title: Isoprene function in two contrasting poplars under salt and sunflecks.
abstract: In the present study, biogenic volatile organic compound (BVOC) emissions and photosynthetic gas exchange of salt-sensitive (Populus x canescens (Aiton) Sm.) and salt-tolerant (Populus euphratica Oliv.) isoprene-emitting and non-isoprene-emitting poplars were examined under controlled high-salinity and high-temperature and -light episode ('sunfleck') treatments. Combined treatment with salt and sunflecks led to an increased isoprene emission capacity in both poplar species, although the photosynthetic performance of P. × canescens was reduced. Indeed, different allocations of isoprene precursors between the cytosol and the chloroplast in the two species were uncovered by means of (13)CO2 labeling. Populus × canescens leaves, moreover, increased their use of 'alternative' carbon (C) sources in comparison with recently fixed C for isoprene biosynthesis under salinity. Our studies show, however, that isoprene itself does not have a function in poplar survival under salt stress: the non-isoprene-emitting leaves showed only a slightly decreased photosynthetic performance compared with wild type under salt treatment. Lipid composition analysis revealed differences in the double bond index between the isoprene-emitting and non-isoprene-emitting poplars. Four clear metabolomics patterns were recognized, reflecting systemic changes in flavonoids, sterols and C fixation metabolites due to the lack/presence of isoprene and the absence/presence of salt stress. The studies were complemented by long-term temperature stress experiments, which revealed the thermotolerance role of isoprene as the non-isoprene-emitting leaves collapsed under high temperature, releasing a burst of BVOCs. Engineered plants with a low isoprene emission potential might therefore not be capable of resisting high-temperature episodes.
authors.affiliation: Research Unit Environmental Simulation, Institute of Biochemical Plant Pathology, Helmholtz Zentrum München, 85764 Neuherberg, Germany.
authors.forename: K
authors.initials: K
authors.lastname: Behnke
authors.forename: A
authors.initials: A
authors.lastname: Ghirardo
authors.forename: D
authors.initials: D
authors.lastname: Janz
authors.forename: B
authors.initials: B
authors.lastname: Kanawati
authors.forename: J
authors.initials: J
authors.lastname: Esperschütz
authors.forename: I
authors.initials: I
authors.lastname: Zimmer
authors.forename: P
authors.initials: P
authors.lastname: Schmitt-Kopplin
authors.forename: Ü
authors.initials: Ü
authors.lastname: Niinemets
authors.forename: A
authors.initials: A
authors.lastname: Polle
authors.forename: J P
authors.initials: JP
authors.lastname: Schnitzler
authors.forename: M
authors.initials: M
authors.lastname: Rosenkranz
mesh_terms: D002070:Butadienes / Q000378:metabolism; D002244:Carbon / Q000378:metabolism*; D002245:Carbon Dioxide / Q000378:metabolism; D005419:Flavonoids / Q000235:genetics / Q000378:metabolism; D045782:Hemiterpenes / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism; D006358:Hot Temperature; D055442:Metabolome / Q000235:genetics; D010420:Pentanes / Q000378:metabolism; D010788:Photosynthesis / Q000235:genetics; D010840:Phytosterols / Q000235:genetics / Q000378:metabolism; D018515:Plant Leaves / Q000378:metabolism; D032107:Populus / Q000235:genetics* / Q000378:metabolism; D055049:Salt Tolerance / Q000235:genetics*; D012492:Salts / Q000378:metabolism / Q000494:pharmacology; D012965:Sodium Chloride / Q000009:adverse effects / Q000378:metabolism; D013045:Species Specificity; D013312:Stress, Physiological / Q000235:genetics*; D013472:Sunlight; D014197:Trees / Q000235:genetics / Q000378:metabolism; D055549:Volatile Organic Compounds / Q000378:metabolism
chemical_list: D002070:Butadienes; D005419:Flavonoids; D045782:Hemiterpenes; D010420:Pentanes; D010840:Phytosterols; D012492:Salts; D055549:Volatile Organic Compounds; C005059:isoprene; D002245:Carbon Dioxide; D012965:Sodium Chloride; D002244:Carbon
keywords: 13C labeling; Populus euphratica; Populus × canescens; isoprene; lipids; metabolomics; salt; thermotolerance