Investigating the targets and mechanisms regulating self incompatibility in papaver rhoeas pollen

Many higher plants use self-incompatibil ity (SI) mechanism to prevent inbreeding and thus encouraging outcrossing. Upon a self-challenge in Papaver rhoeas, a Ca2+-dependent-signal ling-cascade is initiated resulting in the destruction ofthe self-pollen by Programmed Cell Death. Upstream ofPCD, several Sl-specific events are triggered in incompatible pollen, including phosphorylation of soluble inorganic pyrophosphatases (sPPases); alterations to actin; increases in Reactive Oxygen Species (ROS) and Nitric Oxide (NO). In Papaver pollen, sPPases play an important role, as they provide the driving force for biosynthesis; data suggested that Ca2+ and phosphorylation inhibits the sPPases activities, contributing to pollen tube inhibition. Work presented in this thesis characterized Pr-p26.1 sPPases and analysis of phosphomimic mutants in the SI signalling. These studies provide good evidence that, together with Ca2+, phosphorylation, H20 2 and pH dramatically affect sPPase activity. As previous studies showed that increases in ROS and NO are triggered by Sl in incompatible pollen, to provide insights into SI-mediated events, this project investigated protein-targets in pollen modified by oxidation and Snitrosylations after Sl, including actin and actin-associated proteins. Using a mass spectrometry approach we identified several proteins that were modified by oxidation and S-nitrosylation. This has provided us with several potential new mechanisms involved in Sl