Trading amino acids at the aphid-Buchnera symbiotic interface
Trading amino acids at the aphid-Buchnera symbiotic interface
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DOI：
10.1073/pnas.1906223116
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发表时间：
2019-08-06
影响因子：
11.1
通讯作者：
Thwaites, David T.
中科院分区：
文献类型：
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作者：
Feng, Honglin;Edwards, Noel;Thwaites, David T.
以植物汁液为食的昆虫分布广泛，尽管它们只以缺乏必需氨基酸和维生素的贫乏饮食为食，但它们已经进化到占据不同的环境生态位。成功很大程度上取决于它们与特殊真核细菌细胞内微生物共生体的共生关系。每个细菌细胞都充满了共生体，这些共生体分别被宿主衍生的共生体膜包围，代表了绝对的宿主-共生体界面。共生体膜必须是一种动态且选择性渗透的结构，以实现必需营养素、代谢物和生物合成中间体的双向和差异性运动，这对于宿主和共生体的生长和生存至关重要。然而，尽管具有这一至关重要的作用，但在所有含菌细胞的昆虫中，跨共生体膜的膜运输的分子基础仍未得到解决。转运蛋白免疫定位于共生体膜，将豌豆蚜 Acyrthosiphon pisum 与其胞内共生体 Buchnera aphidicola 分开。转运蛋白 A. pisum 非必需氨基酸转运蛋白 1 或 ApNEAAT1（基因：ACYPI008971）在爪蟾卵母细胞中异源表达后进行了功能表征，并介导小偶极氨基酸（丝氨酸、脯氨酸、半胱氨酸、丙氨酸、甘氨酸）的向内和向外转运。电中性 ApNEAAT1 转运由氨基酸浓度梯度驱动，不与跨膜离子梯度耦合。先前对血淋巴和细菌细胞的代谢物分析，以及宿主和共生体中的代谢途径分析，使得能够预测ApNEAAT1在双向宿主-共生体氨基酸转移中的生理作用，为宿主和共生体提供必需的营养物质和生物合成前体，以促进代谢互补。
Plant sap-feeding insects are widespread, having evolved to occupy diverse environmental niches despite exclusive feeding on an impoverished diet lacking in essential amino acids and vitamins. Success depends exquisitely on their symbiotic relationships with microbial symbionts housed within specialized eukaryotic bacteriocyte cells. Each bacteriocyte is packed with symbionts that are individually surrounded by a host-derived symbiosomal membrane representing the absolute host-symbiont interface. The symbiosomal membrane must be a dynamic and selectively permeable structure to enable bidirectional and differential movement of essential nutrients, metabolites, and biosynthetic intermediates, vital for growth and survival of host and symbiont. However, despite this crucial role, the molecular basis of membrane transport across the symbiosomal membrane remains unresolved in all bacteriocyte-containing insects. A transport protein was immuno-localized to the symbiosomal membrane separating the pea aphid Acyrthosiphon pisum from its intracellular symbiont Buchnera aphidicola. The transporter, A. pisum nonessential amino acid transporter 1, or ApNEAAT1 (gene: ACYPI008971), was characterized functionally following heterologous expression in Xenopus oocytes, and mediates both inward and outward transport of small dipolar amino acids (serine, proline, cysteine, alanine, glycine). Electroneutral ApNEAAT1 transport is driven by amino acid concentration gradients and is not coupled to transmembrane ion gradients. Previous metabolite profiling of hemolymph and bacteriocyte, alongside metabolic pathway analysis in host and symbiont, enable prediction of a physiological role for ApNEAAT1 in bidirectional host-symbiont amino acid transfer, supplying both host and symbiont with indispensable nutrients and biosynthetic precursors to facilitate metabolic complementarity.