Pandolfini T, Storlazzi A, Calabria E, Defez R, Spena A
Faculty of Science, University of Verona, Verona, Italy.
Mol Microbiol. 2000 Mar;35(6):1326-34. doi: 10.1046/j.1365-2958.2000.01810.x.
Agrobacterium rhizogenes transfers DNA (T-DNA) from its Ri plasmid to plant cells. All T-DNA genes are expressed in plant cells. The rolA gene is the only T-DNA gene that contains an intron in the untranslated leader region of its mRNA. This paper shows that (i) the rolA gene is also transcribed in bacteria; (ii) the 85 bp corresponding to the spliceosomal intron drives prokaryotic gene expression in agrobacteria, in free-living rhizobia and in bacteroids within root nodules; and (iii) promoter activity is abolished by the deletion of 63 bp from its 5' end and is reduced by mutations changing its sequence near the putative -10 region. The expression pattern of a chimeric reporter gene shows that, in free-living bacteria, gene expression takes place during the exponential phase of growth and increases at the onset of the stationary phase. Within root nodules, reporter gene expression occurs in the invasion, nitrogen fixing and senescent zones.
发根农杆菌将其Ri质粒中的DNA（T-DNA）转移至植物细胞。所有T-DNA基因均在植物细胞中表达。rolA基因是唯一在其mRNA非翻译前导区含有一个内含子的T-DNA基因。本文表明：（i）rolA基因也在细菌中转录；（ii）对应于剪接体内含子的85 bp片段在农杆菌、自由生活的根瘤菌以及根瘤内的类菌体中驱动原核基因表达；（iii）从其5'端缺失63 bp会消除启动子活性，而改变其假定-10区附近序列的突变会使其活性降低。嵌合报告基因的表达模式表明，在自由生活的细菌中，基因表达发生在生长的指数期，并在稳定期开始时增加。在根瘤内，报告基因表达发生在侵入区、固氮区和衰老区。
