chlorophyll-a and isoprene

This review focuses on the biosynthesis of pigments in the unicellular alga Chlamydomonas reinhardtii and their physiological and regulatory functions in the context of information gathered from studies of other photosynthetic organisms. C. reinhardtii is serving as an important model organism for studies of photosynthesis and the pigments associated with the photosynthetic apparatus. Despite extensive information pertaining to the biosynthetic pathways critical for making chlorophylls and carotenoids, we are just beginning to understand the control of these pathways, the coordination between pigment and apoprotein synthesis, and the interactions between the activities of these pathways and those for other important cellular metabolites branching from these pathways. Other exciting areas relating to pigment function are also emerging: the role of intermediates of pigment biosynthesis as messengers that coordinate metabolism in the chloroplast with nuclear gene activity, and the identification of photoreceptors and their participation in critical cellular processes including phototaxis, gametogenesis, and the biogenesis of the photosynthetic machinery. These areas of research have become especially attractive for intensive development with the application of potent molecular and genomic tools currently being applied to studies of C. reinhardtii.

Topics: Animals; Butadienes; Carotenoids; Cell Nucleus; Chlamydomonas reinhardtii; Chlorophyll; Chloroplasts; Cytochrome b6f Complex; Hemiterpenes; Isomerism; Light-Harvesting Protein Complexes; Lycopene; Models, Biological; Oxygen; Pentanes; Photoreceptor Cells, Invertebrate; Photosynthesis; Pigments, Biological; Plant Proteins; Protozoan Proteins; Rhodopsin

The aim of this work was to study the changes in the BVOCs emission rates and physiological mechanistic response of

Topics: Chlorophyll; Droughts; Monoterpenes; Pinus; Sesquiterpenes; Starch; Volatile Organic Compounds

Isoprene synthase converts dimethylallyl diphosphate to isoprene and appears to be necessary and sufficient to allow plants to emit isoprene at significant rates. Isoprene can protect plants from abiotic stress but is not produced naturally by all plants; for example, Arabidopsis (

Topics: Alkyl and Aryl Transferases; Arabidopsis; Butadienes; Carotenoids; Chlorophyll; Eucalyptus; Gene Expression Regulation, Plant; Hemiterpenes; Nicotiana; Photosynthesis; Plant Leaves; Signal Transduction; Stress, Physiological; Transformation, Genetic

At high temperatures, isoprene-emitting plants display a higher photosynthetic rate and a lower nonphotochemical quenching (NPQ) compared with nonemitting plants. The mechanism of this phenomenon, which may be very important under current climate warming, is still elusive. NPQ was dissected into its components, and chlorophyll fluorescence lifetime imaging microscopy (FLIM) was used to analyse the dynamics of excited chlorophyll relaxation in isoprene-emitting and nonemitting plants. Thylakoid membrane stiffness was also measured using atomic force microscope (AFM) to identify a possible mode of action of isoprene in improving photochemical efficiency and photosynthetic stability. We show that, when compared with nonemitters, isoprene-emitting tobacco plants exposed at high temperatures display a reduced increase of the NPQ energy-dependent component (qE) and stable (1) chlorophyll fluorescence lifetime; (2) amplitude of the fluorescence decay components; and (3) thylakoid membrane stiffness. Our study shows for the first time that isoprene maintains PSII stability at high temperatures by preventing the modifications of the surrounding environment, namely providing a more steady and homogeneous distribution of the light-absorbing centres and a stable thylakoid membrane stiffness. Isoprene photoprotects leaves with a mechanism alternative to NPQ, enabling plants to maintain a high photosynthetic rate at rising temperatures.

Topics: Butadienes; Chlorophyll; Chloroplasts; Fluorescence; Hemiterpenes; Hot Temperature; Nicotiana; Photosynthesis; Photosystem II Protein Complex; Plant Leaves; Protein Stability

Spatial distribution and sea-to-air flux of isoprene in the East China Sea and the South Yellow Sea in July 2013 were investigated. This study is the first to report the concentrations of isoprene in the China marginal seas. Isoprene concentrations in the surface seawater during summer ranged from 32.46 to 173.5 pM, with an average of 83.62 ± 29.22 pM. Distribution of isoprene in the study area was influenced by the diluted water from the Yangtze River, which stimulated higher in-situ phytoplankton production of isoprene rather than direct freshwater input. Variations in isoprene concentrations were found to be diurnal, with high values observed during daytime. A significant correlation was observed between isoprene and chlorophyll a in the study area. Relatively higher isoprene concentrations were recorded at stations where the phytoplankton biomass was dominated by Chaetoceros, Skeletonema, Pennate-nitzschia, and Thalassiosira. Positive correlation was observed between isoprene and methyl iodide. In addition, sea-to-air fluxes of isoprene approximately ranged from 22.17 nmol m

Topics: Air Pollutants; Biomass; Butadienes; China; Chlorophyll; Chlorophyll A; Hemiterpenes; Pentanes; Phytoplankton; Rivers; Seasons; Seawater; Water Pollutants, Chemical

Concentration- and flux-based O

Topics: Analysis of Variance; Butadienes; Chlorophyll; Clone Cells; Hemiterpenes; Ozone; Pentanes; Plant Leaves; Populus

The release of stress-driven volatiles throughout leaf development has been little studied. Therefore, we subjected poplar leaves during their developmental stage (from 2 days to 2 weeks old) to wounding by a single punch hole, and measured online the wound-induced volatile organic compound emissions. Our study shows that the emission of certain volatile compounds fades with increasing leaf age. Among these compounds we found lipoxygenase products (LOX products), acetaldehyde, methyl benzoate, methyl salicylate, and mono- and sesquiterpenes. In parallel, we studied the fading of constitutive emissions of methanol during leaf maturation, as well as the rise in isoprene constitutive emission during leaf maturation and its relationship to leaf photosynthetic capacity. We found highly significant relationships between leaf chlorophyll content, photosynthetic capacity, and leaf size during leaf ageing. As the level of constitutive defences increases with increasing leaf age, the strength of the volatile signal is expected to be gradually reduced. The higher elicitation of volatile organic compound emissions (especially LOX products) in younger leaves could be an evolutionary defence against herbivory, given that younger leaves are usually more subjected to infestation and herbivory.

Topics: Butadienes; Chlorophyll; Hemiterpenes; Herbivory; Lipoxygenase; Methanol; Pentanes; Photosynthesis; Plant Leaves; Populus; Time Factors; Volatile Organic Compounds

Physiological, biochemical and morpho-anatomical traits that determine the phenotypic plasticity of plants under drought were tested in two Arundinoideae with contrasting habitats, growth traits and metabolism: the fast-growing Arundo donax, which also is a strong isoprene emitter, and the slow-growing Hakonechloa macra that does not invest on isoprene biosynthesis. In control conditions, A. donax displayed not only higher photosynthesis but also higher concentration of carotenoids and lower phenylpropanoid content than H. macra. In drought-stressed plants, photosynthesis was similarly inhibited in both species, but substantially recovered only in A. donax after rewatering. Decline of photochemical and biochemical parameters, increased concentration of CO2 inside leaves, and impairment of chloroplast ultrastructure were only observed in H. macra indicating damage of photosynthetic machinery under drought. It is suggested that volatile and non-volatile isoprenoids produced by A. donax efficiently preserve the chloroplasts from transient drought damage, while H. macra invests on phenylpropanoids that are less efficient in preserving photosynthesis but likely offer better antioxidant protection under prolonged stress.

Topics: Abscisic Acid; Apigenin; Butadienes; Carotenoids; Chlorophyll; Chloroplasts; Coumaric Acids; Dehydration; Droughts; Ecosystem; Hemiterpenes; Luteolin; Pentanes; Photosynthesis; Poaceae; Water

Isoprene is a small lipophilic molecule with important functions in plant protection against abiotic stresses. Here, we studied the lipid composition of thylakoid membranes and chloroplast ultrastructure in isoprene-emitting (IE) and nonisoprene-emitting (NE) poplar (Populus × canescens). We demonstrated that the total amount of monogalactosyldiacylglycerols, digalactosyldiacylglycerols, phospholipids, and fatty acids is reduced in chloroplasts when isoprene biosynthesis is blocked. A significantly lower amount of unsaturated fatty acids, particularly linolenic acid in NE chloroplasts, was associated with the reduced fluidity of thylakoid membranes, which in turn negatively affects photosystem II photochemical efficiency. The low photosystem II photochemical efficiency in NE plants was negatively correlated with nonphotochemical quenching and the energy-dependent component of nonphotochemical quenching. Transmission electron microscopy revealed alterations in the chloroplast ultrastructure in NE compared with IE plants. NE chloroplasts were more rounded and contained fewer grana stacks and longer stroma thylakoids, more plastoglobules, and larger associative zones between chloroplasts and mitochondria. These results strongly support the idea that in IE species, the function of this molecule is closely associated with the structural organization and functioning of plastidic membranes.

Topics: Butadienes; Chlorophyll; Fatty Acids; Fluorescence; Gene Knockdown Techniques; Hemiterpenes; Least-Squares Analysis; Lipids; Malondialdehyde; Models, Biological; Multivariate Analysis; Oxidation-Reduction; Pentanes; Photosynthesis; Photosystem II Protein Complex; Plant Proteins; Populus; Thylakoids

Isoprene-emitting plants are better protected against thermal and oxidative stresses. Isoprene may strengthen membranes avoiding their denaturation and may quench reactive oxygen and nitrogen species, achieving a similar protective effect. The physiological role of isoprene in unstressed plants, up to now, is not understood. It is shown here, by monitoring the non-photochemical quenching (NPQ) of chlorophyll fluorescence of leaves with chemically or genetically altered isoprene biosynthesis, that chloroplasts of isoprene-emitting leaves dissipate less energy as heat than chloroplasts of non-emitting leaves, when exposed to physiologically high temperatures (28-37 °C) that do not impair the photosynthetic apparatus. The effect was especially remarkable at foliar temperatures between 30 °C and 35 °C, at which isoprene emission is maximized and NPQ is quenched by about 20%. Isoprene may also allow better stability of photosynthetic membranes and a more efficient electron transfer through PSII at physiological temperatures, explaining most of the NPQ reduction and the slightly higher photochemical quenching that was also observed in isoprene-emitting leaves. The possibility that isoprene emission helps in removing thermal energy at the thylakoid level is also put forward, although such an effect was calculated to be minimal. These experiments expand current evidence that isoprene is an important trait against thermal and oxidative stresses and also explains why plants invest resources in isoprene under unstressed conditions. By improving PSII efficiency and reducing the need for heat dissipation in photosynthetic membranes, isoprene emitters are best fitted to physiologically high temperatures and will have an evolutionary advantage when adapting to a warming climate.

Topics: Arabidopsis; Butadienes; Carbon Dioxide; Chlorophyll; Chloroplasts; Electron Transport; Hemiterpenes; Hot Temperature; Nicotiana; Pentanes; Photosynthesis; Plant Leaves; Populus; Stress, Physiological

Hybrid poplar (Populus × canadensis) saplings were subjected to acute ultraviolet-A (UV-A) irradiation (30 W m(-2) , ambient treatment, 60, 90 and 120 W m(-2) of UV-A irradiance) to determine the effects on photosynthesis and biogenic volatile organic compound (BVOC) emissions in two different short-term experiments (i.e. sequential increase in UV-A irradiance and UV-A intensity-response relationships). Both intensity-response experiments showed that the UV-A ambient treatment did not affect photosynthesis and BVOC emissions. Whereas exposition at 60, 90 and 120 W m(-2) of UV-A (first experiment), increasingly inhibited photosynthesis. This increasing inhibition was also detected by decreasing trends of both photochemical reflectance index (PRI) and fluorescence yield. Isoprene emission resulted to be very sensitive to increasing UV-A irradiances. Methanol was also very sensitive to high UV-A radiation, suggesting the occurrence of strong damages of cellular structures. The second experiment, which was performed both in the middle of July and repeated towards the end of the summer, showed a temporal variations in the UV-A intensity-response relationships. In fact, there were no longer significant differences in photosynthesis, PRI and isoprene emission in response to high UV-A radiation toward the end of the summer season. The adaxial flavonoid level increased significantly over the period monitored, resulting 85% higher toward the end of the summer than during the middle of the summer. This dramatic increase in the adaxial flavonoids may have played a protective role against UV-A radiation by shielding leaves. Our findings add to the understanding of physiological processes involved in plant response to UV radiation.

Topics: Acetaldehyde; Butadienes; Carbon; Chlorophyll; Flavonoids; Hemiterpenes; Methanol; Pentanes; Photosynthesis; Populus; Seasons; Ultraviolet Rays; Volatile Organic Compounds

In higher plants, many isoprenoids are synthesised via the chloroplastic 1-deoxy-D-xylulose 5-phosphate/2-C-methyl-D-erythritol 4-phosphate (MEP) pathway. Attempts to elucidate the function of individual isoprenoids have used the antibiotic/herbicidal compound fosmidomycin (3-[N-formyl-N-hydroxy amino] propyl phosphonic acid) to inhibit this pathway. Examination of the effect of fosmidomycin on the major components of photosynthesis in leaves of white poplar (Populus alba) and tobacco (Nicotiana tabacum) was made. Fosmidomycin reduced net photosynthesis in both species within 1 h of application, but only when photosynthesis was light-saturated. In P. alba, these reductions were confounded by high light and fosmidomycin inducing stomatal patchiness. In tobacco, this was caused by significant reductions in PSII chlorophyll fluorescence and reductions in V(cmax) and J(max). Our data indicate that the diminution of photosynthesis is likely a complex effect resulting from the inhibition of multiple MEP pathway products, resulting in photoinhibition and photo-damage. These effects should be accounted for in experimental design and analysis when using fosmidomycin to avoid misinterpretation of results as measured by gas exchange and chlorophyll fluorescence.

Topics: Butadienes; Carbon Dioxide; Chlorophyll; Fluorescence; Fosfomycin; Hemiterpenes; Herbicides; Nicotiana; Pentanes; Photosynthesis; Plant Leaves; Plant Stomata; Populus; Terpenes

Natural polyisoprene is a biopolymer consisting of isoprene units (C(5)H(8)) that is used commercially in household, medical, and industrial materials. For the management of natural polyisoprene production, the selection of high-yield polyisoprene-producing trees, and an understanding of polyisoprene biosynthesis, a high-throughput and highly sensitive screening method for the quantification of polyisoprene is required. In this study, we examined pyrolysates from polyisoprenes, polyprenols, carotenoids, ubiquinone (CoQ-10), and sterols by pyrolysis gas chromatography/mass spectrometry (PyGC/MS) and determined that the amounts of isoprene and limonene released from polyprenols and polyisoprenes were dependent upon their molecular weights. Based on these results, we developed a relative quantification method for polyisoprene in leaves by direct analysis of 1 mg of leaves using PyGC/MS. This novel quantification method eliminated extraction steps and can be used in the measurement of polyisoprene contents in Eucommia ulmoides and Hevea brasiliensis.

Topics: Benzoquinones; Butadienes; Carotenoids; Chlorophyll; Cyclohexenes; Eucommiaceae; Gas Chromatography-Mass Spectrometry; Hemiterpenes; Hevea; High-Throughput Screening Assays; Latex; Limonene; Molecular Weight; Pentanes; Sterols; Terpenes

Isoprene synthase (ISPS) catalyzes the formation of isoprene, an important volatile terpenoid with strong effects on global atmospheric chemistry and protective physiological functions in plant leaves. Many terpene synthase genes including isoprene synthase, a member of the TPS-b cluster of this numerous gene family, were already functionally analysed but much less is known about regulation of their promoters. To study regulation of the PcISPS gene in detail we developed transgenic Grey poplar (Populus x canescens) and Arabidopsis thaliana plants in which the PcISPS promoter is fused to enhanced green fluorescent protein (E-GFP) and beta-glucuronidase (GUS) reporter genes. We analysed these reporters during plant development, for organ specificity and in plants subjected to different light and temperature regimes. We observed low promoter activity in non-isoprene emitting tissue like roots where ISPS gene is transcribed but no active enzyme is detectable. In leaves we demonstrate that light and temperature directly modulate ISPS promoter activity. Moreover, with confocal laser scanning microscopy we show a cell specific gradient of ISPS promoter activity within the leaf parenchyma depending on light direction. Our results indicate that ISPS promoter activity, which correlates with basal isoprene emission capacity, is not uniformly distributed within leaf tissue and that it can adapt rapidly towards internal as well as external environmental stimuli.

Topics: Alkyl and Aryl Transferases; Arabidopsis; Butadienes; Chlorophyll; Environment; Fluorescence; Gene Expression Profiling; Gene Expression Regulation, Developmental; Gene Expression Regulation, Plant; Glucuronidase; Green Fluorescent Proteins; Hemiterpenes; Light; Organ Specificity; Pentanes; Plant Leaves; Plant Roots; Populus; Promoter Regions, Genetic; Temperature

This study examined whether two genotypes of hybrid poplar (Populus deltoides x Populus trichocarpa), previously classified as ozone tolerant and ozone sensitive, had differing physiological and biochemical responses when fumigated with 120 nL L(-1) ozone for 6 h per day for eight consecutive days. Isoprene emission rate, ozone uptake and a number of physiological and biochemical parameters were investigated before, during and after fumigation with ozone. Previous studies have shown that isoprene protects plants against oxidative stress. Therefore, it was hypothesized that these two genotypes would differ in either their basal isoprene emission rates or in the response of isoprene to fumigation by ozone. Our results showed that the basal emission rates of isoprene, physiological responses and ozone uptake rates were all similar. However, significant differences were found in visible damage, carotenoids, hydrogen peroxide (H(2)O(2)), thiobarbituric acid reactions (TBARS) and post-fumigation isoprene emission rates. It is shown that, although the classification of ozone tolerance or sensitivity had been previously clearly and carefully defined using one particular set of parameters, assessment of other key variables does not necessarily lead to the same conclusions. Thus, it may be necessary to reconsider the way in which plants are classified as ozone tolerant or sensitive.

Topics: Ascorbic Acid; Butadienes; Carotenoids; Chlorophyll; Chlorophyll A; Genotype; Hemiterpenes; Hydrogen Peroxide; Lipid Peroxidation; Oxidative Stress; Ozone; Pentanes; Plant Leaves; Populus; Thiobarbiturates

The physiological role of isoprene emission in plants is a matter of much debate. One of the most widely propagated hypotheses suggests a function of isoprene in the protection of leaf physiological processes against thermal and oxidative stress. To test this hypothesis, we developed transgenic Grey poplar (Populusxcanescens) plants in which gene expression of isoprene synthase (ISPS) was either silenced by RNA interference (RNAi) or upregulated by over-expression of the ISPS gene. Despite increased ISPS mRNA levels, we did not observe consistent increases in isoprene emission in the over-expressing lines, indicating post-transcriptional control of ISPS by co-suppression. In the RNAi lines, levels of isoprene emission were effectively suppressed to virtually zero. Transgenic plants were subjected to temperature stress with three transient heat phases of 38-40 degrees C, each followed by phases of recovery at 30 degrees C. Parallel measurements of gas exchange, chlorophyll fluorescence and isoprene emission provided new insights into the physiological link between isoprene and enhanced temperature tolerance. Transgenic non-isoprene-emitting poplars showed reduced rates of net assimilation and photosynthetic electron transport during heat stress, but not in the absence of stress. The decrease in the efficiency of photochemistry was inversely correlated with the increase in heat dissipation of absorbed light energy, measured as NPQ (non-photochemical quenching). Isoprene-repressed poplars also displayed an increased formation of the xanthophyll cycle pigment zeaxanthin in the absence of stress, which can cause increased NPQ or may indicate an increased requirement for antioxidants. In conclusion, using a molecular genetic approach, we show that down-regulation of isoprene emission affects thermotolerance of photosynthesis and induces increased energy dissipation by NPQ pathways.

Topics: Acclimatization; Alkyl and Aryl Transferases; Butadienes; Carbon Dioxide; Chlorophyll; Electron Transport; Hemiterpenes; Hot Temperature; Organophosphorus Compounds; Pentanes; Photosynthesis; Pigments, Biological; Plants, Genetically Modified; Populus; RNA Interference

The effect of ocean biological productivity on marine clouds is explored over a large phytoplankton bloom in the Southern Ocean with the use of remotely sensed data. Cloud droplet number concentration over the bloom was twice what it was away from the bloom, and cloud effective radius was reduced by 30%. The resulting change in the short-wave radiative flux at the top of the atmosphere was -15 watts per square meter, comparable to the aerosol indirect effect over highly polluted regions. This observed impact of phytoplankton on clouds is attributed to changes in the size distribution and chemical composition of cloud condensation nuclei. We propose that secondary organic aerosol, formed from the oxidation of phytoplankton-produced isoprene, can affect chemical composition of marine cloud condensation nuclei and influence cloud droplet number. Model simulations support this hypothesis, indicating that 100% of the observed changes in cloud properties can be attributed to the isoprene secondary organic aerosol.

Topics: Aerosols; Atmosphere; Butadienes; Chlorophyll; Chlorophyll A; Hemiterpenes; Oceans and Seas; Oxidation-Reduction; Pentanes; Phytoplankton; Weather; Wind

Two plant test systems are presented in the search for new inhibitors of the non-mevalonate isoprenoid pathway. A derivative of clomazone appears to be an inhibitor of the deoxyxylulose 5-phosphate/methylerythritol 4-phosphate (DOXP/MEP) pathway of isoprenoid formation.

Topics: Anti-Bacterial Agents; Antimalarials; Bacteria; Butadienes; Carotenoids; Chlorophyll; Drug Evaluation, Preclinical; Hemiterpenes; Herbicides; Hordeum; Isoxazoles; Oxazolidinones; Pentanes; Plant Leaves; Plants