The Signal Peptide of the Medicago truncatula Modular Nodulin MtNOD25 Operates as an Address Label for the Specific Targeting of Proteins to Nitrogen-Fixing Symbiosomes
The Signal Peptide of the Medicago truncatula Modular Nodulin MtNOD25 Operates as an Address Label for the Specific Targeting of Proteins to Nitrogen-Fixing Symbiosomes
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DOI：
10.1094/mpmi-22-1-0063
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发表时间：
2009-01-01
影响因子：
3.5
通讯作者：
Kuester, Helge
中科院分区：
文献类型：
--
作者：
Hohnjec, Natalija;Lenz, Frauke;Kuester, Helge
模式豆科植物蒺藜苜蓿（Medicago truncatula）的根瘤特异性MtNOD 25基因编码由不同的重复模块组成的模块化植物蛋白，所述重复模块两侧具有不同的N-和C-末端。虽然相似性低，相对于所有的重复模块，无论是N-末端信号肽（SP）和C-末端是高度保守的模块结球蛋白从不同的豆类。在细胞水平上，MtNOD 25仅在根瘤的感染细胞中转录，并且这种激活由含有器官特异性元件的299-bp最小启动子介导。通过在转基因结节中表达mGFP 6翻译融合体，我们表明MtNOD 25蛋白专门易位到受感染细胞的共生体。这种特异性靶向仅需要在豆类特异性共生体蛋白家族中高度保守的N-末端MtNOD 25 SP。我们的发现揭示了一种可能的机制，用于将宿主蛋白质递送到受感染的根瘤细胞的共生体中，此外，定义了一个仅24个氨基酸的短分子地址标签，其N-末端的存在足以使蛋白质跨类菌体膜易位。
The nodule-specific MtNOD25 gene of the model legume Medicago truncatula encodes a modular nodulin composed of different repetitive modules flanked by distinct N- and C-termini. Although similarities are low with respect to all repetitive modules, both the N-terminal signal peptide (SP) and the C-terminus are highly conserved in modular nodulins from different legumes. On the cellular level, MtNOD25 is only transcribed in the infected cells of root nodules, and this activation is mediated by a 299-bp minimal promoter containing an organ-specific element. By expressing mGFP6 translational fusions in transgenic nodules, we show that MtNOD25 proteins are exclusively translocated to the symbiosomes of infected cells. This specific targeting only requires an N-terminal MtNOD25 SP that is highly conserved across a family of legume-specific symbiosome proteins. Our finding sheds light on one possible mechanism for the delivery of host proteins to the symbiosomes of infected root nodule cells and, in addition, defines a short molecular address label of only 24 amino acids whose N-terminal presence is sufficient to translocate proteins across the peribacteroid membrane.