title: Gravitaxis in Chlamydomonas reinhardtii: characterization using video microscopy and computer analysis.
abstract: We characterized the gravitactic behavior of Chlamydomonas reinhardtii, a unicellular green alga, using a computer-analysis system in order to study directional swimming. The effects of the calcium-channel inhibitors gadolinium and diltiazem on graviorientation and swimming speed were examined. In addition, we studied directional swimming in the ptx1 strain of C. reinhardtii, a flagellar dominance mutant. Results indicate that Chlamydomonas reorients for gravitactic swimming through a mechanism different from the calcium-mediated pathway believed to be involved in gravity transduction in higher plants. We suggest that calcium-mediated gravitaxis originated in an organism that was more evolutionarily advanced than Chlamydomonas.
authors.affiliation: Department of Plant and Microbial Biology, University of California, Berkeley 94720, USA.
authors.forename: V
authors.initials: V
authors.lastname: Kam
authors.forename: N
authors.initials: N
authors.lastname: Moseyko
authors.forename: J
authors.initials: J
authors.lastname: Nemson
authors.forename: L J
authors.initials: LJ
authors.lastname: Feldman
mesh_terms: D000818:Animals; D002121:Calcium Channel Blockers / Q000494:pharmacology; D016825:Chlamydomonas reinhardtii / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D004110:Diltiazem / Q000494:pharmacology; D004121:Dimethyl Sulfoxide / Q000494:pharmacology; D005682:Gadolinium / Q000494:pharmacology; D006112:Gravitation; D018466:Gravity Sensing / Q000187:drug effects / Q000502:physiology*; D007091:Image Processing, Computer-Assisted; D018715:Microscopy, Video; D009043:Motor Activity / Q000187:drug effects / Q000502:physiology; D009154:Mutation; D009949:Orientation / Q000187:drug effects / Q000502:physiology*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D012997:Solvents / Q000494:pharmacology; D013550:Swimming
chemical_list: D002121:Calcium Channel Blockers; D012997:Solvents; D005682:Gadolinium; D004110:Diltiazem; D004121:Dimethyl Sulfoxide