Myrosin Cells and Myrosinase Expression Pattern in Nasturtium (Tropaeolum majus L.)

Plants from the Brassicales order are known for the presence of a glucosinolate–myrosinase link, which is an important protection strategy against multiple stressors. The main goal of this study was to investigate the presence of the myrosinase enzyme and reveal the myrosin cell ultrastructure in the vegetative organs of nasturtium. The presence, localisation and expression of the enzyme myrosinase type 1 (TGG1) at different developmental stages of Tropaeolum majus L. (nasturtium) were investigated using immunohistochemical and immunofluorescent techniques. The expression of myrosinase was detected in the vegetative organs of T. majus. During plant development, within four consecutive weeks, a decrease in myrosinase expression was noticed in all studied plant organs. The location of greater myrosinase accumulation and activity is shown to be the root, contrary to the nasturtium stem and leaf, where we found the lowest myrosinase expression. Transmission electron microscopy was used to reveal the ultrastructural features of the myrosin cells of nasturtium. Myrosin cells are usually scattered between parenchyma cells and S-cells. Mostly, they are rectangular or slightly elongated in shape and can be recognised by an electron-dense large central vacuole and an expanded rough endoplasmic reticulum. The results of this study provide new data on myrosin cell morphology and the expression pattern of myrosinase in T. majus.