合这些金属。细胞质的可溶池仅代表总细胞含量的一小部分。植物中已知有几种低分子量配体，包括硫配体（半胱氨酸和肽）、氮/氧配体（S-腺苷甲硫氨酸衍生的分子和组氨酸）和氧配体（酚类和有机酸）。一些配体分泌到细胞外空间，影响金属离子的植物可利用性。第二个主要功能是作为细胞内的微量元素缓冲剂，并促进木质部和韧皮部的长距离运输。此外，低分子量配体还参与金属的储存，主要在液泡中。由于技术限制，特别是难以检测和定量细胞内金属-配体复合物，对其详细的分子理解受到阻碍。关于配体的合成以及与或不与络合金属的跨膜运输，我们虽然了解更多，但仍然知之甚少。金属配体对人类健康有直接影响。在作物中工程化金属配体的合成和分布具有极大的潜力，可以提高食物的营养价值，并解决主要的人类健康风险。
