The glcB locus of Rhizobium leguminosarum VF39 encodes an arabinose-inducible malate synthase.
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.
García-de los Santos
Alejandro
A
Programa de Genética Molecular de Plásmidos Bacterianos, Centro de Investigación sobre Fijación de Nitrógeno, Universidad Nacional Autónoma de México (UNAM), Apdo. Postal 565-A, Cuernavaca, Mor. México.
Morales
Alejandro
A
Baldomá
Laura
L
Clark
Scott R D
SR
Brom
Susana
S
Yost
Christopher K
CK
Hernández-Lucas
Ismael
I
Aguilar
Juan
J
Hynes
Michael F
MF
D000105:Acetyl Coenzyme A / Q000494:pharmacology; D000595:Amino Acid Sequence; D001089:Arabinose / Q000502:physiology; D001483:Base Sequence; D004251:DNA Transposable Elements; D005798:Genes, Bacterial; D016680:Genome, Bacterial; D008292:Malate Synthase / Q000096:biosynthesis / Q000235:genetics* / Q000302:isolation & purification; D008969:Molecular Sequence Data; D016296:Mutagenesis; D020161:Physical Chromosome Mapping; D010957:Plasmids; D011994:Recombinant Proteins / Q000302:isolation & purification; D012231:Rhizobium / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics; D017422:Sequence Analysis, DNA; D013559:Symbiosis; D014158:Transcription, Genetic; D001616:beta-Galactosidase / Q000378:metabolism
D004251:DNA Transposable Elements; D011994:Recombinant Proteins; D000105:Acetyl Coenzyme A; D001089:Arabinose; D008292:Malate Synthase; D001616:beta-Galactosidase