Beijing Key Laboratory of Growth and Developmental Regulation for Protected Vegetable Crops, College of Horticulture, China Agricultural University, Beijing, 100193, China.
New Phytol. 2023 Jul;239(2):639-659. doi: 10.1111/nph.18947. Epub 2023 May 2.
Amino acid transporters are the principal mediators of organic nitrogen distribution within plants and are essential for plant growth and development. Despite this importance, relatively few amino acid transporter genes have been explored and elucidated in cucumber (Cucumis sativus). Here, a total of 86 amino acid transporter genes were identified in the cucumber genome. We further identified Amino Acid Permease (AAP) subfamily members that exhibited distinct expression patterns in different tissues. We found that the CsAAP2 as a candidate gene encoding a functional amino acid transporter is highly expressed in cucumber root vascular cells. CsAAP2 knockout lines exhibited arrested development of root meristem, which then caused the delayed initiation of lateral root and the inhibition of root elongation. What is more, the shoot growth of aap2 mutants was strongly retarded due to defects in cucumber root development. Moreover, aap2 mutants exhibited higher concentrations of amino acids and lignin in roots. We found that the mutant roots had a stronger ability to acidize medium. Furthermore, in the aap2 mutants, polar auxin transport was disrupted in the root tip, leading to high auxin levels in roots. Interestingly, slightly alkaline media rescued their severely reduced root growth by stimulating auxin pathway.
氨基酸转运蛋白是植物体内有机氮分布的主要介质，对植物的生长和发育至关重要。尽管如此，在黄瓜（Cucumis sativus）中，相对较少的氨基酸转运蛋白基因被探索和阐明。在这里，在黄瓜基因组中总共鉴定出 86 个氨基酸转运蛋白基因。我们进一步鉴定了氨基酸渗透酶（AAP）亚家族成员，它们在不同组织中表现出不同的表达模式。我们发现，候选基因 CsAAP2 编码一个功能齐全的氨基酸转运蛋白，在黄瓜根血管细胞中高度表达。CsAAP2 敲除系表现出根分生组织发育停滞，随后导致侧根起始延迟和根伸长抑制。更重要的是，由于黄瓜根系发育缺陷，aap2 突变体的地上部生长受到强烈抑制。此外，aap2 突变体的根中氨基酸和木质素浓度更高。我们发现，突变体的根具有更强的酸化介质的能力。此外，在 aap2 突变体中，根尖端的极性生长素运输被破坏，导致根中生长素水平升高。有趣的是，略碱性的培养基通过刺激生长素途径挽救了其严重减少的根生长。
