title: Spectacular Oscillations in Plant Isoprene Emission under Transient Conditions Explain the Enigmatic CO2 Response.
abstract: Plant isoprene emissions respond to light and temperature similarly to photosynthesis, but CO2dependencies of isoprene emission and photosynthesis are profoundly different, with photosynthesis increasing and isoprene emission decreasing with increasing CO2concentration due to reasons not yet understood. We studied isoprene emission, net assimilation rate, and chlorophyll fluorescence under different CO2and O2concentrations in the strong isoprene emitter hybrid aspen (Populus tremula × Populus tremuloides), and used rapid changes in ambient CO2or O2concentrations or light level to induce oscillations. As isoprene-emitting species support very high steady-state chloroplastic pool sizes of the primary isoprene substrate, dimethylallyl diphosphate (DMADP), which can mask the effects of oscillatory dynamics on isoprene emission, the size of the DMADP pool was experimentally reduced by either partial inhibition of isoprenoid synthesis pathway by fosmidomycin-feeding or by changes in ambient gas concentrations leading to DMADP pool depletion in intact leaves. In feedback-limited conditions observed at low O2and/or high CO2concentration under which the rate of photosynthesis is governed by the limited rate of ATP and NADPH formation due to low chloroplastic phosphate levels, oscillations in photosynthesis and isoprene emission were repeatedly induced by rapid environmental modifications in both partly fosmidomycin-inhibited leaves and in intact leaves with in vivo reduced DMADP pools. The oscillations in net assimilation rate and isoprene emission in feedback-inhibited leaves were in the same phase, and relative changes in the pools of photosynthetic metabolites and DMADP estimated by in vivo kinetic methods were directly proportional through all oscillations induced by different environmental perturbations. We conclude that the oscillations in isoprene emission provide direct experimental evidence demonstrating that the response of isoprene emission to changes in ambient gas concentrations is controlled by the chloroplastic reductant supply.
authors: Institute of Agricultural and Environmental Sciences, Estonian University of Life Sciences, 51014 Tartu, Estonia (B.R., E.T., Ü.N.).|Institute of Technology, University of Tartu, Tartu 50411, Estonia (B.R.); and.|Estonian Academy of Sciences, 10130 Tallinn, Estonia (Ü.N.).
authors: Bahtijor
authors: 0000-0001-5178-8617
authors: B
authors: Rasulov
authors: Institute of Agricultural and Environmental Sciences, Estonian University of Life Sciences, 51014 Tartu, Estonia (B.R., E.T., Ü.N.).|Institute of Technology, University of Tartu, Tartu 50411, Estonia (B.R.); and.|Estonian Academy of Sciences, 10130 Tallinn, Estonia (Ü.N.).
authors: Eero
authors: 0000-0002-8093-6444
authors: E
authors: Talts
authors: Institute of Agricultural and Environmental Sciences, Estonian University of Life Sciences, 51014 Tartu, Estonia (B.R., E.T., Ü.N.); ylo.niinemets@emu.ee.|Institute of Technology, University of Tartu, Tartu 50411, Estonia (B.R.); and ylo.niinemets@emu.ee.|Estonian Academy of Sciences, 10130 Tallinn, Estonia (Ü.N.) ylo.niinemets@emu.ee.
authors: Ülo
authors: 0000-0002-3078-2192
authors: Ü
authors: Niinemets
mesh_terms: D002070:Butadienes / Q000378:metabolism*; D002245:Carbon Dioxide / Q000494:pharmacology*; D002734:Chlorophyll / Q000378:metabolism; D005453:Fluorescence; D005578:Fosfomycin / Q000031:analogs & derivatives / Q000494:pharmacology; D045782:Hemiterpenes / Q000378:metabolism*; D007700:Kinetics; D008954:Models, Biological; D009943:Organophosphorus Compounds / Q000378:metabolism; D010420:Pentanes / Q000378:metabolism*; D010788:Photosynthesis / Q000187:drug effects; D018515:Plant Leaves / Q000187:drug effects / Q000378:metabolism; D032107:Populus / Q000187:drug effects / Q000378:metabolism*; D012274:Ribulosephosphates; D014835:Volatilization
chemical_list: D002070:Butadienes; D045782:Hemiterpenes; D009943:Organophosphorus Compounds; D010420:Pentanes; D012274:Ribulosephosphates; C005059:isoprene; D002734:Chlorophyll; D002245:Carbon Dioxide; C001933:ribulose-1,5 diphosphate; D005578:Fosfomycin; C043060:3,3-dimethylallyl pyrophosphate; C024640:fosmidomycin