title: Tissue-specific accumulation and regulation of zeaxanthin epoxidase in Arabidopsis reflect the multiple functions of the enzyme in plastids.
abstract: The enzyme zeaxanthin epoxidase (ZEP) catalyzes the conversion of zeaxanthin to violaxanthin, a key reaction for ABA biosynthesis and the xanthophyll cycle. Both processes are important for acclimation to environmental stress conditions, in particular drought (ABA biosynthesis) and light (xanthophyll cycle) stress. Hence, both ZEP functions may require differential regulation to optimize plant fitness. The key to understanding the function of ZEP in both stress responses might lie in its spatial and temporal distribution in plant tissues. Therefore, we analyzed the distribution of ZEP in plant tissues and plastids under drought and light stress by use of a ZEP-specific antibody. In addition, we determined the pigment composition of the plant tissues and chloroplast membrane subcompartments in response to these stresses. The ZEP protein was detected in all plant tissues (except flowers) concomitant with xanthophylls. The highest levels of ZEP were present in leaf chloroplasts and root plastids. Within chloroplasts, ZEP was localized predominantly in the thylakoid membrane and stroma, while only a small fraction was bound by the envelope membrane. Light stress affected neither the accumulation nor the relative distribution of ZEP in chloroplasts, while drought stress led to an increase of ZEP in roots and to a degradation of ZEP in leaves. However, drought stress-induced increases in ABA were similar in both tissues. These data support a tissue- and stress-specific accumulation of the ZEP protein in accordance with its different functions in ABA biosynthesis and the xanthophyll cycle.
authors.affiliation: Plant Biochemistry, Heinrich-Heine-University Düsseldorf, D-40225 Düsseldorf, Germany.
authors.forename: Nadine
authors.initials: N
authors.lastname: Schwarz
authors.affiliation: Carnegie Institution for Science, Department of Plant Biology, Stanford, CA 94305, USA Department of Plant and Microbial Biology, University of California, Berkeley, CA, USA.
authors.forename: Ute
authors.initials: U
authors.lastname: Armbruster
authors.affiliation: Plant Biochemistry, Albrecht-von-Haller-Institute for Plant Sciences, Georg-August-University Göttingen, D-37077 Göttingen, Germany.
authors.forename: Tim
authors.initials: T
authors.lastname: Iven
authors.affiliation: Plant Biochemistry, Heinrich-Heine-University Düsseldorf, D-40225 Düsseldorf, Germany.
authors.forename: Lena
authors.initials: L
authors.lastname: Brückle
authors.affiliation: Physiology and Cell Biology, Leibniz Institute of Plant Genetics and Crop Plant Research (IPK), D-06466 Gatersleben, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Melzer
authors.affiliation: Plant Biochemistry, Albrecht-von-Haller-Institute for Plant Sciences, Georg-August-University Göttingen, D-37077 Göttingen, Germany.
authors.forename: Ivo
authors.initials: I
authors.lastname: Feussner
authors.affiliation: Plant Biochemistry, Heinrich-Heine-University Düsseldorf, D-40225 Düsseldorf, Germany pjahns@hhu.de.
authors.forename: Peter
authors.initials: P
authors.lastname: Jahns
mesh_terms: D000040:Abscisic Acid / Q000378:metabolism; D017360:Arabidopsis / Q000201:enzymology*; D029681:Arabidopsis Proteins / Q000378:metabolism*; D055864:Droughts; D007425:Intracellular Membranes / Q000201:enzymology; D009928:Organ Specificity; D010088:Oxidoreductases / Q000378:metabolism*; D010860:Pigments, Biological / Q000378:metabolism; D018515:Plant Leaves / Q000201:enzymology; D018517:Plant Roots / Q000201:enzymology; D018087:Plastids / Q000201:enzymology*; D021381:Protein Transport; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013312:Stress, Physiological; D020524:Thylakoids
chemical_list: D029681:Arabidopsis Proteins; D010860:Pigments, Biological; D011993:Recombinant Fusion Proteins; D000040:Abscisic Acid; D010088:Oxidoreductases; C097153:zeaxanthin epoxidase
keywords: Abscisic acid biosynthesis; Arabidopsis thaliana; Drought stress; Photo-oxidative stress; Xanthophyll cycle; Zeaxanthin epoxidase