Arlette Goldmann

Tropane derivatives from Calystegia sepium.

Abstract A family of novel polyhydroxy- nor -tropanes is described. Three of their structures were determined by mass spectrometry and 1 H and 13 C NMR spectroscopy. These calystegins occur in two species of the Convolvulaceae and in Atropa belladonna . Their potential ecological significance is discussed.

The stachydrine catabolism region in Sinorhizobium meliloti encodes a multi-enzyme complex similar to the xenobiotic degrading systems in other bacteria.

Stachydrine (proline betaine) can be used by Sinorhizobium meliloti as a source of carbon and nitrogen. Catabolism depends on an initial N-demethylation, after which the resultant N-methyl proline enters general metabolism. Deletion and insertion mutagenesis demonstrated that the information necessary for catabolism is carried on the symbiotic plasmid (pSym) distal to nodD2 and the nod-nif cluster. Sequencing of an 8.5kb fragment spanning this region revealed four open reading frames with functional homology to known proteins, including a putative monooxygenase and a putative NADPH-FMN-reductase, which were shown by insertional and frame-shift mutagenesis to be necessary for stachydrine catabolism. Other open reading frames, encoding a putative flavoprotein and a repressor, were judged not to be required for stachydrine catabolism, since they were not included in a fragment capable of complementing a deletion of the entire stc region. Sequence and mutagenesis data suggest that stachydrine is demethylated by an iron-sulfur monooxygenase of the Rieske type with a requirement for a specific reductase. The stc catabolic cluster, therefore, resembles xenobiotic degradation in other bacteria and recalls rhizopine catabolism in S. meliloti. Stachydrine appears to have multiple roles in osmoprotection, nutrition and nodulation. Genes involved in stachydrine catabolism are also necessary for carnitine degradation; thus, they could be important in the catabolism of a variety of root exudates and mediate other relationships.

Antibody against octopine dehydrogenase from crown gall tumor tissue, a tool in studies of plant cell transformation

1. Introduction The enzymes octopine and nopaline dehydrogenase are responsible for the synthesis of the unusual amino acid derivatives octopine and nopaline, specific for crown-gall tumors [l-4]. The nature of the enzyme synthesized is determined by the Ti-plasmid har- boured in the

Metabolic Signals in the Rhizosphere: Catabolism of Calystegins and Trigonelline by Rhizobium Meliloti

Bacteria that associate with plants are generally saprophitic. They compete with other heterotrophic organisms for the products of plant photosynthesis. In certain cases their relationships with plants are commensalistic or symbiotic. Transfer of energy from plants to bacteria takes place primarily in the soil through the release of exudates by roots and the shedding of aerial and subterranean plant parts: leaves and roots (e.g. root cap). The ability to catabolize substances produced by the plant is surely crucial to the survival of soil bacteria, and these substances are likely objects of intense competition (Nutman 1965). Plants produce a variety of secondary metabolites that are potential carbon and/or nitrogen sources for soil bacteria. It would seem logical that bacteria would evolve catabolic functions to degrade and utilize these metabolites, and that exclusive nutritional relationships could co-evolve, i.e. plants would produce exotic metabolites, not generally catabolized by microorganisms, and certain bacteria would benefit from these substances, which we have called nutritional mediators (Tepfer et al 1988), by evolving the corresponding catabolic functions. These nutritional mediators can be thought of as signals that at the same time trigger and fuel catabolism leading to growth. It is also logical that selective microbial growth would be important to the specificity of plant-microorganism interactions.