title: Randomization of cortical microtubules in root epidermal cells induces root hair initiation in lettuce (Lactuca sativa L.) seedlings.
abstract: Root hair formation is induced when lettuce seedlings are transferred from liquid medium at pH 6.0 to fresh medium at pH 4.0. If seedlings are transferred to pH 6.0, no root hairs are formed. We investigated the role of microtubules in this low pH-induced root hair initiation in lettuce. At the hair-forming zone in root epidermal cells, microtubules were perpendicular to the longitudinal axis of the cell just after pre-culture. This arrangement became disordered as early as 5 min after transfer to pH 4.0, and became random by 30 min later. At pH 4.0, the randomization extended to the entire hair-forming zone of seedlings; at pH 6.0, however, randomization did not occur and transverse microtubules were maintained. When seedlings at pH 6.0 were treated with microtubule-depolymerizing drugs, root hairs were formed. In contrast, when a microtubule-stabilizing drug, taxol, was added to the medium, no root hairs formed, even at pH 4.0. These results suggest that the transverse cortical microtubules inhibit root hair formation, and that their destruction is necessary for initiation. Furthermore, the microfilament-disrupting drugs cytochalasin B and latrunculin B inhibited root hair initiation, suggesting that actin filaments are necessary for root hair initiation.
authors.affiliation: Department of Applied Biological Sciences, Faculty of Science and Technology, Tokyo University of Science, Yamazaki 2641, Noda, Chiba, 278-8510 Japan. takahide@rs.noda.tus.ac.jp
authors.forename: Hidenori
authors.initials: H
authors.lastname: Takahashi
authors.forename: Kayoko
authors.initials: K
authors.lastname: Hirota
authors.forename: Aiko
authors.initials: A
authors.lastname: Kawahara
authors.forename: Erika
authors.initials: E
authors.lastname: Hayakawa
authors.forename: Yasunori
authors.initials: Y
authors.lastname: Inoue
mesh_terms: D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000494:pharmacology; D003571:Cytochalasin B / Q000494:pharmacology; D004136:Dinitrobenzenes / Q000494:pharmacology; D018545:Lactuca / Q000254:growth & development / Q000378:metabolism*; D008870:Microtubules / Q000187:drug effects / Q000378:metabolism*; D017239:Paclitaxel / Q000494:pharmacology; D019441:Plant Epidermis / Q000254:growth & development / Q000378:metabolism*; D018517:Plant Roots / Q000254:growth & development / Q000378:metabolism*; D013424:Sulfanilamides; D013844:Thiazoles / Q000494:pharmacology; D053778:Thiazolidines
chemical_list: D019086:Bridged Bicyclo Compounds, Heterocyclic; D004136:Dinitrobenzenes; D013424:Sulfanilamides; D013844:Thiazoles; D053778:Thiazolidines; D003571:Cytochalasin B; C012465:oryzalin; C037068:latrunculin B; D017239:Paclitaxel