Amino acid transport via phloem is one of the major source‐to‐sink nitrogen translocation pathways in most plant species. Amino acid permeases (AAPs) play essential roles in amino acid transport between plant cells and subsequent phloem or seed loading. In this study, a soybean AAP gene, annotated as GmAAP6a , was cloned and demonstrated to be significantly induced by nitrogen starvation. Histochemical staining of GmAAP6a:GmAAP6a‐GUS transgenic soybean revealed that GmAAP6a is predominantly expressed in phloem and xylem parenchyma cells. Growth and transport studies using toxic amino acid analogs or single amino acids as a sole nitrogen source suggest that GmAAP6a can selectively absorb and transport neutral and acidic amino acids. Overexpression of GmAAP6a in Arabidopsis and soybean resulted in elevated tolerance to nitrogen limitation. Furthermore, the source‐to‐sink transfer of amino acids in the transgenic soybean was markedly improved under low nitrogen conditions. At the vegetative stage, GmAAP6a‐overexpressing soybean showed significantly increased nitrogen export from source cotyledons and simultaneously enhanced nitrogen import into sink primary leaves. At the reproductive stage, nitrogen import into seeds was greatly enhanced under both sufficient and limited nitrogen conditions. Collectively, our results imply that overexpression of GmAAP6a enhances nitrogen stress tolerance and source‐to‐sink transport and improves seed quality in soybean. Co‐expression of GmAAP6a with genes specialized in source nitrogen recycling and seed loading may represent an interesting application potential in breeding.

中文翻译：

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GmAAP6a 的过表达可通过优化大豆中的氨基酸分配来增强对低氮的耐受性并改善种子氮状况。


通过韧皮部的氨基酸运输是大多数植物物种中主要的源-库氮易位途径之一。氨基酸渗透酶 (AAP) 在植物细胞之间的氨基酸转运以及随后的韧皮部或种子装载中发挥着重要作用。在这项研究中，克隆了大豆AAP基因（注释为GmAAP6a ） ，并证明该基因可通过氮饥饿显着诱导。 GmAAP6a:GmAAP6a-GUS转基因大豆的组织化学染色表明，GmAAP6a 主要在韧皮部和木质部薄壁细胞中表达。使用有毒氨基酸类似物或单一氨基酸作为唯一氮源的生长和运输研究表明，GmAAP6a 可以选择性吸收和运输中性和酸性氨基酸。 GmAAP6a在拟南芥和大豆中的过度表达导致对氮限制的耐受性升高。此外，转基因大豆的氨基酸从源到库的转移在低氮条件下得到了显着改善。在营养阶段， GmAAP6a过度表达的大豆显示出源子叶的氮输出显着增加，同时库初生叶的氮输入也增加。在繁殖阶段，在充足和有限的氮条件下，种子中的氮输入大大增加。总的来说，我们的结果表明， GmAAP6a的过度表达增强了大豆的氮胁迫耐受性和从源到库的运输，并提高了种子质量。 GmAAP6a与专门负责源氮循环和种子装载的基因的共表达可能代表了育种中有趣的应用潜力。