title: Light, genotype, and abscisic acid affect chloroplast positioning in guard cells of Arabidopsis thaliana leaves in distinct ways.
abstract: The goal of this study was to investigate the effects of light intensity, genotype, and various chemical treatments on chloroplast movement in guard cells of Arabidopsis thaliana leaves. After treatment at various light intensities (dark, low, and high light), leaf discs were fixed with glutaraldehyde, and imaged using confocal laser microscopy. Each chloroplast was assigned a horizontal (close to pore, center, or epidermal side) and vertical (outer, middle, inner) position. White light had a distinct effect on chloroplast positioning, most notably under high light (HL) when chloroplasts on the upper leaf surface of wild-type (WT) moved from epidermal and center positions toward the pore. This was not the case for phot1-5/phot2-1 or phot2-1 plants, thus phototropins are essential for chloroplast positioning in guard cells. In npq1-2 mutants, fewer chloroplasts moved to the pore position under HL than in WT plants, indicating that white light can affect chloroplast positioning also in a zeaxanthin-dependent way. Cytochalasin B inhibited the movement of chloroplasts to the pore under HL, while oryzalin did not, supporting the idea that actin plays a role in the movement. The movement along actin cables is dependent on CHUP1 since chloroplast positioning in chup1 was significantly altered. Abscisic acid (ABA) caused most chloroplasts in WT and phot1-5/phot2-1 to be localized in the center, middle part of the guard cells irrespective of light treatment. This indicates that not only light but also water stress influences chloroplast positioning.
authors.affiliation: Department of Biological Sciences, Wellesley College, Wellesley, MA 02481, USA. mkoniger@wellesley.edu
authors.forename: Martina
authors.initials: M
authors.lastname: Königer
authors.forename: Brita
authors.initials: B
authors.lastname: Jessen
authors.forename: Rui
authors.initials: R
authors.lastname: Yang
authors.forename: Dorothea
authors.initials: D
authors.lastname: Sittler
authors.forename: Gary C
authors.initials: GC
authors.lastname: Harris
mesh_terms: D000040:Abscisic Acid / Q000494:pharmacology*; D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics / Q000378:metabolism* / Q000528:radiation effects; D029681:Arabidopsis Proteins / Q000235:genetics; D060365:Chloroplast Proteins; D002736:Chloroplasts / Q000187:drug effects / Q000235:genetics / Q000378:metabolism* / Q000528:radiation effects; D003571:Cytochalasin B / Q000494:pharmacology; D004136:Dinitrobenzenes / Q000494:pharmacology; D005838:Genotype; D008027:Light; D008840:Microfilament Proteins / Q000235:genetics; D018613:Microscopy, Confocal; D010750:Phosphoproteins / Q000235:genetics; D010937:Plant Growth Regulators / Q000494:pharmacology; D018515:Plant Leaves / Q000187:drug effects / Q000235:genetics / Q000378:metabolism* / Q000528:radiation effects; D017346:Protein Serine-Threonine Kinases; D013424:Sulfanilamides / Q000494:pharmacology; D024341:Xanthophylls / Q000378:metabolism; D065146:Zeaxanthins
chemical_list: D029681:Arabidopsis Proteins; D060365:Chloroplast Proteins; D004136:Dinitrobenzenes; D008840:Microfilament Proteins; C423903:PHOT2 protein, Arabidopsis; D010750:Phosphoproteins; D010937:Plant Growth Regulators; D013424:Sulfanilamides; D024341:Xanthophylls; D065146:Zeaxanthins; C483724:chloroplast unusual positioning1 protein, Arabidopsis; D003571:Cytochalasin B; C012465:oryzalin; D000040:Abscisic Acid; C103646:NPH1 protein, Arabidopsis; D017346:Protein Serine-Threonine Kinases