Recommend Plant Signaling & Behavior (PS&B) to your librarian for 2008. Download form here.

Sign up for Table of Contents Alerts!

PS&B is the official journal of the Society for Plant Neurobiology. Full membership ($60 annually) and student membership ($30 annually) include online access to the journal. Click here to join.

Email this page

Print this page

Article Addendum

Regulation of pollen tube polarity: Feedback loops rule

Yan Zhang and Sheila McCormick

Purchase article for $19

Subscribe to this journal for $79/year

Targeted delivery of immotile sperm through growing pollen tubes is a crucial step in achieving sexual reproduction in angiosperms. Unlike diffuse-growing cells, the growth of a pollen tube is restricted to the very apical region where targeted exocytosis and regulated endocytosis occur. The plant-specific Rho GTPases, Rops, are central organizers for pollen tube polarity. Through effector binding, Rops regulate the tip-focused Ca²⁺ gradient and the actin cytoskeleton during pollen tube growth. Therefore, understanding the spatiotemporal regulation of Rop activity would reveal how establishment and maintenance of tube polarity as well as re-orientation of the growth axis are accomplished. Recent findings indicated that two feedback loops may be fundamental in maintaining a fine-tuned and dynamic Rop activity. The concerted activities of RopGAP and RopGDI prevent lateral diffusion of activated Rop, restricting Rop activity to the apical plasma membrane. Conversely, pollen receptor kinases (PRKs) and RopGEFs positively feedback regulate Rop activity through protein binding and membrane recruitment. Feedback loops would also be essential for pollen tube re-orientation. Shallow extracellular cues amplified by concerted activities of feedback loops would lead to asymmetric activation of Rop and result in tube re-orientation.

Authors

Yan Zhang

Plant Gene Expression Center; United States Department of Agriculture/Agricultural Research Service; and Department of Plant and Microbial Biology; University of California at Berkeley; Albany, California USA

Sheila McCormick

Plant Gene Expression Center; United States Department of Agriculture/Agricultural Research Service; and Department of Plant and Microbial Biology; University of California at Berkeley; Albany, California USA

Purchase article for $19

Subscribe to this journal for $79/year