title: Fine tuning chloroplast movements through physical interactions between phototropins.
abstract: Phototropins are plant photoreceptors which regulate numerous responses to blue light, including chloroplast relocation. Weak blue light induces chloroplast accumulation, whereas strong light leads to an avoidance response. Two Arabidopsis phototropins are characterized by different light sensitivities. Under continuous light, both can elicit chloroplast accumulation, but the avoidance response is controlled solely by phot2. As well as continuous light, brief light pulses also induce chloroplast displacements. Pulses of 0.1s and 0.2s of fluence rate saturating the avoidance response lead to transient chloroplast accumulation. Longer pulses (up to 20s) trigger a biphasic response, namely transient avoidance followed by transient accumulation. This work presents a detailed study of transient chloroplast responses in Arabidopsis. Phototropin mutants display altered chloroplast movements as compared with the wild type: phot1 is characterized by weaker responses, while phot2 exhibits enhanced chloroplast accumulation, especially after 0.1s and 0.2s pulses. To determine the cause of these differences, the abundance and phosphorylation levels of both phototropins, as well as the interactions between phototropin molecules are examined. The formation of phototropin homo- and heterocomplexes is the most plausible explanation of the observed phenomena. The physiological consequences of this interplay are discussed, suggesting the universal character of this mechanism that fine-tunes plant reactions to blue light. Additionally, responses in mutants of different protein phosphatase 2A subunits are examined to assess the role of protein phosphorylation in signaling of chloroplast movements.
authors.affiliation: Department of Plant Biotechnology, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, Gronostajowa 7, 30-387 Krakow, Poland Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawińskiego 5a, 02-106 Warsaw, Poland olga.sztatelman@ibb.waw.pl.
authors.forename: Olga
authors.initials: O
authors.lastname: Sztatelman
authors.affiliation: Department of Plant Biotechnology, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, Gronostajowa 7, 30-387 Krakow, Poland Malopolska Centre of Biotechnology, Jagiellonian University, Gronostajowa 7A, 30-387 Krakow, Poland.
authors.forename: Justyna
authors.initials: J
authors.lastname: Łabuz
authors.affiliation: Department of Plant Biotechnology, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, Gronostajowa 7, 30-387 Krakow, Poland.
authors.forename: Paweł
authors.initials: P
authors.lastname: Hermanowicz
authors.affiliation: Department of Plant Biotechnology, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, Gronostajowa 7, 30-387 Krakow, Poland Malopolska Centre of Biotechnology, Jagiellonian University, Gronostajowa 7A, 30-387 Krakow, Poland.
authors.forename: Agnieszka Katarzyna
authors.initials: AK
authors.lastname: Banaś
authors.affiliation: Department of Plant Biotechnology, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, Gronostajowa 7, 30-387 Krakow, Poland Malopolska Centre of Biotechnology, Jagiellonian University, Gronostajowa 7A, 30-387 Krakow, Poland.
authors.forename: Aneta
authors.initials: A
authors.lastname: Bażant
authors.affiliation: Department of Plant Biotechnology, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, Gronostajowa 7, 30-387 Krakow, Poland.
authors.forename: Piotr
authors.initials: P
authors.lastname: Zgłobicki
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: Marcin
authors.initials: M
authors.lastname: Nadzieja
authors.affiliation: Department of Plant Biotechnology, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, Gronostajowa 7, 30-387 Krakow, Poland.
authors.forename: Weronika
authors.initials: W
authors.lastname: Krzeszowiec
authors.affiliation: Department of Plant Biotechnology, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, Gronostajowa 7, 30-387 Krakow, Poland.
authors.forename: Wojciech
authors.initials: W
authors.lastname: Strzałka
authors.affiliation: Department of Plant Biotechnology, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, Gronostajowa 7, 30-387 Krakow, Poland Malopolska Centre of Biotechnology, Jagiellonian University, Gronostajowa 7A, 30-387 Krakow, Poland.
authors.forename: Halina
authors.initials: H
authors.lastname: Gabryś
mesh_terms: D017360:Arabidopsis / Q000378:metabolism / Q000502:physiology / Q000528:radiation effects; D029681:Arabidopsis Proteins / Q000378:metabolism / Q000502:physiology; D002736:Chloroplasts / Q000378:metabolism / Q000502:physiology* / Q000528:radiation effects; D008027:Light; D056949:Phototropins / Q000378:metabolism / Q000502:physiology*; D020798:Two-Hybrid System Techniques
chemical_list: D029681:Arabidopsis Proteins; D056949:Phototropins
keywords: Arabidopsis thaliana; blue light; chloroplast movements; light pulses; phototropin1; phototropin2; protein phosphatase 2A.