1887

Abstract

A bv. VF39 gene () encoding a γ-aminobutyrate (GABA) aminotransferase was identified, cloned and characterized. This gene is thought to be involved in GABA metabolism via the GABA shunt pathway, a theoretical bypass of the 2-oxoglutarate dehydrogenase complex. Mutants in are still able to grow on GABA as a sole carbon and nitrogen source. 2-Oxoglutarate-dependent GABA aminotransferase activity is absent in these mutants, while pyruvate-dependent activity remains unaffected. This indicates that at least two enzymes with different substrate specifities are involved in the GABA metabolism of bv. VF39. The promoter was cloned into a newly constructed, stable promoter-probe vector pJP2, suitable for the study of transcriptional GUS fusions in free-living bacteria and during symbiosis. Under free-living conditions the promoter is induced by GABA and repressed by succinate. Transcriptional regulation is mediated by GabR in a repressor-like manner. During symbiosis with the pea host plant is induced and highly expressed in the symbiotic zone. Nodules induced by mutants, however, are still effective in nitrogen fixation.

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2002-02-01
2020-01-23
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