SPATIAL AND TEMPORAL INDUCTION OF H-ATPASE DURING FLOWER DEVELOPMENT IN PISUM-SATIVUM L()

The distribution of plasma membrane H+-ATPase has been analyzed during pea (Pisum sativum L.) flower development using a specific polyclonal antibody, generated against the carboxyl terminal domain of a plasma- membrane H+-ATPase from Arabidopsis thaliana on paraffin sections of f lowers. A high level of H+-ATPase, restricted to the core of the L3 la yer, was observed in early floral meristems. Later, a strong and trans ient induction of the enzyme was chronologically detected in anthers a nd in non-differentiated parenchyma cells from sepals. Temporal gradie nts of H+-ATPase expression were observed within the mesocarp layer of the ovary. The pattern of H+-ATPase expression was independent of the pollination of the pea ovary or its induced development by gibberelli c acid. During their early stages of development, petals showed no det ectable H+-ATPase and, indeed, its production was restricted mainly to differentiated tissues of vascular bundles, as observed in other full y differentiated organs of mature flowers. Parenchyma cells from both immature stipules and young leaves, also showed a high level of H+-ATP ase expression during early stages of organ development. Although the existence of a basal expression of H+-ATPase in all plant cells cannot be excluded, the enzyme displayed a fine regulated pattern of express ion supporting the view that, in tissues other than those specialized for transport, the enzyme may also be implicated temporally in process es of ion and nutrient uptake during cellular growth and differentiati on.