title: Sulfite oxidase controls sulfur metabolism under SO2 exposure in Arabidopsis thaliana.
abstract: In the present study, the significance of sulfite oxidase (SO) for sulfite detoxification and sulfur assimilation was investigated. In response to sulfur dioxide (SO(2)) exposure, a remarkable expansion of sulfate and a significant increase of GSH pool were observed in wild-type and SO-overexpressing Arabidopsis. These metabolic changes were connected with a negative feedback inhibition of adenosine 5'-phosphosulfate reductase (APR), but no alterations in gas exchange parameters or visible symptoms of injury. However, Arabidopsis SO-KO mutants were consistently negatively affected upon 600 nL L(-1) SO(2) exposure for 60 h and showed phenotypical symptoms of injury with small necrotic spots on the leaves. The mean g(H2O) was reduced by about 60% over the fumigation period, accompanied by a reduction of net CO(2) assimilation and SO(2) uptake of about 50 and 35%. Moreover, sulfur metabolism was completely distorted. Whereas sulfate pool was kept constant, thiol-levels strongly increased. This demonstrates that SO should be the only protagonist for back-oxidizing and detoxification of sulfite. Based on these results, it is suggested that co-regulation of SO and APR controls sulfate assimilation pathway and stabilizes sulfite distribution into organic sulfur compounds. In conclusion, a sulfate-sulfite cycle driven by APR and SO can be postulated for fine-tuning of sulfur distribution that is additionally used for sulfite detoxification, when plants are exposed to atmospheric SO(2).
authors: Institut für Forstbotanik und Baumphysiologie, Albert-Ludwigs-Universität Freiburg, Georges-Köhler Allee 53/54, D-79085 Freiburg, Germany.
authors: Dörte
authors: D
authors: Randewig
authors: Domenica
authors: D
authors: Hamisch
authors: Cornelia
authors: C
authors: Herschbach
authors: Monika
authors: M
authors: Eiblmeier
authors: Christian
authors: C
authors: Gehl
authors: Jens
authors: J
authors: Jurgeleit
authors: Jessica
authors: J
authors: Skerra
authors: Ralf R
authors: RR
authors: Mendel
authors: Heinz
authors: H
authors: Rennenberg
authors: Robert
authors: R
authors: Hänsch
mesh_terms: D017360:Arabidopsis / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics; D001692:Biological Transport / Q000187:drug effects; D002245:Carbon Dioxide / Q000378:metabolism; D018506:Gene Expression Regulation, Plant / Q000187:drug effects*; D055786:Gene Knockout Techniques; D010641:Phenotype; D018515:Plant Leaves / Q000187:drug effects / Q000201:enzymology / Q000235:genetics / Q000254:growth & development; D030821:Plants, Genetically Modified; D013431:Sulfates / Q000032:analysis / Q000378:metabolism; D013438:Sulfhydryl Compounds / Q000032:analysis; D050876:Sulfite Oxidase / Q000235:genetics / Q000378:metabolism*; D013455:Sulfur / Q000378:metabolism*; D013458:Sulfur Dioxide / Q000494:pharmacology*
chemical_list: D013431:Sulfates; D013438:Sulfhydryl Compounds; D013458:Sulfur Dioxide; D002245:Carbon Dioxide; D013455:Sulfur; D050876:Sulfite Oxidase