The long term goal of this research is to understand the cell signaling that occurs between Arabidopsis pollen (and/or pollen tubes) and the pistil. This proposal initiates an investigation of the molecules essential for pollen-stigma communication. Previous analyses of male- sterile cer6-2 Arabidopsis plants showed they produce pollen lacking a normal extracellular coating. While this coating is essential for communication with the stigma, it is not clear which of its components (lipids, proteins, small molecules) play a critical role in communication. This proposal is aimed at characterizing further the signaling component(s). These experiments rely on recently developed methods for obtaining large quantities of pollen and for extracting the pollen coating. When the extracted wild type pollen coat is dried and added to the cer6-2 pollen, it restores fertility, providing a bioassay; this bioassay will allow initial purification of the active pollen coat components. Specifically, the coating from wild type grains will be fractionated and each fraction will be added separately to the mutant cer6-2 pollen. Restoration of fertility will identify the active fraction(s). Recent experiments have shown that the Arabidopsis pollen coating contains only a few proteins. One or more of these proteins may play a significant role i interaction with the stigma, including adhesion of pollen to the stigmatic cells or communication with the stigma. The fractions prepared for the bioassay experiments will also be used to characterize the protein components.
