Das A, Khanuja S P, Lodha M L
Division of Biochemistry, Indian Agricultural Research Institute, New Delhi, India.
Indian J Exp Biol. 1997 Dec;35(12):1331-5.
Plasmids containing Rhizobium meliloti symbiotic promoters P1 (promoter of nifHDK) and P2 (promoter of fixABCX) when mobilized into the cells of Azorhizobium caulinodans strain IRBG 46 showed strong expression of these promoters under free-living microaerobic as well as symbiotic conditions. Under free-living conditions microaerobiosis (3% or less O2) was found to be sufficient to activate these promoters; expression being higher at 1% than at 3% O2 concentration. Under symbiotic conditions the expression was much more stronger-with bacteroids in stem nodules showing higher expression than those in root nodules. Under both the conditions expression of the promoters in the native R. meliloti strain Rm102F34 was lower than that in the A. caulinodans strain IRBG 46. The results suggest a functional homology of these promoters in the heterologous background of A. caulinodans.
含有苜蓿根瘤菌共生启动子P1（nifHDK的启动子）和P2（fixABCX的启动子）的质粒，当导入茎瘤固氮根瘤菌菌株IRBG 46的细胞中时，在自由生活的微需氧条件以及共生条件下均显示出这些启动子的强表达。在自由生活条件下，发现微需氧（氧气含量为3%或更低）足以激活这些启动子；在氧气浓度为1%时的表达高于3%时。在共生条件下，表达要强得多——茎瘤中的类菌体显示出比根瘤中的类菌体更高的表达。在这两种条件下，天然苜蓿根瘤菌菌株Rm102F34中启动子的表达均低于茎瘤固氮根瘤菌菌株IRBG 46中的表达。结果表明这些启动子在茎瘤固氮根瘤菌的异源背景中具有功能同源性。
