title: Hydrotropic response and expression pattern of auxin-inducible gene, CS-IAA1, in the primary roots of clinorotated cucumber seedlings.
abstract: Primary roots of cucumber seedlings showed positive hydrotropism when exposed to a moisture gradient and rotated on a two-axis clinostat. To examine the role of auxin in the differential growth of the hydrotropically responding roots, we first examined the expression of auxin-inducible genes, CS-AUX/IAAs, in cucumber roots. After auxin starvation, mRNA levels of CS-IAA1 and CS-IAA3 decreased in the roots. Applying auxin to the auxin-starved roots resulted in accumulation of CS-IAA1 and CS-IAA3 mRNA. The level of expression of these genes increased when the auxin concentration was increased. CS-IAA1 mRNA accumulated in response to 10(-8) M auxin, and the level increased further, depending on the dose. Auxin starvation did not result in a decrease in the level of CS-IAA2 mRNA; however, adding exogenous auxin at concentrations higher than 10(-7) M increased its accumulation. In the primary roots responding hydrotropically or gravitropically, CS-IAA1 expression was greater on the concave side of the curving roots than on the convex side. The difference could be detected 30 min following stimulation by gravity or a moisture gradient, and that difference increased with time. These results support the idea that asymmetry of localization of auxin is associated with differential growth in hydrotropically responding roots.
authors.affiliation: Graduate School of Life Sciences, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, 980-8577 Japan.
authors.forename: Hidetoshi
authors.initials: H
authors.lastname: Mizuno
authors.forename: Akie
authors.initials: A
authors.lastname: Kobayashi
authors.forename: Nobuharu
authors.initials: N
authors.lastname: Fujii
authors.forename: Masamichi
authors.initials: M
authors.lastname: Yamashita
authors.forename: Hideyuki
authors.initials: H
authors.lastname: Takahashi
mesh_terms: D018553:Cucumis sativus / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D018522:Gravitropism / Q000187:drug effects / Q000502:physiology; D017403:In Situ Hybridization; D007210:Indoleacetic Acids / Q000494:pharmacology*; D010940:Plant Proteins / Q000378:metabolism; D018517:Plant Roots / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D018523:Tropism / Q000187:drug effects / Q000502:physiology*; D014867:Water / Q000494:pharmacology / Q000502:physiology*
chemical_list: D007210:Indoleacetic Acids; D010940:Plant Proteins; D012333:RNA, Messenger; D014867:Water