Institute of Genetics and Biochemistry, Biological Research Center, Hungarian Academy of Sciences, H-6701 Szeged, P. O. Box 521, Hungary.
Proc Natl Acad Sci U S A. 1986 Mar;83(6):1757-61. doi: 10.1073/pnas.83.6.1757.
A 47-base-pair (bp) conserved sequence in the 5'-flanking regions of three transcriptional units coding for nodulation functions (nodABC, nodEFG, and nodH) has been identified in Rhizobium meliloti strain 41. The conserved region contains subsequences of 7 bp, 5 bp, and 25 bp. The conserved 25-bp sequence was synthesized and used as a hybridization probe; three additional copies of the sequence were identified in R. meliloti 41; all three were localized in the 135-kb nod/nif region of the symbiotic megaplasmid. Nucleotide sequence analysis of the six regions revealed that all contained the 47-bp conserved sequence but, with one exception, adjacent DNA regions did not have long conserved DNA stretches. The position of the 47-bp region was about 200-240 bp upstream of the translational start codons of the three nod genes. This conserved sequence is present in several other Rhizobium species and located adjacent to nod genes. We have demonstrated the involvement of this sequence in the expression of nodulation functions, which suggests that these extended promoter regions may have a role in the coordinated regulation of nodulation genes.
在编码结瘤功能（nodABC、nodEFG 和 nodH）的三个转录单元的 5'侧翼区中，已经鉴定出一个由 47 个碱基对（bp）组成的保守序列。保守区域包含 7bp、5bp 和 25bp 的亚序列。保守的 25bp 序列被合成并用作杂交探针；在 Rhizobium meliloti 41 中还鉴定出另外三个序列；所有三个都定位于共生大质粒的 135kb nod/nif 区域。对六个区域的核苷酸序列分析表明，所有区域都包含 47bp 的保守序列，但除了一个例外，相邻的 DNA 区域没有长的保守 DNA 片段。47bp 区域的位置大约在三个 nod 基因的翻译起始密码子上游 200-240bp。该保守序列存在于其他几种根瘤菌中，并且位于 nod 基因的附近。我们已经证明了该序列参与了结瘤功能的表达，这表明这些扩展的启动子区域可能在结瘤基因的协调调控中发挥作用。
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