Article Abstract:
The chromosome and symbiosis-related genotypes of rhizopine-producing strains of Rhizobium meliloti and R. leguminosarum cannot be identified on the basis of chromosomal characteristics. Rhizopine synthesis is related to certain symbiotic plasmid genotypes but is independent of the genome of the host plant. Rhizopine synthesis (mos) genes show more variations than rhizopine catabolism (moc) genes. Less divergence in the R. leguminosarum mos and moc genes shows that they have evolved after R. meliloti.
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Article Abstract:
Diphosphopyridine-nucleotide-dependent malic enzyme (DME) of Rhizobium meliloti is needed for symbiotic nitrogen fixation since it forms a pathway in which malate is converted to acetyl-CoA in bacteroids. This enzyme shows maximal activity with NAD+ as cofactor but has reduced activity when NADP+ is used. Acetyl-CoA strongly inhibited DME activity but not TME activity. The dme gene was expressed in free-living cells and in nitrogen-fixing bacteroids while tme gene was repressed in bacteroids.
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Article Abstract:
Analysis of rhizopine scylloinosamine (SI) synthesis gene (mos) shows that the Rhizobium meliloti strain RM220-3 producing rhizopine SI in nodules contains three ORFs namely, ORF1, mosB and mosC arranged in a 3.9 kb operon unit. The L5-30 mos operon contains four ORFs and a construct developed from the L5-30 mos locus having truncated mosA gene produces SI instead of 3-O-MSI.
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