AEM
Home Help [Feedback] [For Subscribers] [Archive] [Search] [Contents]
This Article
Right arrow Full Text
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrowReprints and Permissions
Right arrow Copyright Information
Right arrow Books from ASM Press
Right arrow MicrobeWorld
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Yasuta, T.
Right arrow Articles by Minamisawa, K.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Yasuta, T.
Right arrow Articles by Minamisawa, K.
Agricola
Right arrow Articles by Yasuta, T.
Right arrow Articles by Minamisawa, K.

 Previous Article  |  Next Article 

Applied and Environmental Microbiology, November 2001, p. 4999-5009, Vol. 67, No. 11
0099-2240/01/$04.00+0   DOI: 10.1128/AEM.67.11.4999-5009.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.

DNA Sequence and Mutational Analysis of Rhizobitoxine Biosynthesis Genes in Bradyrhizobium elkanii

Tsuyoshi Yasuta,1,dagger Shin Okazaki,1 Hisayuki Mitsui,1 Ken-Ichi Yuhashi,2,Dagger Hiroshi Ezura,3 and Kiwamu Minamisawa1,*

Institute of Genetic Ecology1 and Bio-oriented Technology Research Advancement Institution (BRAIN), Institute of Genetic Ecology,2 Tohoku University, Katahira, Aoba-ku, Sendai 980-8577, and Institute of Agriculture and Forestry, Gene Experiment Center, University of Tsukuba, Tsukuba 305-8572,3 Japan

Received 4 June 2001/Accepted 31 August 2001

We cloned and sequenced a cluster of genes involved in the biosynthesis of rhizobitoxine, a nodulation enhancer produced by Bradyrhizobium elkanii. The nucleotide sequence of the cloned 28.4-kb DNA region encompassing rtxA showed that several open reading frames (ORFs) were located downstream of rtxA. A large-deletion mutant of B. elkanii, USDA94Delta rtx::Omega 1, which lacks rtxA, ORF1 (rtxC), ORF2, and ORF3, did not produce rhizobitoxine, dihydrorhizobitoxine, or serinol. The broad-host-range cosmid pLAFR1, which contains rtxA and these ORFs, complemented rhizobitoxine production in USDA94Delta rtx::Omega 1. Further complementation experiments involving cosmid derivatives obtained by random mutagenesis with a kanamycin cassette revealed that at least rtxA and rtxC are necessary for rhizobitoxine production. Insertional mutagenesis of the N-terminal and C-terminal regions of rtxA indicated that rtxA is responsible for two crucial steps, serinol formation and dihydrorhizobitoxine biosynthesis. An insertional mutant of rtxC produced serinol and dihydrorhizobitoxine but no rhizobitoxine. Moreover, the rtxC product was highly homologous to the fatty acid desaturase of Pseudomonas syringae and included the copper-binding signature and eight histidine residues conserved in membrane-bound desaturase. This result suggested that rtxC encodes dihydrorhizobitoxine desaturase for the final step of rhizobitoxine production. In light of results from DNA sequence comparison, gene disruption experiments, and dihydrorhizobitoxine production from various substrates, we discuss the biosynthetic pathway of rhizobitoxine and its evolutionary significance in bradyrhizobia.

* Corresponding author. Mailing address: Institute of Genetic Ecology, Tohoku University, Katahira, Aoba-ku, Sendai 980-8577, Japan. Phone: 81-22-217-5684. Fax: 81-22-263-9845. E-mail: kiwamu{at}ige.tohoku.ac.jp.

dagger Present address: Research Center for Advanced Waste and Emission Management, Nagoya University, Chikusa-ku, Nagoya, Aichi 464-8603, Japan.

Dagger Present address: Plant Biotechnology Institute, Ibaraki Agriculture Center, Ago, Iwama, Nishi-Ibaraki 319-0292, Japan.

Applied and Environmental Microbiology, November 2001, p. 4999-5009, Vol. 67, No. 11
0099-2240/01/$04.00+0   DOI: 10.1128/AEM.67.11.4999-5009.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.


This article has been cited by other articles:



Home Help [Feedback] [For Subscribers] [Archive] [Search] [Contents]
J. Bacteriol. Microbiol. Mol. Biol. Rev. Eukaryot. Cell All ASM Journals

Copyright © 2001 by the American Society for Microbiology. All rights reserved.