Ion&water transporters during pollen activation&tube growth

Pollen grains, the male gametophytes, are carrying the genetic information to the egg cell of flowering plants. Understanding of the basic cellular and molecular processes that regulate the germination and the growth of pollen tubes, are therefore an important progress in plant reproduction biology, especially for plant breeding. In this project membrane-related processes involved in rehydration, germination, and tube growth were investigated. Liliy pollen tubes represent a good model system for studying polar growth, so-called tip growth, of plants and fungi. The tip growth is driven by an osmotically coupled transport of water and ions and the identification and regulation of transport proteins in the plasma membrane was a major task of this project: 1. a H+ ATPase pumping protons ou of the cell, 2. K+ channels being responsible for K+ influx, and 3. aquaporins facilitating the water uptake. In lily pollen all three transporters were identified and characterized using electrophsiological, biochemical, and /or molecular biology methods. A central role during pollen germination was found for the PM H + ATPase of pollen grains: its activity initiates an uptake of K+ and water, and its activity is regulated by cytoplasmic factors including phosphorylation and 14-3-3. Finally, a combination of the patch-clamp method with single-cell RT-PCR allowed the monitoring of activity and expression level of the PM H+ ATPase in the same, individual pollen grain. This method was successfully established for the first time in plant cells.