Abstract
Pollen tube growth is based on transport of secretory vesicles into the apical region where they fuse with a small area of the plasma membrane. The amount of secretion greatly exceeds the quantity of membrane required for growth. Mechanisms of membrane retrieval have recently been demonstrated and partially characterized using FM (Fei Mao) dyes or charged nanogold. Both these probes reveal that clathrin-dependent and -independent endocytosis occur in pollen tubes and are involved in distinct degradation pathways and membrane recycling. Exocytosis, internalization and sorting of PM proteins/lipids depend on the integrity of the actin cytoskeleton and are involved in actin filament organization. However, some kinds of endocytic and exocytic processes occurring in the central area of the tip still need to be characterized. Analysis of secretion dynamics and data derived from endocytosis highlight the complexity of events occurring in the tip region and suggest a new model of pollen tube growth.
Highlights
Pollen tubes are cell protrusions arising from pollen grains
Pollen tubes follow a polarized growth model: their organelles are not uniformly distributed and vesicles accumulate in the apical region or clear zone (5–10 μM from the tip) forming an inverted cone-shaped domain
Improved fixation methods [12] and studies of actin filament (AF) dynamics showing that AF behavior changes cyclically, in line with secretion and growth [13,14,15], and new insights derived from studies of membrane trafficking suggest complex composition and trafficking of vesicles in the apex and in subapical regions
Summary
Pollen tubes are cell protrusions arising from pollen grains. They play a role in transporting and releasing sperm cells in the embryo sac for double fertilization. Improved fixation methods [12] and studies of AF dynamics showing that AF behavior changes cyclically, in line with secretion and growth [13,14,15], and new insights derived from studies of membrane trafficking suggest complex composition and trafficking of vesicles in the apex and in subapical regions These new data are discussed in order to contribute to an integrated tip-growth model. Endocytic vesicles are the smallest vesicles in pollen tubes and have a role in retrieving and recycling excess secreted plasma membrane [11,20], regulating internal membrane economy [18,21] This new data has contributed significantly to formulation of a new model of pollen tube growth
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
