title: A functional myo-inositol catabolism pathway is essential for rhizopine utilization by Sinorhizobium meliloti.
abstract: Rhizopine (L-3-O-methyl-scyllo-inosamine) is a symbiosis-specific compound found in alfalfa nodules induced by specific Sinorhizobium meliloti strains. It has been postulated that rhizobial strains able to synthesize and catabolize rhizopine gain a competitive advantage in the rhizosphere. The pathway of rhizopine degradation is analysed here. Since rhizopine is an inositol derivative, it was tested whether inositol catabolism is involved in rhizopine utilization. A genetic locus required for the catabolism of inositol as sole carbon source was cloned from S. meliloti. This locus was delimited by transposon Tn5 mutagenesis and its DNA sequence was determined. Based on DNA similarity studies and enzyme assays, this genetic region was shown to encode an S. meliloti myo-inositol dehydrogenase. Strains that harboured a mutation in the myo-inositol dehydrogenase gene (idhA) did not display myo-inositol dehydrogenase activity, were unable to utilize myo-inositol as sole carbon/energy source, and were unable to catabolize rhizopine. Thus, myo-inositol dehydrogenase activity is essential for rhizopine utilization in S. meliloti.
authors.affiliation: Department of Biological Sciences, Western, Michigan UniversityKalamazoo, MI 49008USA.
authors.forename: Mark P
authors.initials: MP
authors.lastname: Galbraith
authors.affiliation: Department of Biological Sciences, Western, Michigan UniversityKalamazoo, MI 49008USA.
authors.forename: Szi Fei
authors.initials: SF
authors.lastname: Feng
authors.affiliation: Department of Agronomy and Center for the Study of Nitrogen Fixation, University of Wisconsin- MadisonMadison, WI 53706USA.
authors.forename: James
authors.initials: J
authors.lastname: Borneman
authors.affiliation: Department of Agronomy and Center for the Study of Nitrogen Fixation, University of Wisconsin- MadisonMadison, WI 53706USA.
authors.forename: Eric W
authors.initials: EW
authors.lastname: Triplett
authors.affiliation: MSU-DOE Plant Research Laboratory, Department of Microbiology, NSF Center for Microbial Ecology, Michigan State UniversityEast Lansing, MI 48824USA.
authors.forename: Frans J
authors.initials: FJ
authors.lastname: de Bruijn
authors.affiliation: Department of Biological Sciences, Western, Michigan UniversityKalamazoo, MI 49008USA.
authors.forename: Silvia
authors.initials: S
authors.lastname: Rossbachl
mesh_terms: D000595:Amino Acid Sequence; D003001:Cloning, Molecular; D003227:Conjugation, Genetic; D005816:Genetic Complementation Test; D007294:Inositol / Q000031:analogs & derivatives* / Q000378:metabolism*; D000455:Medicago sativa / Q000382:microbiology; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D009243:NAD / Q000378:metabolism; D009586:Nitrogen Fixation / Q000235:genetics; D016366:Open Reading Frames / Q000235:genetics; D010641:Phenotype; D015183:Restriction Mapping; D012230:Rhizobiaceae / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D013401:Sugar Alcohol Dehydrogenases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism
chemical_list: D009243:NAD; C082577:rhizopine; D007294:Inositol; D013401:Sugar Alcohol Dehydrogenases; C021448:myo-inositol 2-dehydrogenase