Alnus peptides modify membrane porosity and induce the release of nitrogen-rich metabolites from nitrogen-fixing Frankia
Alnus peptides modify membrane porosity and induce the release of nitrogen-rich metabolites from nitrogen-fixing Frankia
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DOI：
10.1038/ismej.2014.257
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发表时间：
2015-08-01
期刊：
影响因子：
11
通讯作者：
Normand, Philippe
中科院分区：
文献类型：
--
作者：
Carro, Lorena;Pujic, Petar;Normand, Philippe
放线根植物在先锋生态系统中的生长依赖于与固氮放线菌法兰克细胞的共生，这些细胞被安置在称为根瘤的特殊根器官中。固氮发生在被称为囊泡的分化的Frankia细胞中。在谷氨酰胺阶段之后，囊泡缺乏吸收氨的途径，并且应该将减少的氮转移到植物宿主细胞。然而，固氮产物向植物细胞转移的机制仍不清楚。在这里，描述了这种代谢交换的新元素。我们发现Alnus glutinosa结节表达防御素样肽，其中一个Ag5被发现靶向Frankia囊泡。体外和体内分析表明，Ag5诱导Frankia剧烈的生理变化，包括囊泡膜通透性增加。在Ag5处理的固氮培养中，含氮代谢物（主要是谷氨酰胺和谷氨酸）的释放显著。这项研究表明，Ag5肽在根瘤中的Frankia生理学中起着核心作用，并揭示了这一广泛存在的防御蛋白家族的一种新的细胞功能。
Actinorhizal plant growth in pioneer ecosystems depends on the symbiosis with the nitrogen-fixing actinobacterium Frankia cells that are housed in special root organs called nodules. Nitrogen fixation occurs in differentiated Frankia cells known as vesicles. Vesicles lack a pathway for assimilating ammonia beyond the glutamine stage and are supposed to transfer reduced nitrogen to the plant host cells. However, a mechanism for the transfer of nitrogen-fixation products to the plant cells remains elusive. Here, new elements for this metabolic exchange are described. We show that Alnus glutinosa nodules express defensin-like peptides, and one of these, Ag5, was found to target Frankia vesicles. In vitro and in vivo analyses showed that Ag5 induces drastic physiological changes in Frankia, including an increased permeability of vesicle membranes. A significant release of nitrogen-containing metabolites, mainly glutamine and glutamate, was found in N-2-fixing cultures treated with Ag5. This work demonstrates that the Ag5 peptide is central for Frankia physiology in nodules and uncovers a novel cellular function for this large and widespread defensin peptide family.