title: Microtubule depolymerization affects endocytosis and exocytosis in the tip and influences endosome movement in tobacco pollen tubes.
abstract: Polarized organization of the cytoplasm of growing pollen tubes is maintained by coordinated function of actin filaments (AFs) and microtubules (MTs). AFs convey post-Golgi secretory vesicles to the tip where some fuse with specific domains of the plasma membrane (PM). Secretory activity is balanced by PM retrieval that maintains cell membrane economy and regulates the polarized composition of the PM, by dividing lipids/proteins between the shank and the tip. Although AFs play a key role in PM internalization in the shank, the role of MTs in exo-endocytosis needs to be characterized. The present results show that integrity of the MT cytoskeleton is necessary to control exo-endocytosis events in the tip. MT polymerization plays a role in promoting PM invagination in the apex of tobacco pollen tubes since nocodazole affected PM internalization in the tip and subsequent migration of endocytic vesicles from the apex for degradation. MT depolymerization in the apex and shank was associated with misallocation of a significantly greater amount of internalized PM to the Golgi apparatus and its early recycling to the secretory pathway. Fluorescence Recovery After Photobleaching (FRAP) experiments also showed that MT depolymerization in the tip region influenced the rate of exocytosis in the central domain of the apical PM.
authors.affiliation: Department of Biosciences, Milan University, Via Celoria 26, 20133 Milan, Italy.
authors.forename: Aurora Irene
authors.initials: AI
authors.lastname: Idilli
authors.forename: Piero
authors.initials: P
authors.lastname: Morandini
authors.forename: Elisabetta
authors.initials: E
authors.lastname: Onelli
authors.forename: Simona
authors.initials: S
authors.lastname: Rodighiero
authors.forename: Marco
authors.initials: M
authors.lastname: Caccianiga
authors.forename: Alessandra
authors.initials: A
authors.lastname: Moscatelli
mesh_terms: D001692:Biological Transport / Q000187:drug effects; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D004705:Endocytosis / Q000187:drug effects; D011992:Endosomes / Q000187:drug effects / Q000378:metabolism*; D005089:Exocytosis; D006046:Gold / Q000737:chemistry / Q000378:metabolism; D006056:Golgi Apparatus / Q000187:drug effects / Q000378:metabolism; D053768:Metal Nanoparticles; D008870:Microtubules / Q000187:drug effects / Q000378:metabolism*; D015739:Nocodazole / Q000494:pharmacology; D053205:Pollen Tube / Q000033:anatomy & histology / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D058105:Polymerization / Q000187:drug effects; D014026:Nicotiana / Q000166:cytology*; D014617:Vacuoles / Q000187:drug effects / Q000378:metabolism
chemical_list: D006046:Gold; D015739:Nocodazole
keywords: endocytosis; exocytosis.; microtubules; pollen tube