Calcium signalling in pollen of Papaver rhoeas undergoing the self-incompatibility (SI) response

Self-incompatibility (SI) is a genetically controlled system used by many f lowering plants to prevent self-pollination. We established, using calcium imaging, that the SI response in Papaver rhoeas L. (poppy) pollen involves a Ca2+-mediated intracellular signalling pathway. Here we review what is kn own about the signalling components and cascades implicated in the SI respo nse in poppy pollen. We present some studies using calcium green (CG-1) tha t show SI-induced alterations in CG-1 fluorescence and localization. We hav e begun to examine potential sources of Ca2+ involved in the responses indu ced by SI. This work presents preliminary data showing that influx of extra cellular Ca2+ at the "shank" of the pollen tube is possible. This is the fi rst evidence suggesting that influx at this localization may play a role in the SI response. We also describe preliminary studies that begin to invest igate whether the phosphoinositide signalling pathway is implicated in the SI response.