No abstract

Total soluble phenols, soluble flavanols, (+)-catechin, ferulic acid and 1-O-feruloyl-beta-d-glucose were analyzed during the development of a strawberry (Fragariaxananassa, cv. Chandler) callus culture. The time-course changes of the different phenols assayed were well correlated with callus growth and morphology. The changes in polyphenol oxidase (EC 1.10.3.1-2) and beta-glucosidase (EC 3.2.1.21) activities in the callus were also examined. The total phenol, soluble flavanols and (+)-catechin contents were high during the preexponential and exponential phases of growth. The subsequent decrease in (+)-catechin concentration coincided with high levels of polyphenol oxidase activity. The 1-O-feruloyl-beta-d-glucose content was highest as callus growth ceased, and its subsequent decrease was accompanied by the increased production of ferulic acid. This increase in ferulic acid was accompanied by an increase in beta-glucosidase activity. The ferulic acid content decreased at the end of culture, when callus growth had stopped and showed clear symptoms of senescence. This decrease in the ferulic acid concentration was accompanied by an increase in the levels of ferulic acid bound to cell wall components.

SUMMARYSuspension cell cultures of grapevine {Vitis vinifera, cv. Monastrell) treated with an elicitor (cellulase, Onozuka R-10) from Trichoderma viride showed a hypersensitive-like response. This was characterized by cell plasmolysis and was accompanied by localized cell death, which was concomitant with cell culture browning, itself probably due to an activation of oxidative phenolic metabolism driven by a large increase in endogenous levels of H.^O2. In addition to these responses, the treatment of cell cultures with the elicitor produced an increase in amounts of benzoic acid and of resveratrol, the latter a potent phytoalexin of grapevines. This hypersensitive-like response was specific since none of the above responses was obtained with other cell wall-degrading enzymes from several sources, or with inocula of either mycelial extracts or culture filtrates of Botrytis cinerea. These results are discussed in the light of a disease-resistance reaction induced in grapevine cells by a product of T. viride, a fungal agent characterized by its effective biocontrol of Botrytis cinerea, the causal agent of grey mould in grapevines.

A new and sensitive chromogenic assay has been developed to characterize peroxidative activities in plant tissues, applicable to kinetic, zymographic and cytochemical studies on plant peroxidases. This technique is based on the H,O,-dependent oxidation of 4-methoxy-a-naphthol (4-MN) to yield a non-diffusable deep-blue product, the appearance of which is kinetically correlated with the disappearance of 4-MN. Oxidation conditions have been optimized. Since 4-MN is a specific substrate for peroxidase against other heme proteins (catalase and cytochrome c) and, because of the high sensitivity and low detection limit of peroxidase activity in the 4-MN assay, this compound is a powerful reagent in the study of peroxidase activity from plant tissues. The assay has been applied to the kinetic, zymographic and cytochemical characterization of peroxidase activity in grape cell cultures.

No abstract