title: Augmin plays a critical role in organizing the spindle and phragmoplast microtubule arrays in Arabidopsis.
abstract: In higher plant cells, microtubules (MTs) are nucleated and organized in a centrosome-independent manner. It is unclear whether augmin-dependent mechanisms underlie spindle MT organization in plant cells as they do in animal cells. When AUGMIN subunit3 (AUG3), which encodes a homolog of animal dim γ-tubulin 3/human augmin-like complex, subunit 3, was disrupted in Arabidopsis thaliana, gametogenesis frequently failed due to defects in cell division. Compared with the control microspores, which formed bipolar spindles at the cell periphery, the mutant cells often formed peripheral half spindles that only attached to condensed chromosomes or formed elongated spindles with unfocused interior poles. In addition, defective cells exhibited disorganized phragmoplast MT arrays, which caused aborted cytokinesis. The resulting pollen grains were either shrunken or contained two nuclei in an undivided cytoplasm. AUG3 was localized along MTs in the spindle and phragmoplast, and its signal was pronounced in anaphase spindle poles. An AUG3-green fluorescent protein fusion exhibited a dynamic distribution pattern, similar to that of the γ-tubulin complex protein2. When AUG3 was enriched from seedlings by affinity chromatography, AUG1 was detected by immunoblotting, suggesting an augmin-like complex was present in vivo. We conclude that augmin plays a critical role in MT organization during plant cell division.
authors.affiliation: Department of Plant Biology, University of California, Davis, California 95616, USA.
authors.forename: Chin-Min Kimmy
authors.initials: CM
authors.lastname: Ho
authors.forename: Takashi
authors.initials: T
authors.lastname: Hotta
authors.forename: Zhaosheng
authors.initials: Z
authors.lastname: Kong
authors.forename: Cui Jing Tracy
authors.initials: CJ
authors.lastname: Zeng
authors.forename: Jie
authors.initials: J
authors.lastname: Sun
authors.forename: Yuh-Ru Julie
authors.initials: YR
authors.lastname: Lee
authors.forename: Bo
authors.initials: B
authors.lastname: Liu
mesh_terms: D000818:Animals; D017360:Arabidopsis / Q000166:cytology* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism; D005816:Genetic Complementation Test; D006801:Humans; D018519:Meristem / Q000166:cytology / Q000502:physiology; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism*; D008870:Microtubules / Q000378:metabolism*; D008938:Mitosis / Q000502:physiology; D046912:Multiprotein Complexes / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D056771:Ovule / Q000166:cytology / Q000502:physiology; D018517:Plant Roots / Q000033:anatomy & histology / Q000502:physiology; D011058:Pollen / Q000166:cytology / Q000502:physiology; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D008941:Spindle Apparatus / Q000378:metabolism* / Q000473:pathology / Q000648:ultrastructure; D014404:Tubulin / Q000378:metabolism
chemical_list: C570177:AUG3 protein, Arabidopsis; D029681:Arabidopsis Proteins; D018797:Cell Cycle Proteins; D008869:Microtubule-Associated Proteins; D046912:Multiprotein Complexes; D011993:Recombinant Fusion Proteins; D014404:Tubulin