Formation of organelle-like N2-fixing symbiosomes in legume root nodules is controlled by DMI2
Formation of organelle-like N2-fixing symbiosomes in legume root nodules is controlled by DMI2
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DOI：
10.1073/pnas.0504284102
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发表时间：
2005-07-19
影响因子：
11.1
通讯作者：
Geurts, R
中科院分区：
文献类型：
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作者：
Limpens, E;Mirabella, R;Geurts, R
在大多数豆科植物根瘤中，固氮根瘤菌在其宿主细胞内以细胞器样结构存在。这些结构，称为共生体，包含一个或几个根瘤菌被植物膜包围。共生体的形成需要细菌从细胞壁结合的感染线中释放出来。在原始豆科植物中，根瘤菌是在细胞内感染线，而不是共生体，是由细胞壁。共生体的形成被认为是豆科植物-根瘤共生进化的一个重要步骤，因为共生体促进了两个共生体之间的代谢物交换。在这里，我们表明，基因，这是必不可少的启动结节形成，也积极转录在成熟的蒺藜苜蓿结节的共生体形成发生的区域。这些基因中至少有一个编码受体激酶2（DM 12），对共生体的形成至关重要。该蛋白定位于宿主细胞质膜和感染丝周围的膜。DM 12表达的部分减少导致类似于在原始豆科植物结节中发现的感染结构的表型，因为被感染的细胞被大的细胞内感染线而不是被细胞器样共生体占据。
In most legume nodules, the N-2-fixing rhizobia are present as organelle-like structures inside their host cells. These structures, named symbiosomes, contain one or a few rhizobia surrounded by a plant membrane. Symbiosome formation requires the release of bacteria from cell-wall-bound infection threads. In primitive legumes, rhizobia are hosted in intracellular infection threads that, in contrast to symbiosomes, are bound by a cell wall. The formation of symbiosomes is presumed to represent a major step in the evolution of legume-nodule symbiosis, because symbiosomes facilitate the exchange of metabolites between the two symbionts. Here, we show that the genes, which are essential for initiating nodule formation, are also actively transcribed in mature Medicago truncatula nodules in the region where symbiosome formation occurs. At least one of these genes, encoding the receptor kinase DOES NOT MAKE INFECTIONS 2 (DM12) is essential for symbiosome formation. The protein locates to the host cell plasma membrane and to the membrane surrounding the infection threads. A partial reduction of DM12 expression causes a phenotype that resembles the infection structures found in primitive legume nodules, because infected cells are occupied by large intracellular infection threads instead of by organelle-like symbiosomes.