title: Cellular basis for the automorphic curvature of rice coleoptiles on a three-dimensional clinostat: possible involvement of reorientation of cortical microtubules.
abstract: Coleoptiles of rice (Oryza sativa L.) show a spontaneous (automorphic) curvature toward the caryopsis under microgravity conditions. The possible involvement of the reorientation of cortical microtubules in automorphic curvature was studied in rice coleoptiles grown on a three-dimensional clinostat. When rice seedlings that had been grown in the normal gravitational field were transferred to the clinostat in the dark, cortical microtubules of epidermal cells in the dorsal side of the coleoptiles oriented more transversely than the ventral side within 0.5 h. The rotation on the clinostat also increased the cell wall extensibility in the dorsal side and decreased the extensibility in the ventral side, and induced automorphic curvature. The reorientation of cortical microtubules preceded the changes in the cell wall extensibility and the curvature. The irradiation of rice seedlings with white light from above inhibited microtubule reorientation and changes in the cell wall extensibility, as well as curvature of coleoptiles. Also, colchicine, applied to the bending region of coleoptiles, partially inhibited the automorphic curvature. These results suggest that reorientation of cortical microtubules is involved in causing automorphic curvature in rice coleoptiles on the clinostat.
authors.affiliation: Department of Biology, Graduate School of Science, Osaka City University, Sugimoto, Sumiyoshi-ku, Japan.
authors.forename: Mizue
authors.initials: M
authors.lastname: Saiki
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Fujita
authors.forename: Kouichi
authors.initials: K
authors.lastname: Soga
authors.forename: Kazuyuki
authors.initials: K
authors.lastname: Wakabayashi
authors.forename: Seiichiro
authors.initials: S
authors.lastname: Kamisaka
authors.forename: Masamichi
authors.initials: M
authors.lastname: Yamashita
authors.forename: Takayuki
authors.initials: T
authors.lastname: Hoson
mesh_terms: D002473:Cell Wall / Q000648:ultrastructure; D003078:Colchicine / Q000494:pharmacology; D018548:Cotyledon / Q000166:cytology* / Q000187:drug effects / Q000528:radiation effects / Q000648:ultrastructure; D004305:Dose-Response Relationship, Drug; D008027:Light; D008870:Microtubules / Q000187:drug effects / Q000648:ultrastructure; D012275:Oryza / Q000166:cytology* / Q000187:drug effects / Q000528:radiation effects / Q000648:ultrastructure; D036226:Seedlings / Q000033:anatomy & histology* / Q000502:physiology; D013997:Time Factors
chemical_list: D003078:Colchicine