title: Circadian rhythms of isoprene biosynthesis in grey poplar leaves.
abstract: Isoprene (2-methyl-1,3-butadiene) emission varies diurnally in different species. In poplar (Populus spp.), it has recently been shown that the gene encoding the synthesizing enzyme for isoprene, isoprene synthase (ISPS), displays diurnal variation in expression. Working on shoot cultures of Grey poplar (Populus x canescens) placed under a different light regime in phytochambers, we showed that these variations in PcISPS gene expression, measured by quantitative real-time polymerase chain reaction, are not only due to day-night changes, but also are linked to an internal circadian clock. Measurement of additional selected isoprenoid genes revealed that phytoene synthase (carotenoid pathway) displays similar fluctuations, whereas 1-deoxy-d-xylulose 5-phosphate reductoisomerase, possibly the first committed enzyme of the 1-deoxy-d-xylulose 5-phosphate pathway, only shows light regulation. On the protein level, it appeared that PcISPS activity and protein content became reduced under constant darkness, whereas under constant light, activity and protein content of this enzyme were kept high. In contrast, isoprene emission rates under continuous irradiation displayed circadian changes as is the case for gene expression of PcISPS. Furthermore, binding assays with Arabidopsis (Arabidopsis thaliana) late elongated hypocotyl, a transcription factor of Arabidopsis involved in circadian regulation, clearly revealed the presence of circadian-determining regulatory elements in the promoter region of PcISPS.
authors.affiliation: Forschungszentrum Karlsruhe GmbH, Institut für Meteorologie und Klimaforschung, Atmosphärische Umweltforschung, 82467 Garmisch-Partenkirchen, Germany.
authors.forename: Maaria
authors.initials: M
authors.lastname: Loivamäki
authors.forename: Sandrine
authors.initials: S
authors.lastname: Louis
authors.forename: Gyöngyi
authors.initials: G
authors.lastname: Cinege
authors.forename: Ina
authors.initials: I
authors.lastname: Zimmer
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Fischbach
authors.forename: Jörg-Peter
authors.initials: JP
authors.lastname: Schnitzler
mesh_terms: D019883:Alkyl and Aryl Transferases / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D002070:Butadienes; D002940:Circadian Rhythm; D004268:DNA-Binding Proteins / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D045782:Hemiterpenes / Q000096:biosynthesis*; D008969:Molecular Sequence Data; D010420:Pentanes; D017440:Photoperiod; D018515:Plant Leaves / Q000235:genetics / Q000378:metabolism / Q000528:radiation effects; D010940:Plant Proteins / Q000378:metabolism; D018520:Plant Shoots / Q000235:genetics / Q000378:metabolism / Q000528:radiation effects; D032107:Populus / Q000235:genetics / Q000378:metabolism* / Q000528:radiation effects; D011401:Promoter Regions, Genetic; D014157:Transcription Factors / Q000378:metabolism
chemical_list: D002070:Butadienes; D004268:DNA-Binding Proteins; D045782:Hemiterpenes; C113192:LHY protein, Arabidopsis; D010420:Pentanes; D010940:Plant Proteins; D014157:Transcription Factors; C005059:isoprene; D019883:Alkyl and Aryl Transferases; C093854:isoprene synthase