The Lotus japonicus Sen1 gene controls rhizobial differentiation into nitrogen-fixing bacteroids in nodules
The Lotus japonicus Sen1 gene controls rhizobial differentiation into nitrogen-fixing bacteroids in nodules
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百脉根Sen1基因控制根瘤菌分化为固氮类菌
DOI：
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发表时间：
2003
期刊：
影响因子：
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通讯作者：
M. Kawaguchi
中科院分区：
文献类型：
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作者：
N. Suganuma;Y. Nakamura;M. Yamamoto;T. Ohta;H. Koiwa;S. Akao;M. Kawaguchi
本文对形成无效共生根瘤的日本莲子突变体Ljsym75进行了详细的特征鉴定，并确定了一个参与固氮过程的新位点。Ljsym75根瘤在植株发育的任何阶段均未检测到固氮活性，植株生长明显迟缓。Ljsym75植株形成的根瘤数量是野生型岐阜的两倍，而且这种表型不受低浓度硝酸盐施用的影响。虽然在Ljsym75上形成的无效结节在解剖结构上与有效岐阜结节相似，但Ljsym75结节过早衰老。镜检显示，被Ljsym75结节内吞的细菌未能分化为类细菌。此外，细菌不含氮酶蛋白，而在结节的细胞质中检测到豆红蛋白。这些结果表明，Ljsym75是结核中细菌向固氮类细菌分化所必需的，因此Ljsym75基因被重新命名为sen1（固定性内共生结核）。DNA标记连锁分析表明，Sen1位于第4染色体上。
A Lotus japonicus mutant, Ljsym75, which forms ineffective symbiotic nodules and defines a new locus involved in the process of nitrogen fixation, was characterized in detail in order to identify the stage of developmental arrest of the nodules. No nitrogen-fixing activity was detectable in Ljsym75 nodules at any stage during plant development, and plant growth was markedly retarded. Ljsym75 plants formed twice as many nodules as the wild-type Gifu, and this phenotype was not influenced by the application of low concentrations of nitrate. Although the ineffective nodules formed on Ljsym75 were anatomically similar to effective Gifu nodules, Ljsym75 nodules senesced prematurely. Microscopic examination revealed that bacteria endocytosed into Ljsym75 nodules failed to differentiate into bacteroids. Moreover, the bacteria contained no nitrogenase proteins, whereas leghemoglobin was detected in the cytosol of the nodules. These results indicate that Ljsym75 is required for bacterial differentiation into nitrogen-fixing bacteroids in nodules, and thus the Ljsym75 gene was renamed sen1 (for stationary endosymbiont nodule). Linkage analysis using DNA markers showed that Sen1 is located on chromosome 4.