Small GTPases and spatiotemporal regulation of pollen tube growth

Abstract

During in vivo growth, pollen tubes make a long journey toward the ovule, responding to long- and short-distance guidance cues and elongating through different female tissues. Thus, pollen tube growth and guidance require complicated inter- and intracellular signaling, integration of multiple signals, and spatiotemporal coordination of the downstream responses necessary for targeted exocytosis. ROP, a plant-unique family of Rho small G proteins, is known to function as a versatile molecular switch in a variety of processes such as cell morphogenesis, stress and defense responses, hormonal responses, and directional growth of pollen tubes and root hairs. Current evidence suggests that ROP GTPase controls pollen tube growth temporally and spatially, coordinating multiple downstream signaling pathways. This chapter will review up-to-date findings about ROP GTPase signaling in pollen tubes and will discuss how ROP regulates pollen tube growth. © Springer-Verlag Berlin Heidelberg 2006.