title: A cell-free system for light-dependent nuclear import of phytochrome.
abstract: Translocation from the cytosol to the nucleus is an essential step in phytochrome (phy) signal transduction. In the case of phytochrome A (phyA), this step occurs with the help of FHY1 (far-red-elongated hypocotyl 1), a specific transport protein. To investigate the components involved in phyA transport, we used a cell-free system that facilitates the controlled addition of transport factors. For this purpose, we isolated nuclei from the unicellular green algae Acetabularia acetabulum. These nuclei are up to 100 mum in diameter and allow easy detection of imported proteins. Experiments with isolated nuclei of Acetabularia showed that FHY1 is sufficient for phyA transport. The reconstituted system demonstrates all the characteristics of phytochrome transport in Arabidopsis thaliana. In addition, FHY1 was also actively exported from the nucleus, consistent with its role as a shuttle protein in plants. Therefore, we believe that isolated Acetabularia nuclei may be used as a general tool to study nuclear transport of plant proteins.
authors.affiliation: Plant Physiology, Faculty of Biology, University of Freiburg, Schaenzlestrasse 1, D-79104 Freiburg, Germany.
authors.forename: Anne
authors.initials: A
authors.lastname: Pfeiffer
authors.forename: Tim
authors.initials: T
authors.lastname: Kunkel
authors.forename: Andreas
authors.initials: A
authors.lastname: Hiltbrunner
authors.forename: Gunther
authors.initials: G
authors.lastname: Neuhaus
authors.forename: Iris
authors.initials: I
authors.lastname: Wolf
authors.forename: Volker
authors.initials: V
authors.lastname: Speth
authors.forename: Eva
authors.initials: E
authors.lastname: Adam
authors.forename: Ferenc
authors.initials: F
authors.lastname: Nagy
authors.forename: Eberhard
authors.initials: E
authors.lastname: Schäfer
mesh_terms: D000076:Acetabularia / Q000648:ultrastructure*; D021581:Active Transport, Cell Nucleus / Q000528:radiation effects; D029681:Arabidopsis Proteins / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism*; D002474:Cell-Free System; D008027:Light; D010834:Phytochrome / Q000378:metabolism; D051942:Phytochrome A / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; C441269:FHY1 protein, Arabidopsis; D051942:Phytochrome A; D010834:Phytochrome