Nitrogen (N) is a major element necessary for crop yield. In most plants, organic N is primarily transported in the form of amino acids. Here, we show that amino acid permease 1 (AAP1) functions as a positive regulator of growth and grain yield in rice. We found that the OsAAP1 gene is highly expressed in rice axillary buds, leaves, and young panicles, and that the OsAAP1 protein is localized to both the plasma membrane and the nuclear membrane. Compared with the wild-type ZH11, OsAAP1 overexpression (OE) lines exhibited increased filled grain numbers as a result of enhanced tillering, while RNAi and CRISPR (clustered regularly interspaced short palindromic repeat; Osaap1) knockout lines showed the opposite phenotype. In addition, OsAAP1-OE lines had higher concentrations of neutral and acidic amino acids, but lower concentrations of basic amino acids in the straw. An exogenous treatment with neutral amino acids promoted axillary bud outgrowth more strongly in the OE lines than in the WT, RNAi, or Osaap1 lines. Transcriptome analysis of Osaap1 further demonstrated that OsAAP1 may affect N transport and metabolism, and auxin, cytokinin, and strigolactone signaling in regulating rice tillering. Taken together, these results support that increasing neutral amino acid uptake and reallocation via OsAAP1 could improve growth and grain yield in rice.

中文翻译：

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氨基酸转运蛋白AAP1通过调节水稻中性氨基酸的吸收和再分配来介导生长和谷物产量。

氮（N）是作物产量所必需的主要元素。在大多数植物中，有机氮主要以氨基酸形式运输。在这里，我们显示了氨基酸通透酶1（AAP1）作为水稻生长和籽粒产量的正向调节剂。我们发现，OsAAP1基因在水稻腋芽，叶和幼穗中高度表达，并且OsAAP1蛋白既定位在质膜上，又定位在核膜上。与野生型ZH11相比，OsAAP1过表达（OE）系显示出增加的分till，从而增加了实粒数，而RNAi和CRISPR（聚簇成规则间隔的短回文重复；Osaap1）敲除系显示出相反的表型。此外，OsAAP1-OE系的中性和酸性氨基酸浓度较高，而秸秆中的碱性氨基酸浓度较低。与WT，RNAi或Osaap1系相比，用中性氨基酸进行外源处理在OE系中更能促进腋芽的生长。Osaap1的转录组分析进一步表明，OsAAP1可能影响氮的转运和代谢，并在调节水稻分ing中影响生长素，细胞分裂素和松果内酯信号传导。综上所述，这些结果支持通过OsAAP1增加中性氨基酸的摄取和重新分配可以改善水稻的生长和籽粒产量。