The subcellular organization of strictosidine biosynthesis in Catharanthus roseus epidermis highlights several trans-tonoplast translocations of intermediate metabolites.

Catharanthus roseus synthesizes a wide range of valuable monoterpene indole alkaloids, some of which have recently been recognized as functioning in plant defence mechanisms. More specifically, in aerial organ epidermal cells, vacuole-accumulated strictosidine displays a dual fate, being either the precursor of all monoterpene indole alkaloids after export from the vacuole, or the substrate for a defence mechanism based on the massive protein cross-linking, which occurs subsequent to organelle membrane disruption during biotic attacks. Such a mechanism relies on a physical separation between the vacuolar strictosidine-synthesizing enzyme and the nucleus-targeted enzyme catalyzing its activation through deglucosylation.

Spatial organization of the vindoline biosynthetic pathway in Catharanthus roseus.

Vindoline constitutes the main terpenoid indole alkaloid accumulated in leaves of Catharanthus roseus, and four genes involved in its biosynthesis have been identified. However, the spatial organization of the tabersonine-to-vindoline biosynthetic pathway is still incomplete. To pursue the characterization of this six-step conversion, we illustrated, with in situ hybridization, that the transcripts of the second biosynthetic enzyme, 16-hydroxytabersonine 16-O-methyltransferase (16OMT), are specifically localized to the aerial organ epidermis.

Two distinct intracellular Ca2+-release components act in opposite ways in the regulation of the auxin-dependent MIA biosynthesis in Catharanthus roseus cells.

Calcium-mediated signalling is ubiquitous in both animals and plants. Changes in cytoplasmic free Ca(2+) concentration couple diverse arrays of stimuli to their specific responses, the specificity of the stimulus being determined by integrated actions between multiple Ca(2+) mobilization pathways. In this work, a pharmacological approach is reported, aimed at deciphering the role of calcium as a second messenger in the transduction pathway leading to the inhibitory effect of 2,4-dichlorophenoxyacetic acid (2,4-D), in regulating monoterpene indole alkaloid (MIA) biosynthesis in Catharanthus roseus cells.

Competition between elastase and related proteases from human neutrophil for binding to alpha1-protease inhibitor.

The protease-antiprotease imbalance that is characteristic of most inflammatory lung disorders depends on the spatial-temporal regulation of active inhibitor and protease concentrations in lung secretions. We have studied the competition between the three main serine proteases from human neutrophil primary granules in their binding to alpha1-Pi, the main serine proteases inhibitor in lung secretions. Elastase was the only target of alpha1-Pi when identical molar amounts of purified inhibitor and the three proteases were tested together.