HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by Delgado, M. J. Articles by Bedmar, E. J. Search for Related Content PubMed PubMed Citation Articles by Delgado, M. J. Articles by Bedmar, E. J. Agricola Articles by Delgado, M. J. Articles by Bedmar, E. J.

Functional characterization of the Bradyrhizobium japonicum modA and modB genes involved in molybdenum transport

Departamento de Microbiología del Suelo y Sistemas Simbióticos, Estación Experimental del Zaidín, CSIC, PO Box 419, 18080 Granada, Spain

Correspondence
María J. Delgado
mdelgado{at}eez.csic.es

A modABC gene cluster that encodes an ABC-type, high-affinity molybdate transporter from Bradyrhizobium japonicum has been isolated and characterized. B. japonicum modA and modB mutant strains were unable to grow aerobically or anaerobically with nitrate as nitrogen source or as respiratory substrate, respectively, and lacked nitrate reductase activity. The nitrogen-fixing ability of the mod mutants in symbiotic association with soybean plants grown in a Mo-deficient mineral solution was severely impaired. Addition of molybdate to the bacterial growth medium or to the plant mineral solution fully restored the wild-type phenotype. Because the amount of molybdate required for suppression of the mutant phenotype either under free-living or under symbiotic conditions was dependent on sulphate concentration, it is likely that a sulphate transporter is also involved in Mo uptake in B. japonicum. The promoter region of the modABC genes has been characterized by primer extension. Reverse transcription and expression of a transcriptional fusion, P_modA–lacZ, was detected only in a B. japonicum modA mutant grown in a medium without molybdate supplementation. These findings indicate that transcription of the B. japonicum modABC genes is repressed by molybdate.

The GenBank/EMBL/DDBJ accession number for the B. japonicum mod gene sequence reported in this paper is AF446208, and this corresponds to ORFs blr8160, blr8161 and blr8162 from the recently sequenced B. japonicum USDA110 genome (see http://www.kazusa.jp/rhizobase/).

This article has been cited by other articles:

				J. Wiethaus, A. Wirsing, F. Narberhaus, and B. Masepohl Overlapping and Specialized Functions of the Molybdenum-Dependent Regulators MopA and MopB in Rhodobacter capsulatus J. Bacteriol., December 15, 2006; 188(24): 8441 - 8451. [Abstract] [Full Text] [PDF]

				T. H. Mauchline, J. E. Fowler, A. K. East, A. L. Sartor, R. Zaheer, A. H. F. Hosie, P. S. Poole, and T. M. Finan Mapping the Sinorhizobium meliloti 1021 solute-binding protein-dependent transportome PNAS, November 21, 2006; 103(47): 17933 - 17938. [Abstract] [Full Text] [PDF]