Spatial and temporal induction of H +-ATPase during flower development in Pisum sativum L.

Abstract

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 flowers. A high level of H +-ATPase, restricted to the core of the L3 layer, was observed in early floral meristems. Later, a strong and transient induction of the enzyme was chronologically detected in anthers and in non-differentiated parenchyma cells from sepals. Temporal gradients 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 gibberellic acid. During their early stages of development, petals showed no detectable H +-ATPase and, indeed, its production was restricted mainly to differentiated tissues of vascular bundles, as observed in other fully differentiated organs of mature flowers. Parenchyma cells from both immature stipules and young leaves, also showed a high level of H +-ATPase 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 expression supporting the view that, in tissues other than those specialized for transport, the enzyme may also be implicated temporally in processes of ion and nutrient uptake during cellular growth and differentiation.