Circadian Rhythms of Isoprene Biosynthesis in Grey Poplar Leaves

• Published in: Plant physiology (Bethesda) Vol. 143; no. 1; pp. 540 - 551
• Main Authors: Loivamäki, Maaria, Louis, Sandrine, Cinege, Gyöngyi, Zimmer, Ina, Fischbach, Robert J, Schnitzler, Jörg-Peter
• Format: Journal Article
• Language: English
• Published: Rockville, MD American Society of Plant Biologists 2007; American Society of Plant Physiologists
• Subjects: Alkyl and Aryl Transferases - genetics; Alkyl and Aryl Transferases - metabolism; Base Sequence; Biological and medical sciences; Biosynthesis; Butadienes; Circadian Rhythm; DNA-Binding Proteins - metabolism; Enzymes; Fundamental and applied biological sciences. Psychology; Gene expression; Gene expression regulation; Gene Expression Regulation, Plant; Genes; Hemiterpenes - biosynthesis; Leaves; Metabolism; Metabolism. Physicochemical requirements; Molecular Sequence Data; Pentanes; Photoperiod; Plant Leaves - genetics; Plant Leaves - metabolism; Plant Leaves - radiation effects; Plant physiology and development; Plant Proteins - metabolism; Plant Shoots - genetics; Plant Shoots - metabolism; Plant Shoots - radiation effects; Plants; Pollutant emissions; Populus - genetics; Populus - metabolism; Populus - radiation effects; Promoter regions; Promoter Regions, Genetic; Systems Biology, Molecular Biology, and Gene Regulation; Terpenoids; Transcription Factors - metabolism; Biosynthesis; Plant leaf; Circadian rhythm
• ISSN: 0032-0889; 1532-2548
• DOI: 10.1104/pp.106.092759

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.