title: Temperature controls on the basal emission rate of isoprene in a tropical tree Ficus septica: exploring molecular regulatory mechanisms.
abstract: Isoprene emission from plants is very sensitive to environmental temperature both at short-term and long-term scales. Our previous study demonstrated suppression of isoprene emission by cold temperatures in a high emitting tropical tree Ficus septica and revealed a strong correlation of emission to isoprene synthase (IspS) protein levels. When challenged with decreasing daily temperatures from 30 to 12 °C, F. septica completely stopped isoprene emission at 12 °C, only to recover on the second day after re-exposure to 30 °C. Here, we explored this regulation of isoprene emission in response to environmental temperature by a comprehensive analysis of transcriptome data, gene expressions and metabolite pools of the 2-C-methyl-D-erythritol 4-phosphate (MEP) pathway. MEP pathway genes and metabolites dynamics did not support substrate-level limitations as major control over observed basal emission, but transcriptome data, network inferences and putative regulatory elements on IspS promoter suggested transcriptional regulation of IspS gene through circadian rhythm and phytohormone signalling processes. Expression levels of 29 genes involved in these pathways were examined by quantitative real-time PCR. We propose that temperature controls over basal isoprene emission at a time-scale of hours to few days are regulated by phytohormone-mediated transcriptional modulation of IspS gene under synchronization by the circadian clock.
authors.affiliation: United Graduate School of Agricultural Sciences, Kagoshima University, Korimoto 1-21-24, Kagoshima, 890-0065, Japan.|Tropical Biosphere Research Center, University of the Ryukyus, Senbaru 1, Nishihara, Okinawa, 903-0213, Japan.
authors.forename: Ishmael
authors.initials: I
authors.lastname: Mutanda
authors.affiliation: Tropical Biosphere Research Center, University of the Ryukyus, Senbaru 1, Nishihara, Okinawa, 903-0213, Japan.
authors.forename: Masashi
authors.initials: M
authors.lastname: Inafuku
authors.affiliation: Tropical Biosphere Research Center, University of the Ryukyus, Senbaru 1, Nishihara, Okinawa, 903-0213, Japan.
authors.forename: Seikoh
authors.initials: S
authors.lastname: Saitoh
authors.affiliation: Tropical Biosphere Research Center, University of the Ryukyus, Senbaru 1, Nishihara, Okinawa, 903-0213, Japan.
authors.forename: Hironori
authors.initials: H
authors.lastname: Iwasaki
authors.affiliation: Graduate School of Agriculture, University of the Ryukyus, Senbaru 1, Nishihara, Okinawa, 903-0213, Japan.
authors.forename: Masakazu
authors.initials: M
authors.lastname: Fukuta
authors.affiliation: Department of Applied Biological Sciences, Saga University, Saga, 840-8502, Japan.
authors.forename: Keiichi
authors.initials: K
authors.lastname: Watanabe
authors.affiliation: Tropical Biosphere Research Center, University of the Ryukyus, Senbaru 1, Nishihara, Okinawa, 903-0213, Japan. okuhiros@comb.u-ryukyu.ac.jp.
authors.forename: Hirosuke
authors.initials: H
authors.lastname: Oku
mesh_terms: D002070:Butadienes / Q000378:metabolism*; D002940:Circadian Rhythm; D030681:Ficus / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D045782:Hemiterpenes / Q000378:metabolism*; D053858:Metabolic Networks and Pathways; D010420:Pentanes / Q000378:metabolism*; D010788:Photosynthesis; D010937:Plant Growth Regulators / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology; D017422:Sequence Analysis, DNA; D013312:Stress, Physiological; D013696:Temperature
chemical_list: D002070:Butadienes; D045782:Hemiterpenes; D010420:Pentanes; D010937:Plant Growth Regulators; D010940:Plant Proteins; C005059:isoprene
keywords: MEP pathway; cold; isoprene synthase; promoter; transcriptional regulation; transcriptome