title: cDNA cloning and differential expression patterns of ascorbate peroxidase during post-harvest in Brassica rapa L.
abstract: Ascorbate is an antioxidant and a cofactor of many dioxygenases in plant and animal cell metabolism. A well-recognized enzyme consuming ascorbate is ascorbate peroxidase (APX), which catalyses the reduction of hydrogen peroxide to water with the simultaneous oxidation of ascorbate with a high specificity. The isolation and characterisation of new Apx cDNAs, could provide new insights about the physiological roles and regulation of these enzymes. In this work chloroplastic (Br-chlApx) and cytosolic (Br-cApx) isoform transcripts were isolated by RT-PCR in Brassica rapa and expression changes were analysed by semi-quantitative RT-PCR performed in different tissues (layer, stalk and florets) at different days (0, 4 and 14 day). The result showed that BrApx isoforms were differentially expressed and the Br-chlApx, in particular in the layer, had the highest expression level and remained unchanged also after 14 day after harvest. In addition, expression changes were compared with total BrAPX activity and the results showed that the activity decreased in all tissues at 14 day after harvest, independently of transcripts. Finally, additional solutes as the substrate of APX ascorbate and its oxidized form, dehydroascorbate, as well as α-tocopherol, the major vitamin E compound that prevents the propagation of lipid peroxidation in thylakoid membranes, were followed. The changes in the BrApx expression, BrAPX activity and metabolites can provide further evidence of the close relationships that exist between antioxidants which compensate for each other and suggest that there are multiple sites of reciprocal control.
authors.affiliation: Department of Life Science, II University of Naples, via Vivaldi 43, 81100 Caserta, Italy. linawoodrow@libero.it
authors.forename: Pasqualina
authors.initials: P
authors.lastname: Woodrow
authors.forename: Amodio
authors.initials: A
authors.lastname: Fuggi
authors.forename: Giovanni
authors.initials: G
authors.lastname: Pontecorvo
authors.forename: Ioannis
authors.initials: I
authors.lastname: Kafantaris
authors.forename: Maria Grazia
authors.initials: MG
authors.lastname: Annunziata
authors.forename: Giuseppina
authors.initials: G
authors.lastname: Massaro
authors.forename: Petronia
authors.initials: P
authors.lastname: Carillo
mesh_terms: D060387:Ascorbate Peroxidases / Q000235:genetics* / Q000378:metabolism; D029741:Brassica rapa / Q000201:enzymology* / Q000235:genetics; D003001:Cloning, Molecular; D018076:DNA, Complementary; D004789:Enzyme Activation; D015870:Gene Expression; D018506:Gene Expression Regulation, Plant; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D055442:Metabolome; D008969:Molecular Sequence Data; D014158:Transcription, Genetic
chemical_list: D018076:DNA, Complementary; D007527:Isoenzymes; D060387:Ascorbate Peroxidases