Helical growth of the Arabidopsis mutant tortifolia1 reveals a plant-specific microtubule-associated protein.
Plants can grow straight or in the twisted fashion exhibited by the helical growth of some climbing plants. Analysis of helical-growth mutants from Arabidopsis has indicated that microtubules are involved in the expression of the helical phenotype. Arabidopsis mutants growing with a right-handed twist have been reported to have cortical microtubules that wind around the cell in left-handed helices and vice versa. Microtubular involvement is further suspected from the finding that some helical mutants are caused by single amino acid substitutions in alpha-tubulin and because of the sensitivity of the growth pattern to anti-microtubule drugs. Insight into the roles of microtubules in organ elongation is anticipated from analyses of genes defined by helical mutations. We investigated the helical growth of the Arabidopsis mutant tortifolia1/spiral2 (tor1/spr2), which twists in a right-handed manner, and found that this correlates with a complex reorientation of cortical microtubules. TOR1 was identified by a map-based approach; analysis of the TOR1 protein showed that it is a member of a novel family of plant-specific proteins containing N-terminal HEAT repeats. Recombinant TOR1 colocalizes with cortical microtubules in planta and binds directly to microtubules in vitro. This shows that TOR1 is a novel, plant-specific microtubule-associated protein (MAP) that regulates the orientation of cortical microtubules and the direction of organ growth.
Institute of Biochemical Plant Pathology, GSF--National Research Center for Environment and Health, D-85764 Neuherberg, Germany.
Henrik
H
Buschmann
Christoph O
CO
Fabri
Monika
M
Hauptmann
Peter
P
Hutzler
Thomas
T
Laux
Clive W
CW
Lloyd
Anton R
AR
Schäffner
D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics* / Q000254:growth & development*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D015152:Blotting, Northern; D002874:Chromosome Mapping; D017931:DNA Primers; D018076:DNA, Complementary / Q000235:genetics; D049452:Green Fluorescent Proteins; D007150:Immunohistochemistry; D008164:Luminescent Proteins / Q000378:metabolism; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism*; D008870:Microtubules / Q000378:metabolism / Q000502:physiology*; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D021141:Nucleic Acid Amplification Techniques; D010641:Phenotype; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D014170:Transformation, Genetic
D029681:Arabidopsis Proteins; D017931:DNA Primers; D018076:DNA, Complementary; D008164:Luminescent Proteins; D008869:Microtubule-Associated Proteins; D049452:Green Fluorescent Proteins