Genetic and physical analysis of the nodD3 region of Rhizobium meliloti.
Genetic and physical analysis of the nodD3 region of Rhizobium meliloti.
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苜蓿根瘤菌 nodD3 区域的遗传和物理分析。
DOI：
10.1093/nar/19.4.921
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发表时间：
1991
影响因子：
14.9
通讯作者：
Long,SR
中科院分区：
文献类型：
--
作者：
Rushing,BG;Yelton,MM;Long,SR
苜蓿根瘤菌（Rhizobium meliloti）的结瘤基因（nod）是由nod基因家族中的蛋白激活因子调控的。虽然NodD 1和NodD 2与宿主豆科植物提供的小分子量诱导剂协同作用，但NodD 3是nod启动子的诱导剂非依赖性激活剂。我们测定了nodD 3基因的序列，证实了一个35 kDa的蛋白在体外的表达，并确定了5个Tn 5插入片段在nodD 3基因区域的插入点。我们发现NodD 3的氨基酸序列显着偏离NodD 1和NodD 2的序列，这是更相似的诱导剂依赖的NodD的另一个物种，根瘤菌豆类生物变种viciae。目前还不能很好地理解NodD 3的表达，但至少涉及SyrM，另一种与LysR-NodD家族相关的阳性激活剂。在NodD 3节点调节的遗传研究中使用的表型突变Tn插入之一缺乏NodD 3蛋白，如通过蛋白质印迹所确定的，但另一个表达约50-60%的野生型水平。这些Tn 5插入的位置基本上在NodD 3的开放阅读框的上游，表明相对较远的调节序列对NodD 3表达的重要性。不引起NodD 3-表型的插入位于蛋白质编码区的最末端C-末端。
The nodulation (nod) genes of the symbiont Rhizobium meliloti are transcriptionally controlled by protein activators in thenodDgene family. While NodD1 and NodD2 act in concert with small molecular weight inducers provided by the host legume plant, NodD3 is an inducer-independent activator of the nod promoters. We determined the sequence of thenodD3gene, confirmed the expression of a 35 kDa proteinin vitro, and determined the insertion points of five Tn5 insertions in the region of thenodD3gene. We found the NodD3 amino acid sequence to be markedly diverged from the sequences of NodD1 and NodD2, which were more similar to the inducer-dependent NodD of another species, Rhizobium leguminosarum biovar viciae. The expression ofnodD3is not well understood, but involves at least SyrM, another positive activator related to the LysR-NodD family. One of the phenotypically mutant Tn insertions used in genetic studies of NodD3 nod regulation lacks NodD3 protein as determined by Western blots, but another expresses about 50–60% of the wild type level. The location of these Tn5 insertions substantially upstream of the open reading frame for NodD3 suggests importance of relatively distant regulatory sequences fornodD3expression. An insertion that did not cause a NodD3- phenotype is located in the extreme C-terminus of the protein coding region.