title: Actin polymerization promotes the reversal of streaming in the apex of pollen tubes.
abstract: Actin polymerization is important in the control of pollen tube growth. Thus, treatment of pollen tubes with low concentrations of latrunculin B (Lat-B), which inhibits actin polymerization, permits streaming but reversibly blocks oscillatory growth. In the current study, we employ Jasplakinolide (Jas), a sponge cyclodepsipeptide that stabilizes actin microfilaments and promotes polymerization. Uniquely, Jas (2 microM) blocks streaming in the shank of the tube, but induces the formation of a toroidal-shaped domain in the swollen apex, of which longitudinal optical sections exhibit circles of motion. The polarity of this rotary motion is identical to that of reverse fountain motility in control pollen tubes, with the forward direction occurring at the edge of the cell and the rearward direction in the cell interior. Support for the idea that actin polymerization in the apical domain contributes to the formation of this rotary motility activity derives from the appearance therein of aggregates and flared cables of F-actin, using immunofluorescence, and by the reduction in G-actin as indicated with fluorescent DNAse. In addition, Jas reduces the tip-focused Ca2+ gradient. However, the alkaline band appears in the swollen apex and is spatially localized with the reverse fountain streaming activity. Taken together, our results support the idea that actin polymerization promotes reversal of streaming in the apex of the lily pollen tube.
authors.affiliation: Biology Department, and the Plant Biology Graduate Program, Morrill Science Center, University of Massachusetts, Amherst, USA. luisc@ibt.unam.mx
authors.forename: Luis
authors.initials: L
authors.lastname: Cárdenas
authors.forename: Alenka
authors.initials: A
authors.lastname: Lovy-Wheeler
authors.forename: Kathleen L
authors.initials: KL
authors.lastname: Wilsen
authors.forename: Peter K
authors.initials: PK
authors.lastname: Hepler
mesh_terms: D008841:Actin Cytoskeleton / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D000199:Actins / Q000187:drug effects / Q000378:metabolism*; D000935:Antifungal Agents / Q000494:pharmacology; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000502:physiology; D002465:Cell Movement / Q000187:drug effects / Q000502:physiology; D016764:Cell Polarity / Q000187:drug effects / Q000502:physiology*; D015638:Cytochalasin D / Q000494:pharmacology; D003593:Cytoplasm / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D003595:Cytoplasmic Streaming / Q000502:physiology*; D003851:Deoxyribonucleases / Q000378:metabolism; D047630:Depsipeptides / Q000494:pharmacology; D035264:Flowers / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D018525:Germination / Q000187:drug effects / Q000502:physiology; D027762:Lilium / Q000378:metabolism* / Q000648:ultrastructure; D019384:Nucleic Acid Synthesis Inhibitors / Q000494:pharmacology; D011058:Pollen / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D011108:Polymers / Q000378:metabolism; D012098:Reproduction / Q000502:physiology; D013844:Thiazoles / Q000494:pharmacology; D053778:Thiazolidines
chemical_list: D000199:Actins; D000935:Antifungal Agents; D019086:Bridged Bicyclo Compounds, Heterocyclic; D047630:Depsipeptides; D019384:Nucleic Acid Synthesis Inhibitors; D011108:Polymers; D013844:Thiazoles; D053778:Thiazolidines; C057531:jasplakinolide; D015638:Cytochalasin D; D003851:Deoxyribonucleases; C037068:latrunculin B; D002118:Calcium