National Agricultural Research Center.
Microbes Environ. 2008;23(1):89-93. doi: 10.1264/jsme2.23.89.
We examined the nitrogenase reductase (nifH) genes of endophytic diazotrophic bacteria expressed in field-grown sweet potatoes (Ipomoea batatas L.) by reverse transcription (RT)-PCR. Gene fragments corresponding to nifH were amplified from mRNA obtained from the stems and storage roots of field-grown sweet potatoes several months after planting. Sequence analysis revealed that these clones were homologous to the nifH sequences of Bradyrhizobium, Pelomonas, and Bacillus sp. in the DNA database. Investigation of the nifH genes amplified from the genomic DNA extracted from these sweet potatoes also showed high similarity to various α-proteobacteria including Bradyrhizobium, β-proteobacteria, and cyanobacteria. These results suggest that bradyrhizobia colonize and express nifH genes not only in the root nodules of leguminous plants but also in sweet potatoes as diazotrophic endophytes.
我们通过反转录（RT）-PCR 检测了种植于田间的甘薯（Ipomoea batatas L.）中内生生氮还原酶（nifH）基因。从种植数月后的甘薯茎和块根中提取的 mRNA 中扩增出与 nifH 基因相对应的基因片段。序列分析表明，这些克隆与 DNA 数据库中 Bradyrhizobium、Pelomonas 和 Bacillus sp. 的 nifH 序列具有同源性。从这些甘薯中提取的基因组 DNA 扩增出的 nifH 基因的研究也表明，与包括 Bradyrhizobium、β-proteobacteria 和蓝细菌在内的各种α-变形菌具有高度相似性。这些结果表明，慢生根瘤菌不仅在豆科植物的根瘤中，而且在作为固氮内生菌的甘薯中也能定植并表达 nifH 基因。
