INDUCTION OF NITROGEN-FIXING NODULES ON CLOVER REQUIRES ONLY 32 KILOBASE PAIRS OF DNA FROM THE RHIZOBIUM-TRIFOLII SYMBIOSIS PLASMID
INDUCTION OF NITROGEN-FIXING NODULES ON CLOVER REQUIRES ONLY 32 KILOBASE PAIRS OF DNA FROM THE RHIZOBIUM-TRIFOLII SYMBIOSIS PLASMID
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DOI：
10.1128/jb.170.9.3793-3802.1988
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发表时间：
1988-09-01
影响因子：
3.2
通讯作者：
KUEMPEL, PL
中科院分区：
文献类型：
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作者：
INNES, RW;HIROSE, MA;KUEMPEL, PL
使用体内和体外方法产生来自三叶根瘤菌共生质粒pRt843a的重叠亚克隆。通过将亚克隆引入消除其共生质粒的三叶草ANU843衍生物中并测试转接合体菌株在三叶草上诱导固氮根瘤的能力来测定亚克隆的共生表型。发现来自 pRt843a 的一个跨越 32 KB DNA 的亚克隆可以恢复固氮能力。该亚克隆包括所有已知的R. trifolli ANU843 结瘤基因和固氮酶结构基因nifHDK。此外，通过DNA-DNA杂交，在这个32kb的亚克隆中鉴定出了与其他固氮细菌的fixABC、nifA、nifB、nifE和nifN基因同源的区域。该亚克隆的转座子诱变证实，含有这些 nif 和 fix 基因的区域是三叶草上固氮根瘤诱导所必需的。此外，还发现位于nifK基因下游5 kb的区域是诱导固氮根瘤所必需的。在后一个区域中未检测到与已知 nif 和 fix 基因的同源性。
Overlapping subclones from Rhizobium trifolii symbiosis plasmid pRt843a were generated by using in vivo and in vito methods. Subclones were assayed for symbiotic phenotype by introducing them into a derivative of R. trifolii ANU843 cured of its symbiosis plasmid and testing the transconjugant strains for the ability to induce nitrogen-fixing nodules on clover. One subclone spanning 32 kilobase pairs (kb) of DNA from pRt843a was found to restore nitrogen fixation ability. This subclone included all known nodulation genes of R. trifolli ANU843 and the nitrogenase structural gene nifHDK. In addition, regions homologous to fixABC, nifA, nifB, nifE, and nifN genes of other nitrogen-fixing bacteria were identified in this 32-kb subclone by DNA-DNA hybridization. Transposon mutagenesis of this subclone confirmed that regions containing these nif and fix genes were required for indution of nitrogen-fixing nodules on clover. In addition, a region located 5 kb downstream of the nifK gene was found to be required for induction of nitrogen-fixing nodules. No homology to known nif and fix genes could be detected in this latter region.