State Key Laboratory of Crop Genetics and Germplasm Enhancement, MOA Key Laboratory of Plant Nutrition and Fertilization in Lower-Middle Reaches of the Yangtze River, Nanjing Agricultural University, Nanjing, 210095, China.
School of Biological Sciences, Washington State University, Pullman, WA, 99164, USA.
Plant J. 2020 Jul;103(1):395-411. doi: 10.1111/tpj.14742. Epub 2020 Apr 28.
In agricultural soils, amino acids can represent vital nitrogen (N) sources for crop growth and yield. However, the molecular mechanisms underlying amino acid uptake and allocation are poorly understood in crop plants. This study shows that rice (Oryza sativa L.) roots can acquire aspartate at soil concentration, and that japonica subspecies take up this acidic amino acid 1.5-fold more efficiently than indica subspecies. Genetic association analyses with 68 representative japonica or indica germplasms identified rice Lysine-Histidine-type Transporter 1 (OsLHT1) as a candidate gene associated with the aspartate uptake trait. When expressed in yeast, OsLHT1 supported cell growth on a broad spectrum of amino acids, and effectively transported aspartate, asparagine and glutamate. OsLHT1 is localized throughout the rice root, including root hairs, epidermis, cortex and stele, and to the leaf vasculature. Knockout of OsLHT1 in japonica resulted in reduced root uptake of amino acids. Furthermore, in N-amino acid-fed mutants versus wild-type, a higher percentage of N remained in roots instead of being allocated to the shoot. N-ammonium uptake and subsequently the delivery of root-synthesized amino acids to Oslht1 shoots were also significantly decreased, which was accompanied by reduced shoot growth. These results together provide evidence that OsLHT1 functions in both root uptake and root to shoot allocation of a broad spectrum of amino acids in rice.
在农业土壤中，氨基酸可以作为作物生长和产量的重要氮（N）源。然而，作物中氨基酸吸收和分配的分子机制还知之甚少。本研究表明，水稻（Oryza sativa L.）根系可以在土壤浓度下吸收天冬氨酸，并且粳亚种比籼亚种更有效地吸收这种酸性氨基酸，吸收效率高 1.5 倍。对 68 个具有代表性的粳稻或籼稻种质资源进行遗传关联分析，鉴定出水稻赖氨酸-组氨酸型转运蛋白 1（OsLHT1）是与天冬氨酸吸收性状相关的候选基因。当在酵母中表达时，OsLHT1 支持细胞在广泛的氨基酸上生长，并有效地转运天冬氨酸、天冬酰胺和谷氨酸。OsLHT1 在整个水稻根系中都有表达，包括根毛、表皮、皮层和中柱，以及叶片脉管系统。粳稻 OsLHT1 的敲除导致氨基酸在根系中的吸收减少。此外，在 N-氨基酸喂养的突变体与野生型相比，更多的 N 留在根部而不是分配到地上部分。N-铵的吸收以及随后根合成的氨基酸向 Oslht1 地上部分的输送也显著减少，这伴随着地上部分生长的减少。这些结果共同证明 OsLHT1 在水稻中广泛吸收和向地上部分分配各种氨基酸方面都发挥作用。
