Rhizobium meliloti Genes Encoding Catabolism of Trigonelline Are Induced under Symbiotic Conditions.
Open Access
- 1 December 1990
- journal article
- Published by Oxford University Press (OUP) in Plant Cell
- Vol. 2 (12), 1157-1170
- https://doi.org/10.1105/tpc.2.12.1157
Abstract
Rhizobium meliloti trc genes controlling the catabolism of trigonelline, a plant secondary metabolite often abundant in legumes, are closely linked to nif-nod genes on the symbiotic megaplasmid pSym [Boivin, C., Malpica, C., Rosenberg, C., Denarie, J., Goldman, A., Fleury, V., Maille, M., Message, B., and Tepfer, D. (1989). In Molecular Signals in the Microbe-Plant Symbiotic and Pathogenic Systems. (Berlin: Springer-Verlag), pp. 401-407]. To investigate the role of trigonelline catabolism in the Rhizobium-legume interaction, we studied the regulation of trc gene expression in free-living and in endosymbiotic bacteria using Escherichia coli lacZ as a reporter gene. Experiments performed with free-living bacteria indicated that trc genes were organized in at least four transcription units and that the substrate trigonelline was a specific inducer for three of them. Noninducing trigonelline-related compounds such as betaines appeared to antagonize the inducing effect of trigonelline. None of the general or symbiotic regulatory genes ntrA, dctB/D, or nodD seemed to be involved in trigonelline catabolism. trc fusions exhibiting a low basal and a high induced [beta]-galactosidase activity when present on pSym were used to monitor trc gene expression in alfalfa tissue under symbiotic conditions. Results showed that trc genes are induced during all the symbiotic steps, i.e., in the rhizosphere, infection threads, and bacteroids of alfalfa, suggesting that trigonelline is a nutrient source throughout the Rhizobium-legume association.Keywords
This publication has 17 references indexed in Scilit:
- Rhizobium meliloti nodD genes mediate host-specific activation of nodABCJournal of Bacteriology, 1990
- Current ReviewPhenolic Compounds as Regulators of Gene Expression in Plant-Microbe InteractionsMolecular Plant-Microbe Interactions®, 1990
- A Chalcone and Two Related Flavonoids Released from Alfalfa Roots Induce nod Genes of Rhizobium melilotiPlant Physiology, 1989
- Analysis of C4‐dicarboxylate transport genes in Rhizobium melilotiMolecular Microbiology, 1989
- Rhizobium-legume nodulation: Life together in the undergroundCell, 1989
- Characterization of three choline transport activities in Rhizobium meliloti: modulation by choline and osmotic stressJournal of Bacteriology, 1989
- Pseudomonas solanacearum genes controlling both pathogenicity on tomato and hypersensitivity on tobacco are clusteredJournal of Bacteriology, 1987
- A Plant Flavone, Luteolin, Induces Expression of Rhizobium meliloti Nodulation GenesScience, 1986
- Construction of a broad host range cosmid cloning vector and its use in the genetic analysis of Rhizobium mutantsGene, 1982
- Genes controlling early and late functions in symbiosis are located on a megaplasmid in Rhizobium melilotiMolecular Genetics and Genomics, 1981