title: Calcium mobilizations in response to changes in the gravity vector in Arabidopsis seedlings: possible cellular mechanisms.
abstract: Gravity influences the growth direction of higher plants. Changes in the gravity vector (gravistimulation) immediately promote the increase in the cytoplasmic free calcium ion concentration ([Ca(2+)]c) in Arabidopsis (Arabidopsis thaliana) seedlings. When the seedlings are gravistimulated by reorientation at 180°, a transient two peaked (biphasic) [Ca(2+)]c-increase arises in their hypocotyl and petioles. Parabolic flights (PFs) can generate a variety of gravity-stimuli, and enables us to measure gravity-induced [Ca(2+)]c-increases without specimen rotation, which demonstrate that Arabidopsis seedlings possess a rapid gravity-sensing mechanism linearly transducing a wide range of gravitational changes into Ca(2+) signals on a sub-second timescale. Hypergravity by centrifugation (20 g or 300 g) also induces similar transient [Ca(2+)]c-increases. In this review, we propose models for possible cellular processes of the garavi-stimulus-induced [Ca(2+)]c-increase, and evaluate those by examining whether the model fits well with the kinetic parameters derived from the [Ca(2+)]c-increases obtained by applying gravistimulus with different amplitudes and time sequences.
authors.affiliation: a Nagoya University Graduate School of Medicine; Nagoya, Japan.
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Tatsumi
authors.forename: Masatsugu
authors.initials: M
authors.lastname: Toyota
authors.forename: Takuya
authors.initials: T
authors.lastname: Furuichi
authors.forename: Masahiro
authors.initials: M
authors.lastname: Sokabe
mesh_terms: D017360:Arabidopsis / Q000254:growth & development / Q000378:metabolism / Q000502:physiology*; D002118:Calcium / Q000378:metabolism*; D006112:Gravitation; D018522:Gravitropism; D018466:Gravity Sensing; D036226:Seedlings / Q000378:metabolism / Q000502:physiology*; D015398:Signal Transduction
chemical_list: D002118:Calcium
keywords: actin filament; calcium; gravistimulation; kinetics; mechanosensitive channel; parabolic flight; starch-statolish hypothesis