Institute of Plant Science and Resources, Okayama University, Chuo 2-20-1, Kurashiki 710-0046, Japan.
Advanced Science Research Center, Okayama University, Okayama 700-8530, Japan.
Nature. 2017 Jan 5;541(7635):92-95. doi: 10.1038/nature20610. Epub 2016 Dec 21.
Phosphorus is an important nutrient for crop productivity. More than 60% of the total phosphorus in cereal crops is finally allocated into the grains and is therefore removed at harvest. This removal accounts for 85% of the phosphorus fertilizers applied to the field each year. However, because humans and non-ruminants such as poultry, swine and fish cannot digest phytate, the major form of phosphorus in the grains, the excreted phosphorus causes eutrophication of waterways. A reduction in phosphorus accumulation in the grain would contribute to sustainable and environmentally friendly agriculture. Here we describe a rice transporter, SULTR-like phosphorus distribution transporter (SPDT), that controls the allocation of phosphorus to the grain. SPDT is expressed in the xylem region of both enlarged- and diffuse-vascular bundles of the nodes, and encodes a plasma-membrane-localized transporter for phosphorus. Knockout of this gene in rice (Oryza sativa) altered the distribution of phosphorus, with decreased phosphorus in the grains but increased levels in the leaves. Total phosphorus and phytate in the brown de-husked rice were 20-30% lower in the knockout lines, whereas yield, seed germination and seedling vigour were not affected. These results indicate that SPDT functions in the rice node as a switch to allocate phosphorus preferentially to the grains. This finding provides a potential strategy to reduce the removal of phosphorus from the field and lower the risk of eutrophication of waterways.
磷是作物生产力的重要营养物质。谷物中超过 60%的总磷最终被分配到籽粒中，因此在收获时被去除。这一去除量占每年施用于田间的磷肥的 85%。然而，由于人类和非反刍动物（如家禽、猪和鱼）无法消化谷物中磷的主要形式植酸，因此排出的磷会导致水道富营养化。减少谷物中磷的积累将有助于可持续和环境友好型农业。在这里，我们描述了一种控制磷向籽粒分配的水稻转运蛋白，SULTR 样磷分布转运蛋白（SPDT）。SPDT 在节点的扩大维管束和扩散维管束的木质部区域表达，并编码一种用于磷的质膜定位转运蛋白。敲除水稻（Oryza sativa）中的该基因改变了磷的分布，使籽粒中的磷减少，但叶片中的磷增加。敲除系中糙米的总磷和植酸含量降低了 20-30%，而产量、种子发芽率和幼苗活力不受影响。这些结果表明，SPDT 在水稻节点中作为一种开关，优先将磷分配到籽粒中。这一发现为减少从田间去除磷和降低水道富营养化的风险提供了一种潜在策略。
