title: Arabidopsis villins promote actin turnover at pollen tube tips and facilitate the construction of actin collars.
abstract: Apical actin filaments are crucial for pollen tube tip growth. However, the specific dynamic changes and regulatory mechanisms associated with actin filaments in the apical region remain largely unknown. Here, we have investigated the quantitative dynamic parameters that underlie actin filament growth and disappearance in the apical regions of pollen tubes and identified villin as the major player that drives rapid turnover of actin filaments in this region. Downregulation of Arabidopsis thaliana VILLIN2 (VLN2) and VLN5 led to accumulation of actin filaments at the pollen tube apex. Careful analysis of single filament dynamics showed that the severing frequency significantly decreased, and the lifetime significantly increased in vln2 vln5 pollen tubes. These results indicate that villin-mediated severing is critical for turnover and departure of actin filaments originating in the apical region. Consequently, the construction of actin collars was affected in vln2 vln5 pollen tubes. In addition to the decrease in severing frequency, actin filaments also became wavy and buckled in the apical cytoplasm of vln2 vln5 pollen tubes. These results suggest that villin confers rigidity upon actin filaments. Furthermore, an observed decrease in skewness of actin filaments in the subapical region of vln2 vln5 pollen tubes suggests that villin-mediated bundling activity may also play a role in the construction of actin collars. Thus, our data suggest that villins promote actin turnover at pollen tube tips and facilitate the construction of actin collars.
authors.affiliation: Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China.
authors.forename: Xiaolu
authors.initials: X
authors.lastname: Qu
authors.forename: Hua
authors.initials: H
authors.lastname: Zhang
authors.forename: Yurong
authors.initials: Y
authors.lastname: Xie
authors.forename: Juan
authors.initials: J
authors.lastname: Wang
authors.forename: Naizhi
authors.initials: N
authors.lastname: Chen
authors.forename: Shanjin
authors.initials: S
authors.lastname: Huang
mesh_terms: D008841:Actin Cytoskeleton / Q000235:genetics / Q000378:metabolism; D000199:Actins / Q000235:genetics / Q000378:metabolism*; D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D008840:Microfilament Proteins / Q000235:genetics / Q000378:metabolism*; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D008954:Models, Biological; D009154:Mutation; D030821:Plants, Genetically Modified; D053205:Pollen Tube / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D022161:Transport Vesicles / Q000378:metabolism; D020691:rab GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D000199:Actins; D029681:Arabidopsis Proteins; D008164:Luminescent Proteins; D008840:Microfilament Proteins; C026615:villin; C585920:villin 2 protein, Arabidopsis; D020691:rab GTP-Binding Proteins