Phytyl Side Chain Of Chlorophyll Research Articles

Use of Gas Chromatography-Mass Spectrometry Techniques (GC-MS, GC-MS/MS and GC-QTOF) for the Characterization of Photooxidation and Autoxidation Products of Lipids of Autotrophic Organisms in Environmental Samples.

This paper reviews applications of gas chromatography-mass spectrometry techniques for the characterization of photooxidation and autoxidation products of lipids of senescent phototrophic organisms. Particular attention is given to: (i) the selection of oxidation products that are sufficiently stable under environmental conditions and specific to each lipid class and degradation route; (ii) the description of electron ionization mass fragmentation of trimethylsilyl derivatives of these compounds; and (iii) the use of specific fragment ions for monitoring the oxidation of the main unsaturated lipid components of phototrophs. The techniques best geared for this task were gas chromatography-quadrupole-time of flight to monitor fragment ions with very high resolution and accuracy, and gas chromatography-tandem mass spectrometry to monitor very selective transitions in multiple reaction monitoring mode. The extent of the degradation processes can only be estimated if the oxidation products are unaffected by fast secondary oxidation reactions, as it is notably the case of ∆5-sterols, monounsaturated fatty acids, chlorophyll phytyl side-chain, and di- and triterpenoids. In contrast, the primary degradation products of highly branched isoprenoid alkenes possessing more than one trisubstituted double bond, alkenones, carotenoids and polyunsaturated fatty acids, appear to be too unstable with respect to secondary oxidation or other reactions to serve for quantification in environmental samples.

Seasonal monitoring of lipid degradation processes in the western English Channel links bacterial 10S-DOX enzyme activity to free fatty acid production by phytoplankton

In a few recent studies, the action of a bacterial dioxygenase (10S-DOX) on palmitoleic acid was observed within some polar and estuarine settings. To add further mechanistic information regarding the action of this enzyme in marine settings, we measured a range of lipids (sterols, fatty acids and the chlorophyll phytyl side chain) and their biotic and abiotic degradation products in water samples collected in 2018 from two depths (5 m and 25 m) at the temperate oceanographic time series site L4, located in the western English Channel. Lipid distributions indicated a dominance of diatoms and copepods during the spring bloom, while a peak in dinoflagellate activity was evident in samples collected from late summer/autumn, both outcomes being consistent with taxonomic data reported previously for the same sampling site and interval. Monitoring of lipid oxidation products characteristic of different degradation pathways showed a relatively weak effect of photo- and autoxidation processes, with these acting mainly on the more reactive lipids (i.e. chlorophyll and polyunsaturated fatty acids). In contrast, monitoring of biotic degradation processes revealed significant quantities of 10S-hydroxyhexadec-8(E)-enoic acid in samples collected at the end of April (reaching 40% of the residual parent palmitoleic acid), attributed to the involvement of bacterial 10-dioxygenase (10S-DOX) activity during the spring bloom. We propose that this enzyme could be utilised by bacteria to detoxify free fatty acids released by wounded diatoms in the presence of copepods

A lil3 chlp double mutant with exclusive accumulation of geranylgeranyl chlorophyll displays a lethal phenotype in rice

BackgroundPhytyl residues are the common side chains of chlorophyll (Chl) and tocopherols. Geranylgeranyl reductase (GGR), which is encoded by CHLP gene, is responsible for phytyl biosynthesis. The light-harvesting like protein LIL3 was suggested to be required for stability of GGR and protochlorophyllide oxidoreductase in Arabidopsis.ResultsIn this study, we isolated a yellow-green leaf mutant, 637ys, in rice (Oryza sativa). The mutant accumulated majority of Chls with unsaturated geranylgeraniol side chains and displayed a yellow-green leaf phenotype through the whole growth period. The development of chloroplasts was suppressed, and the major agronomic traits, especially No. of productive panicles per plant and of spikelets per panicle, dramatically decreased in 637ys. Besides, the mutant exhibited to be sensitive to light intensity and deficiency of tocopherols without obvious alteration in tocotrienols in leaves and grains. Map-based cloning and complementation experiment demonstrated that a point mutation on the OsLIL3 gene accounted for the mutant phenotype of 637ys. OsLIL3 is mainly expressed in green tissues, and its encoded protein is targeted to the chloroplast. Furthermore, the 637ys 502ys (lil3 chlp) double mutant exclusively accumulated geranylgeranyl Chl and exhibited lethality at the three-leaf stage.ConclusionsWe identified the OsLIL3 gene through a map-based cloning approach. Meanwhile, we demonstrated that OsLIL3 is of extreme importance to the function of OsGGR, and that the complete replacement of phytyl side chain of chlorophyll by geranylgeranyl chain could be fatal to plant survival in rice.

Monitoring abiotic degradation in sinking versus suspended Arctic sea ice algae during a spring ice melt using specific lipid oxidation tracers

The abiotic degradation state of sea ice algae released during a late spring ice melt process was determined by sampling the underlying waters and measuring certain well-known algal lipids and their oxidation products, including those derived from epi-brassicasterol, 24-methylenecholesterol, palmitoleic acid and the phytyl side-chain of chlorophyll. More specifically, parent lipids and some of their oxidation products were quantified in suspended (collected by filtration) and sinking (collected with sediment traps at 5 and 30m) particles from Resolute Passage (Canada) during a period of spring ice melt in 2012 and the outcomes compared with those obtained from related sea ice samples analyzed previously. Our data show that suspended cells in the near surface waters appeared to be only very weakly affected by photooxidative processes, likely indicative of a community of unaggregated living cells with high seeding potential for further growth. In contrast, we attribute the strong photooxidation state of the organic matter in the sediment traps deployed at 5m to the presence of senescent and somewhat aggregated sea ice algae that descended only relatively slowly within the euphotic zone, and was thus susceptible to photochemical degradation. On the other hand, the increased abiotic preservation of the sinking material collected in the sediment traps deployed at 30m, likely reflected more highly aggregated senescent sea ice algae that settled sufficiently rapidly out of the euphotic zone to avoid significant photooxidation. This better-preserved sinking material in the deeper sediment traps may therefore contribute more strongly to the underlying sediments. A three-component conceptual scheme summarizing the abiotic behavior of Arctic sea ice algae in underlying waters is proposed.

Autoxidation of chlorophyll phytyl side chain in senescent phototrophic organisms: A potential source of isophytol in the environment

In this short paper, it is demonstrated that autoxidation (free radical induced oxidation) of the chlorophyll phytyl side chain in senescent phytoplanktonic cells and higher plants constitutes a potential source of isophytol (3,7,11,15-tetramethylhexadec-1-en-3-ol) in the environment. To explain the formation of this isoprenoid alcohol, mechanisms involving the formation of the precursor 3-peroxy-3,7,11,15-tetramethylhexadec-1-ene are proposed.

Sequential photo- and autoxidation of diatom lipids in Arctic sea ice

We measured the concentrations of selected lipids and some of their degradation products in a time series of sea ice samples collected from Resolute Bay in the Canadian Arctic in 2012. The identification of specific tracers of photo- and autoxidation reactions provided evidence of both abiotic processes acting on organic matter, although none of the lipids appeared sensitive to significant biodegradation. Some differences in lipid reactivity were observed between the upper (3–10cm) and lower (0–3cm) sections of the cores, possibly as a result of increased exchange at the ice–water boundary for the latter. In terms of photodegradation, the phytyl side chain of chlorophyll and a tri-unsaturated highly branched isoprenoid (HBI) alkene were most affected, 24-methylenecholesterol (from diatoms) was more susceptible to photodegradation than brassicasterol (from diatoms and prymnesiophytes), while sitosterol and cholesterol, likely from a range of sources, were largely unaffected. With respect to autoxidation, the reactivity trend for the sterols was reversed, with significant autoxidation of sitosterol and cholesterol, but not of 24-methylenecholesterol or brassicasterol. The phytyl side chain of chlorophyll and a highly branched isoprenoid triene were also particularly susceptible to autoxidation. In contrast, the diatom fatty acid, C16:1, was not substantially altered by any degradation pathway. By measuring temporal changes in the proportions of specific tracers of each degradation process, we provide evidence that such abiotic reactions take place via sequential photooxidation and autoxidation, with homolytic cleavage of photochemically produced hydroperoxides leading to autoxidation of initial substrates and subsequent oxidation products. The observation of significant abiotic degradation of several lipids appears to take place despite the low temperature in sea ice (ca. 0°C) and should be considered carefully alongside other removal processes involving organic matter in marine systems.

Autoxidative and Photooxidative Reactivity of Highly Branched Isoprenoid (HBI) Alkenes

Autoxidation of several mono-, di-, tri- and tetra-unsaturated highly branched isoprenoid (HBI) alkenes was induced in organic solvents using a radical initiator and enhancer, and their degradation rates were compared to those of classical phytoplanktonic lipids (mono-unsaturated fatty acids, sterols and chlorophyll phytyl side-chain). Autoxidation of two HBI trienes was also investigated in senescent and highly photodegraded diatom cells, collected in the Antarctic, using Fe(2+) ions as radical inducers. Autoxidation rates of HBI alkenes were found to increase with the number of tri-substituted double bonds, as expected. Further, HBI trienes possessing one bis-allylic position (where hydrogen abstraction is highly favoured) were found to be particularly reactive towards autoxidation and degraded at similar rates compared to polyunsaturated fatty acids in diatom cells. By comparison of the autoxidation products of the most reactive tri-unsaturated HBI with the corresponding photooxidation products, some specific tracers of these two types of abiotic degradation processes were identified. The lack of reactivity of the mono-unsaturated HBI IP25 and a structurally similar di-unsaturated HBI towards autoxidative degradation supports the good preservation of these biomarkers in marine sediments.

Production of pristane and phytane in the marine environment: role of prokaryotes

This paper reviews studies dealing with the formation of pristane and phytane in the marine environment and focuses on the role played by prokaryotes in these processes. Prokaryotes may notably: (i) contribute to the formation of pristane during invertebrate feeding; (ii) hydrogenate isomeric pristenes and phytenes arising from degradation of the chlorophyll phytyl side-chain and/or α-tocopherol (vitamin E) to pristane and phytane, respectively; and (iii) convert trimeric oxidation products of α-tocopherol (produced abiotically in the water column and in the oxic zone of sediments) to pristane. Moreover, thermal maturation of isoprenoid components of archaea (isopranyl glyceryl ethers) also constitutes another potential source of pristane and phytane in thermally mature sediments. Prokaryotes thus appear to play a key role in formation of these isoprenoid alkanes in the marine environment.

Comparative study of UV and visible light induced degradation of lipids in non-axenic senescent cells of Emiliania huxleyi

Irradiation of killed non-axenic cells of Emiliania huxleyi (Prymnesiophyceae) by PAR and UVR resulted in a strong photodegradation of most of the unsaturated lipid components (chlorophylls, unsaturated fatty acids and brassicasterol) of this haptophyte. This degradation, which mainly involves type II (i.e. singlet oxygen-mediated) photosensitized oxidation processes, was induced by both PAR and UVR. Alkenones were the sole unsaturated components of E. huxleyi unaffected by photodegradation processes. This particular recalcitrance was attributed to the trans configuration of their double bonds, which is less reactive toward singlet oxygen than the classical cis configuration of the double bonds of the other lipids. UVR exposure also induced photosensitized stereomutation ( cis-trans isomerization) of the double bonds of some lipids (e.g. monounsaturated fatty acids and chlorophyll phytyl side-chain) and of some of their oxidation products affording (after reduction) some compounds (e.g. 9-hydroxyoctadec- cis-10-enoic and 10-hydroxyoctadec- cis-8-enoic acids arising from oleic acid oxidation and 11-hydroxyoctadec- cis-12-enoic and 12-hydroxyoctadec- cis-10-enoic acids arising from cis-vaccenic acid oxidation) sufficiently specific to act as tracers of UVR-induced photodegradation in situ. A strong photodegradation of specific bacterial monounsaturated fatty acids (e.g. cis-vaccenic and 11-MeC 18:1ω12 acids) was also observed and attributed to the migration of singlet oxygen from phytodetritus to the attached heterotrophic bacteria.

Free radical oxidation (autoxidation) of alkenones and other microalgal lipids in seawater

The free radical oxidation (autoxidation) of long chain alkenones derived from haptophyte microalgae was studied in the laboratory in the presence of a radical initiator (di- tert-butyl nitroxide) and a radical enhancer ( tert-butyl hydroperoxide). Alkenones were autoxidized faster than analogues of other common marine lipids such as phytyl acetate, methyl oleate and cholesteryl acetate. Alkenone autoxidation rates increased in an approximately linear fashion with the number of double bonds present in the molecule and so autoxidation has the potential to affect values of U 37 K ′ . The process seems to involve allylic hydrogen abstraction and subsequent oxidation of the allylic radical to form products that can be analysed as alkene polyols after NaBH 4 reduction. Evidence for the autoxidation of lipids in seawater was obtained from analysis of organic matter in sediment traps deployed at the DYFAMED site in the northwestern Mediterranean Sea. High contents of specific autoxidation products of monounsaturated fatty acids and the chlorophyll phytyl side chain were recognized in samples collected during post-bloom conditions, but not during a phytoplankton bloom event. Biomarkers for autoxidation include the presence of 8- and 11-hydroxyoctadec- cis-9-enoic acids and various phytol diols and triols. These same samples also showed anomalously high U 37 K ′ values (equivalent to an inferred temperature change of at least 2 °C), consistent with the results of the autoxidation experiments, but opposite to that expected for any effect due to nutrient limitation on haptophyte cells. Our work demonstrates that autoxidation of lipids may occur in seawater and that this has the potential to affect alkenone distributions, especially where residence times of particles are long. In such circumstances this might lead to a warm bias in estimates of palaeotemperature derived from alkenone ratios in sediments.

One-year seasonal survey of the chlorophyll photodegradation process in the northwestern Mediterranean Sea

Abstract Particulate samples from the water column were collected monthly from depths of 5–150 m, between May 1996 and March 1997, in the northwestern Mediterranean Sea (Ligurian Sea) as part of the DYFAMED project within the French JGOFS program. These samples were analyzed by gas chromatography-electron impact mass spectrometry for their phytol and 3-methylidene-3,7,11-trimethylhexadecan-1,2-diol (phytyldiol) content. The corresponding Chlorophyll Phytyl side chain Photodegradation Index, molar ratio of phytyldiol to phytol, was calculated and the mean amount of chlorophyll photodegraded within the euphotic zone estimated. Seasonal differences in the chlorophyll photodegradation process appear in the one-year study. The chlorophyll appeared more photodegraded in the surface water (generally more than 40% photodegraded at 5–10 m) than at the deep chlorophyll maximum (DCM) (40–50 m) observed in the summer stratified waters (about 20% photodegraded). This difference was attributed to the healthy state of the phytoplankton community (coincidence with the highest primary production levels) and to the lower intensity of irradiance at the DCM level. On the other hand, the bulk of the detrital chlorophyll (chlorophyll associated with phytodetritus, phaeopigments) undergoes photodegradation before it sinks out of the photic zone. However, in January (winter mixed water) the pigments exported towards the sea floor were less photodegraded. This is thought to result from a shorter period of residence of the pigments in the photic zone due to vertical convection and grazing activity of macrozooplankton (salps), which are producers of rapid sinking fecal pellets.

Labeling Patterns of Chloroplastidic Isoprenoids in Cultured Cells of Liverwort Ptychanthus striatus

Incorporation studies administering 2H- and 13C-labeled mevalonate (MVA) and 13C-labeled glucose to suspension cultured cells of the liverwort, Ptychanthus striatus, were carried out in order to examine the biosynthesis of the phytyl side-chain of chlorophyll a. Administration of 13C- and 2H-labeled MVA provided evidence for the involvement of the MVA pathway in the phytyl side-chain biosynthesis and preferential labeling of the farnesyl diphosphate (FPP)-derived portion. An alternate labeling pattern in the phytyl side-chain was observed which was slightly different to the non-equivalent labeling in other liverworts, such as Heteroscyphus planus and Lophocolea heterophylla and in the hornwort, Anthoceros punctatus. The labeling pattern observed after the administration of 13C-labeled glucose revealed the simultaneous involvement of the non-MVA pathway in the phytol biosynthesis of P. striatus cells.

Nonequivalent labeling of the phytyl side chain of chlorophyll a in callus of the hornwort Anthoceros punctatus.

Callus cultures of the hornwort Anthoceros punctatus were induced from the apical portions of the gametophytes. Calli can accumulate rosmarinic acid, which is suggested as an intermediate for anthocerotonic acid, a rare phenylpropanoid dimer with a cyclobutane ring, indicating that calli possess the ability to produce secondary metabolites found primarily in intact plants. Biosynthesis of chloroplastidic terpenoids of liverworts showed preferential labeling of the farnesyl diphosphate (FPP)-derived portion in the phytyl side chain of chlorophyll a (1) when calli of A. punctatus are incubated with (2)H- and (13)C-labeled mevalonate. This finding suggests either that cytoplasmic FPP (or isopentenyl diphosphate, IPP) is taken into chloroplasts and condensed with endogenous IPP derived from a nonmevalonate pathway, or that FPP is synthesized within chloroplasts from extraplastidically formed IPP (or mevalonate) and then condensed with endogenous IPP in a different subplastidic fraction.

Can a high chlorophyllase activity bias the use of the phytyldiol versus phytol ratio (CPPI) for the monitoring of chlorophyll photooxidation in seawater?

The photodegradation rates of chlorophyll-a and phytol in both its esterified and free forms were followed in killed cells of Phaeodactylum tricornutum Bohlin, a diatom possessing a strong chlorophyllase activity. The Chlorophyll Phytyl side chain Photodegradation Index (CPPI), defined as the molar ratio of phytyldiol (a specific photoproduct of the phytyl chain) versus phytol, was used to estimate the chlorophyll-a photodegradation rate. Despite the strong chlorophyllase activity of this alga and the high photoreactivity of free phytol, the CPPI gave a good estimation of the chlorophyll-a photodegradation state. These estimates were good for the axenic and non-axenic incubations, since aerobic bacterial degradation processes act upon free phytyldiol and phytol without high selectivity.

Comparison of the photodegradation rates of chlorophyll chlorin ring and phytol side chain in phytodetritus: is the phytyldiol versus phytol ratio (CPPI) a new biogeochemical index?

Abstract Rates of photodegradation of chlorophylls in their entirety and of chlorophyll phytyl chains, and time evolution of the Chlorophyll Phytyl side-Chain Photodegradation Index (CPPI) under visible light exposure were determined and compared in laboratory experiments. Killed phytoplanktonic cells of two widespread Bacillariophyceae (Thalassiosira rotula Meun. and Skeletonema costatum (Grev.) Cleve), one widespread Prymnesiophyceae (Emiliania huxleyi (Lohm.) May and Mohler) and one Chlorophyceae (Dunaliella tertiolecta Butch) were used as source of pigments (chlorophyll a, chlorophyll b and phaeophytin a). Chlorophyll and chlorophyll phytyl chain photodegradation and CPPI evolution showed apparent first-order kinetics with respect to light exposure. The in vitro determined degradation rates were approximately 3.5 times higher for the chlorophyll tetrapyrrolic structure than for the phytyl chain. Few variations of the relative photodegradation constant rates were observed between strains: less than 34% for chlorophyll a and 25% for chlorophyll phytyl chain at 20°C. Nonetheless, the photo-oxidation process of the phytyl chain (Q10=2.0) seems more affected by temperature than does chlorophyll a (Q10=1.4). Phytol loss in the dark controls have been attributed to bacterial degradation, and, in the case of S. costatum, chlorophyllase dephytylation seems to have enhanced the potential for bacterial biodegradation. From these results, it clearly appears that in small detrital particles not only chlorophyll a, chlorophyll b and phaeophytin but also their phytyl chains may be rapidly photodegraded in the upper portion of the euphotic zone. The use of the CPPI for monitoring the chlorophyll photo-oxidation process in the aquatic environment is discussed.

Biosynthesis of phytyl side-chain of chlorophyll a: apparent reutilization of carbon dioxide evolved during acetate assimilation in biosynthesis of chloroplastidic isoprenoid

Equal incorporation of either acetyl methyl or carboxy carbons into all carbon atoms of the phytyl side-chain of chlorophyll via doubly labelled acetyl CoA, with complete loss of methyl hydrogens, indicated that CO2 evolved from the carboxy carbon during acetate assimilation through the TCA cycle may be reutilized via the reductive pentose phosphate cycle followed by the glycolic pathway, while incorporation of [2-13C]glycerol and [6,6-2H2]glucose into the phytyl chain demonstrated the simultaneous operation of two distinct pathways, both the mevalonate pathway and the 1-deoxy-D-xylulose mediating pathways (non-mevalonate pathway) in isopentenyl diphosphate formation within liverwort chloroplasts.

Abiotic degradation of intact and photooxidized chlorophyll phytyl chain under simulated geological conditions

3,7,11,15-Tetramethyl-2-hexadecen-1-yl propionate (a model for the intact phytyl side chain of chlorophyll), 3-hydroxy-3,7,11,15-tetramethyl-1-hexadecen-1-yl propionate and 2-hydroxy-3-methylidene-7,11,15-trimethylhexadecyl propionate (models for a photo-oxidized chlorophyll phytyl chain) were heated in the presence of montmorillonite in order to simulate their abiotic degradation under geological conditions. Thermo-catalytic breakdown of phytyl propionate yielded most of the degradation products previously generated from phytol by heating in the presence of clays. Some interesting mechanisms involving protonation of the phytol double bond are proposed to explain the formation of phytanal and prist-1-ene observed during these manipulations. The abiotic degradation of 3-hydroxy-3,7,11,15-tetramethyl-1-hexadecen-1-yl propionate led to the production of 6,10,14-trimethylpentadecan-2-one, phytenals and phytenic acids as major products, whereas 2-hydroxy-3-methylidene-7,11,15-trimethylhexadecyl propionate afforded 6,10,14-trimethylpentadecan-2-one, 3,7,11,15-tetramethyl-2-oxohexadecanol-1 and 3,7,11,15-tetramethylhexadecan-1,2,3-triol. A kinetic study allowed comparison of the abiotic stability of intact and photooxidized chlorophyll phytyl chains in sediments and suggested potential markers for monitoring chlorophyll photodegradation.

Biosynthesis of chlorophyll a from 13C-labelled mevalonates and glycine in liverwort. Nonequivalent labelling of phytyl side chain

The phytyl side chain of chlorophyll a derived from exogenous 13C- and 2H-labelled mevalonate in cultured cells of two species of liverworts, Heteroscyphus ptanus and Lophocolea heterophylla, is shown to be preferentially labelled in the farnesyl diphosphate-derived portion, while its biosynthesis from exogenous 13C-glycine results in equivalent labelling.

Sesqui- and di-terpene biosynthesis from 13C labelled acetate and mevalonate in cultured cells of Heteroscyphus planus

Cultured cells of the liverwort, Heteroscyphus planus, accumulate a wide variety of sesquiterpenes and diterpenes of the clerodane type. 13C Atoms of [2-13C]acetate and [2-13C]- and [4,5-13C2]-mevalonates (MVAs) are incorporated into sesquiterpenes more extensively than into diterpenes by cultured cells of H. planus. (1S)-7-Methoxy-1,2-dihydrocadalene, a predominant sesquiterpene, and heteroscyphic acid A, a main diterpene, incorporating 13C labelled precursors were analysed by 13C NMR spectroscopy. Preferential labelling of the farnesyl diphosphate (FPP)-derived portion of heteroscyphic acid A was confirmed by 13C enriched peaks and 13C–13C couplings, while sesquiterpenes were labelled equivalently. From these results, it appears that separate sites for sesquiterpene and diterpene biosynthesis exist in cultured cells of H. planus as could be observed in higher plants. Since the same type of nonequivalent labelling was observed in the phytyl side chain of chlorophyll by other experiments, it is suggested that all compounds, which are formed from GGPP within chloroplasts, are biosynthesized partly via the condensation of FPP derived from exogenous MVA with endogenous isopentenyl diphosphate in chloroplasts. A 1,2-methyl migration of the methyl group originating at C-3 of MVA is also confirmed in the biosynthesis of the trans-clerodane skeleton.

Occurrence and significance of prist-1-ene in kerogen pyrolysates

A SERIES of acylic isoprenoid alkanes, of which pristane and phytane are typical, frequently occurs in crude oils, shales, coals, bitumens and so on. It is generally agreed that the primary source of these compounds is the phytyl side chain of chlorophyll(1,2) although the mechanisms of its incorporation into sediments and its subsequent diagenesis, are not completely understood. At present, little is known about the role of kerogen as a source, or sink, of isoprenoid moieties and we report here that the principal isoprenoid, obtained by the high temperature (600 degrees C) pyrolysis of kerogens has been identified as prist-1-ene.