A method for preparing elicitor-responsive protoplasts from grapevine cells kept in suspension culture was established. The protoplasts were employed in order to perform transient gene expression experiments produced by externally added plasmids. Using the gene coding for bacterial beta-glucuronidase as the reporter gene, the transient expression under the control of various promoters of stilbene synthase genes were analyzed. The elicitor-responsiveness of promoters from grapevine genes and heterologous promoters were assayed: the grapevine stilbene synthase gene VST-1 and pine stilbene synthase genes PST-1, PST-2 and PST-3. Compared to the expression effected by the cauliflower mosaic virus 35S RNA-promoter, the stilbene synthase promoters caused a 2-5-fold increase in GUS-activity. Incubation of transformed protoplasts with fungal cell wall further stimulated the stilbene synthase promoters but not the 35S RNA-promoter. An even more pronounced differentiation between the promoters was observed when cGMP was included in the transient expression assays. Instead of treating transformed protoplasts with fungal cell wall we administered simultaneously cGMP and the plasmid to be tested. The cGMP-responsive increase was (a) specific concerning the nucleotide applied, (b) characteristic of grapevine protoplasts, and (c) not seen with shortened promoter-GUS constructs or GUS under the control of the 35S RNA-promoter. The highest cGMP-dependent response to stress was shown by the promoter of the grapevine stilbene synthase gene VST-1.

Acyltransferases↗

PubMedDate not supplied

Studies supporting the concept of glyoxyperoxisomes as intermediary organelles in transformation of glyoxysomes into peroxisomes.

Intermediary forms of microbodies, glyoxyperoxisomes, are most likely synthesized at the stage of replacement of glyoxysomes by peroxisomes during the greening of fatstoring cells of cucumber cotyledons. This hypothesis is supported by three lines of results: 1. The levels of both glycollate oxidase and malate synthase are increased in the microbody fractions upon illumination of cotyledons. 2. Both peroxisomal and glyoxysomal marker enzymes are localized in organelles which exhibit the same buoyant densities. 3. De novo synthesis of malate synthase takes place even when irradiation already leads to a drastic increase of glycollate oxidase. The amount of malate synthase synthesized is almost identical in the light-induced system and in the dark control.

Alcohol Oxidoreductases↗