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The role of integraase on the evolution of nod genes of Rhizobium

整合酶在根瘤菌nod基因进化中的作用

基本信息

批准号：
09680678
负责人：
UCHIUMI Toshiki
金额：
$ 2.24万
依托单位：
Kagoshima University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1997
资助国家：
日本
起止时间：
1997 至 1999
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-09680678/
关键词：
Rhizobium lysogenic phage tRNA integrase Agrobacterium nod gene symbiotic plasmid host range インテグレーション

项目摘要

The integrase/tRNA gene unit, which mediates site specific recombination and is often found on the genomes of lysogenic phages, was possible to promote the rearrangement or horizontal transfer of nod genes of rhizobia. Recently, the integrase/tRNA gene unit was found on the transferable large DNA fragment including nod genes and was named symbiotic island of Rhizobium. The diversity of rhizobia from tropical legumes may be an evidence of the frequent rearrangement or horizontal transfer of nod genes. The PCR-primer sets for detection of the integrase/tRNA gene unit were designed based on the DNA sequences of integrases of lysogenic phages and tRNAs. However, the integrase/tRNA gene unit could not be found on the genomes of the topical rhizobium stains isolated from soy bean nodules cultivated in Thailand by PCR.The symbiotic plasmid (pSym) of the clover-Rhizobium strain 4S was transferred to Agrobacterium stain A136 by conjugation. Some of the transconjugant Agrobacterium stains were able to nodulate not only on the normal host, white clover, but also on alfalfa, hairy vetch, and siratro. A characteristic bacteroid differentiation was observed in clover and alfalfa nodules induced by the tansconjugants, although nitrogen-fixing ability was not found. Pulsed field gel electrophoresis revealed that a large fragment including nod genes on the pSym could be translocated on the Agrobacterium genome, however, it is not clear whether the translocation was mediated by the integrase/tRNA gene unit on the pSym or not.

整合酶/tRNA基因单元介导位点特异性重组，通常存在于溶原噬菌体的基因组中，可能促进根瘤菌nod基因的重排或水平转移。最近，在包括nod基因的可转移大DNA片段上发现了整合酶/tRNA基因单元，并将其命名为根瘤菌的共生岛。热带豆科植物根瘤菌的多样性可能是结节基因频繁重排或水平转移的证据。用于检测整合酶/tRNA基因单元的PCR引物组是根据溶原噬菌体和tRNA整合酶的DNA序列设计的。然而，通过PCR，在从泰国种植的大豆根瘤中分离的局部根瘤菌菌株的基因组上找不到整合酶/tRNA基因单元。将三叶草-根瘤菌菌株4S的共生质粒（pSym）通过接合转移至农杆菌菌株A136。一些转接合农杆菌染色剂不仅能够在正常宿主白三叶草上结瘤，而且还能在苜蓿、毛野豌豆和 siratro 上结瘤。尽管没有发现固氮能力，但在由转缀合物诱导的三叶草和苜蓿根瘤中观察到了特征性的类菌分化。脉冲场凝胶电泳显示pSym上包含nod基因的大片段可以在农杆菌基因组上易位，然而，尚不清楚易位是否由pSym上的整合酶/tRNA基因单元介导。