THE SUBCELLULAR-LOCALIZATION OF ISOPEROXIDASES IN CAPSICUM-ANNUUM LEAVES AND THEIR DIFFERENT EXPRESSION IN VEGETATIVE AND FLOWERED PLANTS

The subcellular localization of leaf peroxidases (EC 1.11.1.7) and their expression in vegetative and flowered plants has been studied in Capsicum annuum (var. annuum) in order to assess whether the expression of new peroxidase isoenzymes can characterize the floral state which determines the beginning of reproductive development. The results showed that floral development is accompanied by a significant increase in the level of soluble (non-sedimentable) leaf peroxidase, independently of leaf position along the internodes, and therefore independently of the leaf age. An analysis of the leaf peroxidase isoenzyme patterns along the internodes for vegetative and flowered plants shows that the increase in peroxidase activity is due to a general increase in the activity of all the pre-existing peroxidase isoenzymes, although isoenzyme Bä and, especially, isoenzyme A1 showed a distinctive and major increase in activity. These two isoenzymes are mainly ionically-bound to cell walls, probably in equilibrium with the same isoenzymes moving freely in the cell-wall free spaces. This differs from other peroxidase isoenzymes, such as isoperoxidase B6, which is mainly located in the covalently-bound cell-wall fraction and in mesophyll vacuoles. These results are discussed in the light of a possible role of cell wall peroxidases as markers of the floral state in Capsicum annuum morphogenesis. © 1993 Annals of Botany Company.