title: The {gamma}-tubulin complex protein GCP4 is required for organizing functional microtubule arrays in Arabidopsis thaliana.
abstract: Microtubule (MT) nucleation and organization depend on the evolutionarily conserved protein gamma -tubulin, which forms a complex with GCP2-GCP6 (GCP for gamma -Tubulin Complex Protein). To date, it is still unclear how GCP4-GCP6 (the non-core GCPs) may be involved in acentrosomal MT nucleation in plant cells. We found that GCP4 was associated with gamma -tubulin in vivo in Arabidopsis thaliana. When GCP4 expression was repressed by an artificial microRNA, transgenic plants exhibited phenotypes of dwarfism and reduced organ size. In mitotic cells, it was observed that the gamma -tubulin signal associated with the mitotic spindle, and the phragmoplast was depleted when GCP4 was downregulated. Consequently, MTs failed to converge at unified spindle poles, and the bipolar phragmoplast MT array frequently had discrete bundles with extended minus ends, resulting in failed cytokinesis as reflected by cell wall stubs in leaf epidermal cells. In addition, cortical MTs in swollen guard cells and pavement cells of the leaf epidermis became hyperparallel and bundled, which was likely caused by frequent MT nucleation with shallow angles on the wall of extant MTs. Therefore, our results support the notion that GCP4 is an indispensable component for the function of gamma -tubulin in MT nucleation and organization in plant cells.
authors.affiliation: Department of Plant Biology, University of California, Davis, California 95616, USA.
authors.forename: Zhaosheng
authors.initials: Z
authors.lastname: Kong
authors.forename: Takashi
authors.initials: T
authors.lastname: Hotta
authors.forename: Yuh-Ru Julie
authors.initials: YR
authors.lastname: Lee
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Horio
authors.forename: Bo
authors.initials: B
authors.lastname: Liu
mesh_terms: D017360:Arabidopsis / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D048749:Cytokinesis; D035683:MicroRNAs / Q000235:genetics; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism*; D008870:Microtubules / Q000378:metabolism*; D008969:Molecular Sequence Data; D009154:Mutation; D030821:Plants, Genetically Modified / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics; D018749:RNA, Plant / Q000235:genetics; D008941:Spindle Apparatus / Q000378:metabolism; D014404:Tubulin / Q000235:genetics / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; D035683:MicroRNAs; D008869:Microtubule-Associated Proteins; D012333:RNA, Messenger; D018749:RNA, Plant; D014404:Tubulin