Arabidopsis SKU6/SPIRAL1 gene encodes a plus end-localized microtubule-interacting protein involved in directional cell expansion

• Published in: The Plant cell 2004-06, Vol.16 (6), p.1506-1520
• Main Authors: Sedbrook, J.C, Ehrhardt, D.W, Fisher, S.E, Scheible, W.R, Somerville, C.R
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; amino acid sequences; Arabidopsis - cytology; Arabidopsis - drug effects; Arabidopsis - genetics; Arabidopsis - metabolism; Arabidopsis Proteins - chemistry; Arabidopsis Proteins - genetics; Arabidopsis Proteins - metabolism; Arabidopsis thaliana; Benzamides - pharmacology; binding proteins; Cell growth; Cell Size; Cloning; Cloning, Molecular; cortical microtubules; Dinitrobenzenes - pharmacology; Epidermal cells; exons; Genes, Plant - genetics; Genetic mutation; hypocotyls; introns; microtubule polymerization; Microtubule Proteins - chemistry; Microtubule Proteins - genetics; Microtubule Proteins - metabolism; Microtubule-Associated Proteins - chemistry; Microtubule-Associated Proteins - genetics; Microtubule-Associated Proteins - metabolism; Microtubules; Microtubules - drug effects; Microtubules - metabolism; Molecular Sequence Data; multigene family; Multigene Family - genetics; mutants; Mutation - genetics; nucleotide sequences; Phenotype; Plant cells; Plant growth; plant morphology; plant proteins; Plant roots; Plant Roots - genetics; Plant Roots - growth & development; Plants; Plants, Genetically Modified; Polymers; Protein Binding; Proteins; RNA, Messenger - genetics; RNA, Messenger - metabolism; Root tips; roots; Rotation; Seedlings; Seedlings - genetics; Seedlings - growth & development; SPR1 gene; SPR1-6 gene; structural genes; Sulfanilamides
• ISSN: 1040-4651; 1532-298X; 1532-298X
• DOI: 10.1105/tpc.020644

The sku6-1 mutant of Arabidopsis thaliana exhibits altered patterns of root and organ growth. sku6 roots, etiolated hypocotyls, and leaf petioles exhibit right-handed axial twisting, and root growth on inclined agar media is strongly right skewed. The touch-dependent sku6 root skewing phenotype is suppressed by the antimicrotubule drugs propyzamide and oryzalin, and right skewing is exacerbated by cold treatment. Cloning revealed that sku6-1 is allelic to spiral1-1 (spr1-1). However, modifiers in the Columbia (Col) and Landsberg erecta (Ler) ecotype backgrounds mask noncomplementation in sku6-1 (Col)/spr1-1 (Ler) F1 plants. The SPR1 gene encodes a plant-specific 12-kD protein that is ubiquitously expressed and belongs to a six-member gene family in Arabidopsis. An SPR1:green fluorescent protein (GFP) fusion expressed in transgenic seedlings localized to microtubules within the cortical array, preprophase band, phragmoplast, and mitotic spindle. SPR1:GFP was concentrated at the growing ends of cortical microtubules and was dependent on polymer growth state; the microtubule-related fluorescence dissipated upon polymer shortening. The protein has a repeated motif at both ends, separated by a predicted rod-like domain, suggesting that it may act as an intermolecular linker. These observations suggest that SPR1 is involved in microtubule polymerization dynamics and/or guidance, which in turn influences touch-induced directional cell expansion and axial twisting.