Croes C, Van Bastelaere E, DeClercq E, Eyers M, Vanderleyden J, Michiels K
F. A. Janssens Laboratory of Genetics, Catholic University of Leuven, Heverlee, Belgium.
Plasmid. 1991 Sep;26(2):83-93. doi: 10.1016/0147-619x(91)90048-2.
We have constructed a cosmid library of the Azospirillum brasilense Sp7 90-MDa plasmid (p90) and established the EcoRI restriction map of this plasmid. The central regions of cloned p90 DNA fragments from several recombinant cosmids were deleted by restriction endonuclease digestion and replaced by a DNA cassette encoding kanamycin resistance. Using these in vitro constructed deletions for marker exchange in Sp7, we made six different p90 deletion derivatives spanning all together 50% of the total length of p90. Comparison of the deletion derivatives with Sp7 for several properties revealed p90 loci involved in colony morphology, growth on minimal medium, motility, and adsorption to wheat roots. In analogy with the rhizobial symbiotic plasmids (pSym), we propose to denote the p90 plasmid as a rhizocoenotic plasmid (pRhico), carrying several genes involved in the A. brasilense-plant root interaction.
我们构建了巴西固氮螺菌Sp7 90-MDa质粒（p90）的黏粒文库，并建立了该质粒的EcoRI限制酶图谱。通过限制酶消化删除了几个重组黏粒中克隆的p90 DNA片段的中心区域，并用编码卡那霉素抗性的DNA盒进行替换。利用这些体外构建的缺失片段在Sp7中进行标记交换，我们制备了六种不同的p90缺失衍生物，它们总共覆盖了p90全长的50%。对缺失衍生物与Sp7的几种特性进行比较，揭示了p90中与菌落形态、在基本培养基上的生长、运动性以及对小麦根的吸附有关的基因座。类似于根瘤菌共生质粒（pSym），我们建议将p90质粒称为根际共栖质粒（pRhico），它携带几个参与巴西固氮螺菌与植物根相互作用的基因。
