EFFECTS OF A MECHANICAL STIMULATION ON LOCALIZATION OF ANNEXIN-LIKE PROTEINS IN BRYONIA-DIOICA INTERNODES

Mechanical stimulation exerted by rubbing a young internode of Bryonia dioica plants inhibits its growth. Previous cellular and biochemical studies showed that this growth inhibition is associated with Ca2+ red istribution and profound modifications of plasma membrane characterist ics. We extracted and purified Ca2+-dependent phospholipid-binding pro teins from B. dioica internodes. Two main proteins, p33 and p35, and o ther minor bands were isolated and identified as annexin-like proteins because of their biochemical properties and their cross-reactions wit h antibodies against maize (Zea mays L.) annexins. Rabbit antiserum wa s obtained by injection of B. dioica p35. This antiserum was used for the immunocytolocalization of annexin-like proteins in internode paren chyma cells. It appeared that the distribution of annexin-like protein s was different before and 30 min after the mechanical stimulation. We stern analysis of proteins in membrane fractions after separation by f ree-flow electrophoresis showed that p35 was present in most fractions , whereas p33 appeared mainly in plasmalemma-enriched fractions after the mechanical stimulation. It is hypothesized that a subcellular redi stribution of these proteins might be involved in growth inhibition by mechanical stress.