title: Molecular cloning of two novel peroxidases and their response to salt stress and salicylic acid in the living fossil Ginkgo biloba.
abstract: OBJECTIVE
  Peroxidase isoenzymes play diverse roles in plant physiology, such as lignification and defence against pathogens. The actions and regulation of many peroxidases are not known with much accuracy. A number of studies have reported direct involvement of peroxidase isoenzymes in the oxidation of monolignols, which constitutes the last step in the lignin biosynthesis pathway. However, most of the available data concern only peroxidases and lignins from angiosperms. This study describes the molecular cloning of two novel peroxidases from the 'living fossil' Ginkgo biloba and their regulation by salt stress and salicylic acid.
  
  
  METHODS
  Suspension cell cultures were used to purify peroxidases and to obtain the cDNAs. Treatments with salicylic acid and sodium chloride were performed and peroxidase activity and gene expression were monitored.
  
  
  RESULTS
  A novel peroxidase was purified, which preferentially used p-hydroxycinnamyl alcohols as substrates and was able to form dehydrogenation polymers in vitro from coniferyl and sinapyl alcohols. Two peroxidase full-length cDNAs, GbPrx09 and GbPrx10, were cloned. Both peroxidases showed high similarity to other basic peroxidases with a putative role in cell wall lignification. Both GbPrx09 and GbPrx10 were expressed in leaves and stems of the plant. Sodium chloride enhanced the gene expression of GbPrx09 but repressed GbPrx10, whereas salicylic acid strongly repressed both GbPrx09 and GbPrx10.
  
  
  CONCLUSIONS
  Taken together, the data suggest the participation of GbPrx09 and GbPrx10 in the developmental lignification programme of the cell wall. Both peroxidases possess the structural characteristics necessary for sinapyl alcohol oxidation. Moreover, GbPrx09 is also involved in lignification induced by salt stress, while salicylic acid-mediated lignification is not a result of GbPrx09 and GbPrx10 enzymatic activity.
authors.affiliation: Department of Plant Biology, University of Murcia, E-30100 Murcia, Spain Department of Animal Biology, Plant Biology and Ecology, University of A Coruña, E-15071 A Coruña, Spain enovo@um.es.
authors.forename: Esther
authors.initials: E
authors.lastname: Novo-Uzal
authors.affiliation: Department of Animal Biology, Plant Biology and Ecology, University of A Coruña, E-15071 A Coruña, Spain.
authors.forename: Jorge
authors.initials: J
authors.lastname: Gutiérrez
authors.affiliation: Department of Animal Biology, Plant Biology and Ecology, University of A Coruña, E-15071 A Coruña, Spain.
authors.forename: Teresa
authors.initials: T
authors.lastname: Martínez-Cortés
authors.affiliation: Department of Animal Biology, Plant Biology and Ecology, University of A Coruña, E-15071 A Coruña, Spain.
authors.forename: Federico
authors.initials: F
authors.lastname: Pomar
mesh_terms: D000595:Amino Acid Sequence; D002473:Cell Wall / Q000378:metabolism; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics; D005580:Fossils; D020441:Ginkgo biloba / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D008031:Lignin / Q000378:metabolism; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D009195:Peroxidase / Q000235:genetics* / Q000378:metabolism; D010802:Phylogeny; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D020005:Propanols / Q000032:analysis / Q000378:metabolism; D018749:RNA, Plant / Q000235:genetics; D020156:Salicylic Acid / Q000494:pharmacology; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D012965:Sodium Chloride / Q000494:pharmacology; D013312:Stress, Physiological
chemical_list: D018076:DNA, Complementary; D010940:Plant Proteins; D020005:Propanols; D018749:RNA, Plant; C439395:1-phenylpropanol; D012965:Sodium Chloride; D008031:Lignin; D009195:Peroxidase; D020156:Salicylic Acid
keywords: Ginkgo biloba; lignin; peroxidase; phenylpropanoid metabolism; plant cell wall; salicylic acid; salt stress; syringyl lignin