title: Changes in phosphorylation of 50 and 53 kDa soluble proteins in graviresponding oat (Avena sativa) shoots.
abstract: The present work indicates that phosphorylation of a 50 kDa soluble protein is involved in the gravitropic response in graviresponsive pulvini of oat (Avena sativa) stems. This 50 kDa protein shows a differential pattern of phosphorylation between lower and upper halves of pulvini both in vivo and in vitro. The differential phosphorylation of this protein is detected only when stem segments are gravistimulated for short and long time periods. The differential phosphorylation of the 50 kDa protein occurs as early as 5 min after the initiation of gravistimulation. This corresponds closely to the presentation time of 5.2 min. This differential phosphorylation pattern was changed by treatments with cycloheximide, implying that a newly-synthesized protein is involved in the differential phosphorylation during the gravitropic response. An autophosphorylation experiment shows that the 50 kDa protein has kinase activity. The phosphorylation patterns of a 53 kDa protein were similar to those of the 50 kDa protein, but were only expressed in vitro. These findings indicate that the differential phosphorylation of the 50 (and 53 kDa) soluble proteins in graviresponding oat shoots may be an important component of the gravity signal transduction pathway.
authors.affiliation: Center for Cell Signaling Research, Ewha Woman's University, Seoul 120-750, Korea.
authors.forename: Soo Chul
authors.initials: SC
authors.lastname: Chang
authors.forename: Myeon Haeng
authors.initials: MH
authors.lastname: Cho
authors.forename: Seong-Ki
authors.initials: SK
authors.lastname: Kim
authors.forename: June Seung
authors.initials: JS
authors.lastname: Lee
authors.forename: Ara
authors.initials: A
authors.lastname: Kirakosyan
authors.forename: Peter B
authors.initials: PB
authors.lastname: Kaufman
mesh_terms: D018554:Avena / Q000502:physiology*; D046508:Culture Techniques; D003513:Cycloheximide / Q000494:pharmacology; D018522:Gravitropism / Q000187:drug effects / Q000502:physiology*; D018466:Gravity Sensing / Q000502:physiology*; D007811:Lanthanum / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects; D010940:Plant Proteins / Q000378:metabolism*; D018520:Plant Shoots / Q000502:physiology*; D015398:Signal Transduction / Q000187:drug effects
chemical_list: D010940:Plant Proteins; C028521:lanthanum chloride; D007811:Lanthanum; D003513:Cycloheximide