title: Blue-light-activated phototropin2 trafficking from the cytoplasm to Golgi/post-Golgi vesicles.
abstract: Phototropins are plasma membrane-localized UVA/blue light photoreceptors which mediate phototropism, inhibition of primary hypocotyl elongation, leaf positioning, chloroplast movements, and stomatal opening. Blue light irradiation activates the C-terminal serine/threonine kinase domain of phototropin which autophosphorylates the receptor. Arabidopsis thaliana encodes two phototropins, phot1 and phot2. In response to blue light, phot1 moves from the plasma membrane into the cytosol and phot2 translocates to the Golgi complex. In this study the molecular mechanism and route of blue-light-induced phot2 trafficking are demonstrated. It is shown that Atphot2 behaves in a similar manner when expressed transiently under 35S or its native promoter. The phot2 kinase domain but not blue-light-mediated autophosphorylation is required for the receptor translocation. Using co-localization and western blotting, the receptor was shown to move from the cytoplasm to the Golgi complex, and then to the post-Golgi structures. The results were confirmed by brefeldin A (an inhibitor of the secretory pathway) which disrupted phot2 trafficking. An association was observed between phot2 and the light chain2 of clathrin via bimolecular fluorescence complementation. The fluorescence was observed at the plasma membrane. The results were confirmed using co-immunoprecipitation. However, tyrphostin23 (an inhibitor of clathrin-mediated endocytosis) and wortmannin (a suppressor of receptor endocytosis) were not able to block phot2 trafficking, indicating no involvement of receptor endocytosis in the formation of phot2 punctuate structures. Protein turnover studies indicated that the receptor was continuously degraded in both darkness and blue light. The degradation of phot2 proceeded via a transport route different from translocation to the Golgi complex.
authors.affiliation: Department of Plant Biotechnology, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, Gronostajowa 7, 30-387 Krakow, Poland.
authors.forename: Chhavi
authors.initials: C
authors.lastname: Aggarwal
authors.affiliation: Department of Plant Biotechnology, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, Gronostajowa 7, 30-387 Krakow, Poland.
authors.forename: Agnieszka Katarzyna
authors.initials: AK
authors.lastname: Banaś
authors.affiliation: Department of Molecular and Cellular Biology, Faculty of Biology, Adam Mickiewicz University, Umultowska 89, 61-614 Poznan, Poland.
authors.forename: Anna
authors.initials: A
authors.lastname: Kasprowicz-Maluśki
authors.affiliation: Department of Plant Biotechnology, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, Gronostajowa 7, 30-387 Krakow, Poland.
authors.forename: Carolina
authors.initials: C
authors.lastname: Borghetti
authors.affiliation: Department of Plant Biotechnology, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, Gronostajowa 7, 30-387 Krakow, Poland.
authors.forename: Justyna
authors.initials: J
authors.lastname: Labuz
authors.affiliation: Laboratory of Cell Biophysics, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, Gronostajowa 7, 30-387 Krakow, Poland.
authors.forename: Jerzy
authors.initials: J
authors.lastname: Dobrucki
authors.affiliation: Department of Plant Biotechnology, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, Gronostajowa 7, 30-387 Krakow, Poland halina.gabrys@uj.edu.pl.
authors.forename: Halina
authors.initials: H
authors.lastname: Gabryś
mesh_terms: D017360:Arabidopsis / Q000166:cytology / Q000235:genetics* / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism*; D006056:Golgi Apparatus / Q000378:metabolism*; D047468:Immunoprecipitation; D008027:Light; D010766:Phosphorylation; D010770:Phosphotransferases / Q000378:metabolism; D021381:Protein Transport / Q000528:radiation effects
chemical_list: D029681:Arabidopsis Proteins; C423903:PHOT2 protein, Arabidopsis; D010770:Phosphotransferases
keywords: Arabidopsis thaliana; Golgi complex; blue light; degradation; phototropin; trafficking.