glcB locus of Rhizobium leguminosarum VF39 encodes an arabinose-inducible malate synthase

• Published in: Canadian journal of microbiology Vol. 48; no. 10; pp. 922 - 932
• Main Authors: Garcia-de los Santos, A, Morales, A, Baldoma, L, Clark, S.R.D, Brom, S, Yost, C.K, Hernandez-Lucas, I, Aguilar, J, Hynes, M.F
• Format: Journal Article
• Language: English
• Published: Ottawa, Canada NRC Research Press 01.10.2002; National Research Council of Canada; Canadian Science Publishing NRC Research Press
• Subjects: Acetyl Coenzyme A - pharmacology; Amino Acid Sequence; arabinose; Arabinose - physiology; Bacteria; Bacteriology; Base Sequence; beta-Galactosidase - metabolism; Biological and medical sciences; DNA Transposable Elements; E coli; enzyme activity; Enzymes; Flowers & plants; Fundamental and applied biological sciences. Psychology; gene expression; Genes; Genes, Bacterial; genetic regulation; Genetics; Genome, Bacterial; glycolic acid; glyoxylic acid; loci; Malate Synthase - biosynthesis; Malate Synthase - genetics; Malate Synthase - isolation & purification; Metabolism; Microbiology; Microorganisms; Molecular Sequence Data; Mutagenesis; mutants; Mutation; Nitrogen fixation; nodulation; nucleotide sequences; oxo-acid-lyases; Physical Chromosome Mapping; Pisum sativum; Plasmids; Recombinant Proteins - isolation & purification; Rhizobium - drug effects; Rhizobium - enzymology; Rhizobium - genetics; Rhizobium leguminosarum; Sequence Analysis, DNA; Symbiosis; Transcription, Genetic; Genome organization; Enzyme; Induction; Lyases; Rhizobium leguminosarum; Oxo-acid-lyases; Carbon-carbon lyases; Arabinose; Regulation(control); Malate synthase; Bacteria; Rhizobiaceae; Locus; Glyoxylate cycle
• ISSN: 0008-4166; 1480-3275
• DOI: 10.1139/w02-091

In the course of a study conducted to isolate genes upregulated by plant cell wall sugars, we identified an arabinose-inducible locus from a transcriptional fusion library of Rhizobium leguminosarum VF39, carrying random insertions of the lacZ transposon Tn5B22. Sequence analysis of the locus disrupted by the transposon revealed a high similarity to uncharacterized malate synthase G genes from Sinorhizobium meliloti, Agrobacterium tumefaciens, and Mesorhizobium loti. This enzyme catalyzes the condensation of glyoxylate and acetyl-CoA to yield malate and CoA and is thought to be a component of the glyoxylate cycle, which allows microorganisms to grow on two carbon compounds. Enzyme assays showed that a functional malate synthase is encoded in the glcB gene of R. leguminosarum and that its expression is induced by arabinose, glycolate, and glyoxylate. An Escherichia coli aceB glcB mutant, complemented with the R. leguminosarum PCR-amplified gene, recovered malate synthase activity. A very similar genome organization of the loci containing malate synthase and flanking genes was observed in R. leguminosarum, S. meliloti, and A. tumefaciens. Pea plants inoculated with the glcB mutant or the wild-type strain showed no significant differences in nitrogen fixation. This is the first report regarding the characterization of a mutant in one of the glyoxylate cycle enzymes in the rhizobia.Key words: Rhizobium, malate synthase, glyoxylate cycle, arabinose metabolism.