PtdIns(4,5)P2-dependent plasma membrane recruitment of proteins controlling endocytosis and exocytosis in plants

Endocytosis and exocytosis are key processes in the control of protein trafficking and cell polarity. The membrane lipid PtdIns(4,5)P₂ displays polarized distribution in plant membranes and controls both endocytosis and exocytosis. Therefore, PtdIns(4,5)P₂ likely represents an important regulatory factor for the distribution of proteins in plant cells. Nonetheless, the exact molecular targets of PtdIns(4,5)P₂ in plants are not known to date. A number of hypotheses contended to explain the effects of PtdIns(4,5)P₂ draw immediate analogies to mammalian systems or yeast. However, there are clear differences between phosphoinositide metabolism in these systems and in plants, and in particular plant PI4P 5-kinases contain plant-specific protein domains. In order to move beyond mere speculation and to provide a solid basis for the study of PtdIns(4,5)P₂-effects on endocytosis and exocytosis in plants, we propose to systematically test the regulatory influence of PtdIns(4,5)P₂ on a selection of known elements of the endocytotic and exocytotic machineries. Experiments in this project are designed to elucidate the influence of PtdIns(4,5)P₂ on key players in plant endocytosis and exocytosis, and in vesicle-to-membrane targeting and fusion.