title: Isoprene production in transgenic tobacco alters isoprenoid, non-structural carbohydrate and phenylpropanoid metabolism, and protects photosynthesis from drought stress.
abstract: Isoprene strengthens thylakoid membranes and scavenges stress-induced oxidative species. The idea that isoprene production might also influence isoprenoid and phenylpropanoid pathways under stress conditions was tested. We used transgenic tobacco to compare physiological and biochemical traits of isoprene-emitting (IE) and non-emitting (NE) plants exposed to severe drought and subsequent re-watering. Photosynthesis was less affected by drought in IE than in NE plants, and higher rates were also observed in IE than in NE plants recovering from drought. Isoprene emission was stimulated by mild drought. Under severe drought, isoprene emission declined, and levels of non-volatile isoprenoids, specifically de-epoxidated xanthophylls and abscisic acid (ABA), were higher in IE than in NE plants. Soluble sugars and phenylpropanoids were also higher in IE plants. After re-watering, IE plants maintained higher levels of metabolites, but isoprene emission was again higher than in unstressed plants. We suggest that isoprene production in transgenic tobacco triggered different responses, depending upon drought severity. Under drought, the observed trade-off between isoprene and non-volatile isoprenoids suggests that in IE plants isoprene acts as a short-term protectant, whereas non-volatile isoprenoids protect against severe, long-term damage. After drought, it is suggested that the capacity to emit isoprene might up-regulate production of non-volatile isoprenoids and phenylpropanoids, which may further protect IE leaves.
authors.affiliation: Institute for Plant Protection, Department of Biology, Agriculture and Food Sciences, The National Research Council of Italy (CNR), I-50019, Sesto Fiorentino (Florence), Italy.
authors.forename: Massimiliano
authors.initials: M
authors.lastname: Tattini
authors.forename: Violeta
authors.initials: V
authors.lastname: Velikova
authors.forename: Claudia
authors.initials: C
authors.lastname: Vickers
authors.forename: Cecilia
authors.initials: C
authors.lastname: Brunetti
authors.forename: Martina
authors.initials: M
authors.lastname: Di Ferdinando
authors.forename: Alice
authors.initials: A
authors.lastname: Trivellini
authors.forename: Silvia
authors.initials: S
authors.lastname: Fineschi
authors.forename: Giovanni
authors.initials: G
authors.lastname: Agati
authors.forename: Francesco
authors.initials: F
authors.lastname: Ferrini
authors.forename: Francesco
authors.initials: F
authors.lastname: Loreto
mesh_terms: D000040:Abscisic Acid / Q000378:metabolism; D002070:Butadienes; D050260:Carbohydrate Metabolism; D055864:Droughts; D045782:Hemiterpenes / Q000096:biosynthesis*; D010420:Pentanes; D010788:Photosynthesis / Q000502:physiology*; D030821:Plants, Genetically Modified / Q000502:physiology; D013312:Stress, Physiological; D013729:Terpenes / Q000378:metabolism*; D014026:Nicotiana / Q000235:genetics / Q000502:physiology*; D024341:Xanthophylls / Q000378:metabolism
chemical_list: D002070:Butadienes; D045782:Hemiterpenes; D010420:Pentanes; D013729:Terpenes; D024341:Xanthophylls; C005059:isoprene; D000040:Abscisic Acid
keywords: MEP pathway; abscisic acid (ABA); carotenoids; flavonols; hexoses signalling; xanthophylls