Abstract
In Brassicaceae, a compatible pollen grain adheres to and hydrates on a papilla cell of the stigma. The hydrated pollen grain germinates, and the pollen tube penetrates into the papilla cell wall to deliver the sperm cells to the embryo sac for fertilization. When a pollen grain hydrates and germinates on the papilla cell, water and ions are transported from the papilla cell to the pollen grain. The mechanism of the transport systems, however, is unknown. In this study, we characterized the water transporters, which are essential for pollen hydration. First, pharmacological analysis using an aquaporin inhibitor, HgCl2, suggested that the stigmatic aquaporin(s) are involved in this water transport. Next we identified aquaporins, which are highly expressing in stigmatic papilla cells, by real time PCR and in situ hybridization. We also examined the behaviour of these aquaporins during pollination by expressing their GFP fusions in the papilla cell.
