title: Plant-specific microtubule-associated protein SPIRAL2 is required for anisotropic growth in Arabidopsis.
abstract: In diffusely growing plant cells, cortical microtubules play an important role in regulating the direction of cell expansion. Arabidopsis (Arabidopsis thaliana) spiral2 (spr2) mutant is defective in directional cell elongation and exhibits right-handed helical growth in longitudinally expanding organs such as root, hypocotyl, stem, petiole, and petal. The growth of spr2 roots is more sensitive to microtubule-interacting drugs than is wild-type root growth. The SPR2 gene encodes a plant-specific 94-kD protein containing HEAT-repeat motifs that are implicated in protein-protein interaction. When expressed constitutively, SPR2-green fluorescent protein fusion protein complemented the spr2 mutant phenotype and was localized to cortical microtubules as well as other mitotic microtubule arrays in transgenic plants. Recombinant SPR2 protein directly bound to taxol-stabilized microtubules in vitro. Furthermore, SPR2-specific antibody and mass spectrometry identified a tobacco (Nicotiana tabacum) SPR2 homolog in highly purified microtubule-associated protein fractions from tobacco BY-2 cell cultures. These results suggest that SPR2 is a novel microtubule-associated protein and is required for proper microtubule function involved in anisotropic growth.
authors.affiliation: Graduate School of Biological Sciences, Nara Institute of Science and Technology, Ikoma 630-0192, Japan.
authors.forename: Tsubasa
authors.initials: T
authors.lastname: Shoji
authors.forename: Noriyuki N
authors.initials: NN
authors.lastname: Narita
authors.forename: Kazunori
authors.initials: K
authors.lastname: Hayashi
authors.forename: Kazuyuki
authors.initials: K
authors.lastname: Hayashi
authors.forename: Junko
authors.initials: J
authors.lastname: Asada
authors.forename: Takahiro
authors.initials: T
authors.lastname: Hamada
authors.forename: Seiji
authors.initials: S
authors.lastname: Sonobe
authors.forename: Keiji
authors.initials: K
authors.lastname: Nakajima
authors.forename: Takashi
authors.initials: T
authors.lastname: Hashimoto
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D002874:Chromosome Mapping; D018506:Gene Expression Regulation, Plant; D008869:Microtubule-Associated Proteins / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D008870:Microtubules / Q000235:genetics / Q000378:metabolism / Q000648:ultrastructure; D008969:Molecular Sequence Data; D010641:Phenotype; D011485:Protein Binding; D036226:Seedlings / Q000235:genetics / Q000254:growth & development / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D008869:Microtubule-Associated Proteins; C496076:SPIRAL2 protein, Arabidopsis