title: An oxidative and salinity stress induced peroxisomal ascorbate peroxidase from Avicennia marina: molecular and functional characterization.
abstract: APX (EC, 1.11.1.11) has a key role in scavenging ROS and in protecting cells against their toxic effects in algae and higher plants. A cDNA encoding a peroxisomal ascorbate peroxidase, Am-pAPX1, was isolated from salt stressed leaves of Avicennia marina (Forsk.) Vierh. by EST library screening and its expression in the context of various environmental stresses was investigated. Am-pAPX1 contains an ORF of 286 amino acids coding for a 31.4 kDa protein. The C-terminal region of the Am-pAPX1 ORF has a putative transmembrane domain and a peroxisomal targeting signal (RKKMK), suggesting peroxisomal localization. The peroxisomal localization of Am-pAPX1 was confirmed by stable transformation of the GFP-(Ala)(10)-Am-pAPX1 fusion in tobacco. RNA blot analysis revealed that Am-pAPX1 is expressed in response to salinity (NaCl) and oxidative stress (high intensity light, hydrogen peroxide application and excess iron). The isolated genomic clone of Am-pAPX1 was found to contain nine exons. A fragment of 1616bp corresponding to the 5' upstream region of Am-pAPX1 was isolated by TAIL-PCR. In silico analysis of this sequence reveals the presence of putative light and abiotic stress regulatory elements.
authors.affiliation: M.S. Swaminathan Research Foundation, Third Cross Street, Taramani Institutional Area, Chennai 600113, Tamilnadu, India.
authors.forename: Kumaresan
authors.initials: K
authors.lastname: Kavitha
authors.forename: Gayatri
authors.initials: G
authors.lastname: Venkataraman
authors.forename: Ajay
authors.initials: A
authors.lastname: Parida
mesh_terms: D000595:Amino Acid Sequence; D060387:Ascorbate Peroxidases; D032407:Avicennia / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics; D001483:Base Sequence; D018076:DNA, Complementary / Q000235:genetics; D020224:Expressed Sequence Tags; D006861:Hydrogen Peroxide / Q000494:pharmacology; D007501:Iron / Q000494:pharmacology; D008027:Light; D008969:Molecular Sequence Data; D018384:Oxidative Stress; D010544:Peroxidases / Q000235:genetics*; D020675:Peroxisomes / Q000201:enzymology / Q000235:genetics; D018515:Plant Leaves / Q000187:drug effects / Q000201:enzymology / Q000235:genetics; D010940:Plant Proteins / Q000235:genetics*; D030821:Plants, Genetically Modified / Q000187:drug effects / Q000201:enzymology / Q000235:genetics; D018749:RNA, Plant / Q000235:genetics; D054712:Salinity; D016415:Sequence Alignment; D014026:Nicotiana / Q000187:drug effects / Q000201:enzymology / Q000235:genetics
chemical_list: D018076:DNA, Complementary; D010940:Plant Proteins; D018749:RNA, Plant; D006861:Hydrogen Peroxide; D007501:Iron; D010544:Peroxidases; D060387:Ascorbate Peroxidases