Localization myrosinase

Arabidopsis thaliana (L.) Heynh. is today the most useful model system in plant research, and in order to be able to generalize results from this species, it is important to investigate its special characteristics, such as the myrosinase-glucosinolate system. In this chapter, we present the localization of the myrosinase-glucosinolate system in Arabidopsis and other plants and discuss in vivo degradation and transport of glucosinolates. 

Staining of consecutive sections with histochemical reagents for protein and antibodies against myrosinase showed that myrosin cells actually contain myrosinase (Fig. 4.2D,E).18,43,44 By electron microscopy immunogold labelling studies, the enzyme was localized to the interior of the vacuoles of the myrosin cells (Fig. 4.2F).18,40,41 It has also been shown by several in situ hybridization experiments that myrosinase transcripts are located in these cells (Fig. 4.2G),6 demonstrating that the cellular localization of myrosinase is due to transcriptional regulation and not to a transport process. No evidence for transport of myrosinase currently exists. These methods for detection and identification of myrosin cells and myrosinase expression are illustrated (Fig. 4.2). For a historical overview of myrosinase localization studies, see Bones and Rossiter.45... 

HOGLUND A.-S., LENMAN, M., RASK, L., Myrosinase is localized to the interior of myrosin grains and is not associated to the surrounding tonoplast membrane., Plant... 

GESHI, N., ANDREASSON, E., MEUER, J., RASK, L., BRANDT, A., Myrosinase and myrosinase-binding proteins are co-localized in grains of myrosin cells in cotyledon of Brassica napus L. seedlings., Plant Physiol. Biochem., 1998,36, 583-590. 

B. brassicae tissue fixed with glutaraldehyde was visualized by light microscopy using silver enhanced immunogold localization and showed the presence of myrosinase over the skeletal muscle of the head, thorax, and abdomen. Labelling was restricted to skeletal muscle, while in all sections examined flight muscles remain free of myrosinase. 

Apart from fhe presence of myrosinase in fhe cytosol, enzyme activity can also be detected in cell walls, corresponding to an apoplastic localization (Matile, 1980). Apoplastic occurrence was confirmed by Hoglund et al (1991), who found myrosinase acfivify in the xylem. 

Andreasson, E. and Jorgenson, L.B. (2003) Localization of plant myrosinases and glucosinolates, in Recent Advances in Phytochemistry Integrative Phytochemistry From Ethnobotany to Molecular Ecology (ed. J.T. Romeo). Pergamon, Oxford, pp. 79-99. 

Thangstad, O.P., Iversen, T.-H., Slupphaug, G. and Bones, A. (1990) Immunocyto-chemical localization of myrosinase in Brassica napus (L.). Planta, 180, 245-8. 

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