title: Abscisic acid signalling determines susceptibility of bundle sheath cells to photoinhibition in high light-exposed Arabidopsis leaves.
abstract: The rapid induction of the bundle sheath cell (BSC)-specific expression of ASCORBATE PEROXIDASE2 (APX2) in high light (HL)-exposed leaves of Arabidopsis thaliana is, in part, regulated by the hormone abscisic acid (ABA) produced by vascular parenchyma cells. In this study, we provide more details of the ABA signalling that regulates APX2 expression and consider its importance in the photosynthetic responses of BSCs and whole leaves. This was done using a combination of analyses of gene expression and chlorophyll a fluorescence of both leaves and individual BSCs and mesophyll cells. The regulation of APX2 expression occurs by the combination of the protein kinase SnRK2.6 (OST1):protein phosphatase 2C ABI2 and a Gα (GPA1)-regulated signalling pathway. The use of an ost1-1/gpa1-4 mutant established that these signalling pathways are distinct but interact to regulate APX2. In HL-exposed leaves, BSC chloroplasts were more susceptible to photoinhibition than those of mesophyll cells. The activity of the ABA-signalling network determined the degree of susceptibility of BSCs to photoinhibition by influencing non-photochemical quenching. By contrast, in HL-exposed whole leaves, ABA signalling did not have any major influence on their transcriptomes nor on their susceptibility to photoinhibition, except where guard cell responses were observed.
authors.affiliation: Department of Genetics, Breeding and Plant Biotechnology, Warsaw University of Life Sciences, , Nowoursynowska Street 159, Warszawa 02-776, Poland.
authors.forename: Magdalena
authors.initials: M
authors.lastname: Gorecka
authors.forename: Ruben
authors.initials: R
authors.lastname: Alvarez-Fernandez
authors.forename: Katie
authors.initials: K
authors.lastname: Slattery
authors.forename: Lorna
authors.initials: L
authors.lastname: McAusland
authors.forename: Phillip A
authors.initials: PA
authors.lastname: Davey
authors.forename: Stanislaw
authors.initials: S
authors.lastname: Karpinski
authors.forename: Tracy
authors.initials: T
authors.lastname: Lawson
authors.forename: Philip M
authors.initials: PM
authors.lastname: Mullineaux
mesh_terms: D000040:Abscisic Acid / Q000378:metabolism*; D017360:Arabidopsis / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000378:metabolism; D060387:Ascorbate Peroxidases / Q000378:metabolism; D017931:DNA Primers / Q000235:genetics; D005453:Fluorescence; D044385:GTP-Binding Protein alpha Subunits / Q000378:metabolism; D018506:Gene Expression Regulation, Plant / Q000502:physiology*; D005838:Genotype; D008027:Light; D058503:Mesophyll Cells / Q000378:metabolism; D018515:Plant Leaves / Q000166:cytology / Q000502:physiology*; D011494:Protein Kinases / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*
chemical_list: D029681:Arabidopsis Proteins; D017931:DNA Primers; C429765:GPA1 protein, Arabidopsis; D044385:GTP-Binding Protein alpha Subunits; D017382:Reactive Oxygen Species; D000040:Abscisic Acid; C555293:APX2 protein, Arabidopsis; D060387:Ascorbate Peroxidases; D011494:Protein Kinases; C472139:OST1 protein, Arabidopsis
keywords: APX2; abscisic acid; bundle sheath cells; high light; photoinhibition; reactive oxygen species (ROS)