【摘要】 对巴西固氮螺菌ｄｒａＴＧ上游区域进行了全序列分析，结果表明该区域除了编码部分ｎｉｆＨ基因外（ｎｉｆＨ与ｄｒａＴＧ转录方向相反），不编码任何其它已知的基因。但在该区域发现了一些可能的调控序列，它们包括上游激活序列（ＵＡＳ）、下游启动子组份（ＤＰＥ）和富Ａ＋Ｔ区。这说明：ｎｉｆＨ与ｄｒａＴ间的区域可能主要起调控功能而非编码功能；ｄｒａ操纵元（ｏｐｅｒｏｎ）的启动子很可能是ＲｐｏＮ－依赖型。用ｐＡＦ３００做载体，构建了ｄｒａＴ∷ｃａｍ转录融合质粒ｐＡＴ１，并通过检测Ｃｍｒ以检测ｄｒａＴ在大肠杆菌和巴西固氮螺菌中的表达，结果表明ｄｒａＴ在ＬＤ丰富培养基上，好氧条件下，只在巴西固氮螺菌中才表达。这说明，ｄｒａＴ的转录需要某种大肠杆菌中没有的因子，同时也表明ｄｒａＴＧ上游区域有启动子功能。利用启动子探针质粒载体ｐＣＢ１８２，构建了ｄｒａＴ∷ｌａｃＺ转录融合质粒ｐＣＴ１。在大肠杆菌中测定肺炎克氏杆菌ＮｉｆＡ对ｄｒａＴ∷ｌａｃＺ的转录激活作用。结果表明ｎｉｆＡ并不参与ｄｒａＴ的转录调控。更多还原

【Abstract】 From Azospirillum brasilense Yu62,we cloned and sequenced the upstream region of draTG .No identified genes were found in this region except for portion of nifH,which is transcribed divergently from draTG.However,some potential regulatory elements were found,which include downstream promoter elements (DPE),upstream activitor sequences (UAS),and A+T rich regions.It suggests that the region between draT and nifH might be a regulatory region rather than an encoding region,and the promoter of dra operon would probably be a RpoN-dependent promoter.A draT∷cam transcriptional fusion plasmid pAT1 was constructed in pAF300.The expression of draT was studied in Escherichia coli and A.brasilense by Cm r assay.The result showed that draT could be transcribed in A.brasilense but not in E.coli while grown aerobically on LD plate.It suggests that the transcription of draT needs some factors which are absent in E.coli ,and the draT upstream region has the promoter function.Using promoter probe vector pCB182,a draT∷lacZ transcriptional fusion plasmid pCT1 was constructed.β galactosidase activity was determined in vivo in E.coli ,in the presence or absence of NifA of Klebsiella pneumoniae ,respectively.The results demonstrated that NifA wasn’t involved in the transcription of draTG.更多还原