REGULATION OF POLLEN TUBE GROWTH
In flowering plants, male gametes are delivered to the embryo sac by the pollen tube. The pollen tube develops from a pollen grain after it lands on a compatible stigma and grows rapidly from the stigmatic surface through the style and into the ovary. Growth of the pollen tube is focused at the tip, and Szumlanski and Nielsen (pages 526–544) show that the Rab GTPase RabA4d plays an important role in the regulation of this growth process. The cover image shows in vitro- germinated raba4d mutant pollen grains in the quartet background. Half of the pollen grains express EYFP-RabA4d.