title: Abscisic acid and blue light signaling pathways in chloroplast movements in Arabidopsis mesophyll.
abstract: Abscisic acid (ABA) and phototropins act antagonistically to control stomatal movements. Here, we investigated the role of ABA in phototropin-directed chloroplast movements in mesophyll cells of Arabidopsis thaliana. We analyzed the expression of phototropins at mRNA and protein level under the influence of ABA. PHOT1 mRNA level was decreased by ABA in the dark while it was insensitive to ABA in light. PHOT2 mRNA level was independent of the hormone treatment. The levels of phototropin proteins were down-regulated by ABA, both in darkness and light. No impact of exogenous ABA on amplitudes and kinetics of chloroplast movements was detected. Chloroplast responses in wild type Arabidopsis and three mutants, abi4, abi2 (abscisic acid insensitive4, 2) and aba1 (abscisic acid1), were measured to account for endogenous ABA signaling. The chloroplast responses were slightly reduced in abi2 and aba1 mutants in strong light. To further investigate the effect, abi2 and aba1 mutants were supplemented with exogenous ABA. In the aba1 mutant, the reaction was rescued but in abi2 it was unaffected. Our results show that ABA is not directly involved in phototropin-controlled chloroplast responses in mature leaves of Arabidopsis. However, the disturbance of ABA biosynthesis and signaling in mutants affects some elements of the chloroplast movement mechanism. In line with its role as a stress hormone, ABA appears to enhance plant sensitivity to light and promote the chloroplast avoidance response.
authors.affiliation: Jagiellonian University, Faculty of Biophysics, Biochemistry and Biotechnology, Department of Plant Biotechnology, Kraków, Poland.
authors.forename: Aleksandra
authors.initials: A
authors.lastname: Eckstein
authors.affiliation: Jagiellonian University, Faculty of Biophysics, Biochemistry and Biotechnology, Department of Plant Biotechnology, Kraków, Poland.
authors.forename: Weronika
authors.initials: W
authors.lastname: Krzeszowiec
authors.affiliation: Jagiellonian University, Faculty of Biophysics, Biochemistry and Biotechnology, Department of Plant Biotechnology, Kraków, Poland.
authors.forename: Agnieszka Katarzyna
authors.initials: AK
authors.lastname: Banaś
authors.affiliation: The Franciszek Górski Institute of Plant Physiology of Polish Academy of Sciences, Kraków, Poland.
authors.forename: Franciszek
authors.initials: F
authors.lastname: Janowiak
authors.affiliation: Jagiellonian University, Faculty of Biophysics, Biochemistry and Biotechnology, Department of Plant Biotechnology, Kraków, Poland.
authors.forename: Halina
authors.initials: H
authors.lastname: Gabryś
mesh_terms: D000040:Abscisic Acid / Q000494:pharmacology*; D017360:Arabidopsis / Q000166:cytology* / Q000235:genetics / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D001692:Biological Transport / Q000187:drug effects / Q000528:radiation effects; D002736:Chloroplasts / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D015870:Gene Expression; D018506:Gene Expression Regulation, Plant / Q000187:drug effects / Q000528:radiation effects; D008027:Light; D058503:Mesophyll Cells / Q000378:metabolism* / Q000648:ultrastructure; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism; D010937:Plant Growth Regulators / Q000494:pharmacology*; D018515:Plant Leaves / Q000166:cytology / Q000235:genetics / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases; D015398:Signal Transduction / Q000187:drug effects / Q000528:radiation effects
chemical_list: D029681:Arabidopsis Proteins; C423903:PHOT2 protein, Arabidopsis; D010750:Phosphoproteins; D010937:Plant Growth Regulators; D000040:Abscisic Acid; C103646:NPH1 protein, Arabidopsis; D017346:Protein Serine-Threonine Kinases