Subcellular localization of peroxidase in tomato fruit skin and the possible implications for the regulation of fruit growth

• Published in: Journal of experimental botany 2002-11, Vol.53 (378), p.2185-2191
• Main Authors: Andrews, J., Adams, S. R., Burton, K. S., Evered, C. E.
• Format: Article
• Language: English
• Subjects: Agronomy. Soil science and plant productions; Animal cuticle; Biological and medical sciences; Cell membranes; Cell Wall - enzymology; Cell walls; Economic plant physiology; Enzymes; Exocarp; Fruit - enzymology; Fruit - growth & development; Fruit - ultrastructure; Fruits; Fundamental and applied biological sciences. Psychology; Histocytochemistry; Isoelectric Focusing; Isoenzymes - metabolism; Key words: Fruit growth; Lignin - analogs & derivatives; Lignin - metabolism; localization; Lycopersicon esculentum; Lycopersicon esculentum - enzymology; Lycopersicon esculentum - growth & development; Metabolism; Microscopy, Electron; Microscopy, Fluorescence; Nutrition. Photosynthesis. Respiration. Metabolism; peroxidase; Peroxidase - metabolism; Phenols - metabolism; Plant cuticle; Plant Epidermis - cytology; Plant Epidermis - enzymology; Plant Epidermis - ultrastructure; Plant physiology and development; Plants; Regulation of Growth, Development and Whole Organism Physiology; Skin; tomato; Tonoplast; Vacuoles
• ISSN: 0022-0957; 1460-2431; 1460-2431
• DOI: 10.1093/jxb/erf070

The cessation of tomato fruit growth has been associated with the appearance of three ‘wall‐bound’ peroxidase isozymes in the skin of tomato fruit. However, the presence of these isozymes in the ionically eluted ‘wall‐bound’ fraction may be an artefact of either non‐specific binding of symplastic peroxidase to the cell wall, or isozymes bound to membranes included in the ‘wall‐bound’ fraction. Therefore, subcellular localization of peroxidase in both immature and mature tomato fruit skins was studied. Immature fruits showed intense peroxidase activity associated with the tonoplast and pro‐vacuolar membranes, but little or no activity associated with the cell wall. However, the presence of peroxidase activity within the cell wall of mature green fruits was confirmed. Furthermore, peroxidase activity was also observed associated with the plasma membrane and large vesicles allied to the plasma membrane. While cross‐linking in cell wall components was previously assumed to be the mechanism by which peroxidase might control fruit growth, the incorporation of ‘lignin‐like’ phenolics may also play a part. Isoelectric focusing (IEF) of both symplastic and apoplastic peroxidase extracted from immature and mature tomato fruit skin showed that all peroxidase isozymes present were highly anionic. In this current study, histochemical techniques are used to demonstrate a developmental increase in ‘lignin‐like’ phenolics within the sub‐cuticular cell walls of the fruit skin. The localization of peroxidase within tomato fruit skin is discussed in relation to its potential role in the regulation of tomato fruit growth.