title: Molecular cloning and characterization of violaxanthin de-epoxidase (CsVDE) in cucumber.
abstract: Violaxanthin de-epoxidase (VDE) plays an important role in protecting the photosynthetic apparatus from photo-damage by dissipating excessively absorbed light energy as heat, via the conversion of violaxanthin (V) to intermediate product antheraxanthin (A) and final product zeaxanthin (Z) under high light stress. We have cloned a violaxanthin de-epoxidase gene (CsVDE) from cucumber. The amino acid sequence of CsVDE has high homology with VDEs in other plants. RT-PCR analysis and histochemical staining show that CsVDE is expressed in all green tissues in cucumber and Arabidopsis. Using GFP fusion protein and immunogold labeling methods, we show that CsVDE is mainly localized in chloroplasts in cucumber. Under high light stress, relative expression of CsVDE and the de-epoxidation ratio (A+Z)/(V+A+Z) is increased rapidly, and abundance of the gold particles was also increased. Furthermore, CsVDE is quickly induced by cold and drought stress, reaching maximum levels at the 2(nd) hour and the 9(th) day, respectively. The ratio of (A+Z)/(V+A+Z) and non-photochemical quenching (NPQ) is reduced in transgenic Arabidopsis down-regulated by the antisense fragment of CsVDE, compared to wild type (WT) Arabidopsis under high light stress. This indicates decreased functionality of the xanthophyll cycle and increased sensitivity to photoinhibition of photosystem II (PSII) in transgenic Arabidopsis under high light stress.
authors.affiliation: Beijing Key Laboratory of Growth and Developmental Regulation for Protected Vegetable Crops, China Agricultural University, Beijing, China.
authors.forename: Xin
authors.initials: X
authors.lastname: Li
authors.forename: Wenchao
authors.initials: W
authors.lastname: Zhao
authors.forename: Xiyan
authors.initials: X
authors.lastname: Sun
authors.forename: Hongyu
authors.initials: H
authors.lastname: Huang
authors.forename: Lingcui
authors.initials: L
authors.lastname: Kong
authors.forename: Dandan
authors.initials: D
authors.lastname: Niu
authors.forename: Xiaolei
authors.initials: X
authors.lastname: Sui
authors.forename: Zhenxian
authors.initials: Z
authors.lastname: Zhang
mesh_terms: D000595:Amino Acid Sequence; D003001:Cloning, Molecular; D003080:Cold Temperature; D018553:Cucumis sativus / Q000201:enzymology* / Q000235:genetics; D055864:Droughts; D049452:Green Fluorescent Proteins / Q000235:genetics; D008969:Molecular Sequence Data; D010088:Oxidoreductases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D010802:Phylogeny; D030821:Plants, Genetically Modified; D017386:Sequence Homology, Amino Acid; D013347:Subcellular Fractions / Q000201:enzymology
chemical_list: D049452:Green Fluorescent Proteins; D010088:Oxidoreductases; C023290:violaxanthin de-epoxidase