chlorophyll-a and isopentenyl-pyrophosphate

Role of terpenes and isoprenoids has been pivotal in the survival and evolution of higher plants in various ecoregions. These products find application in the pharmaceutical, flavor fragrance, and biofuel industries. Fitness of plants in a wide range of environmental conditions entailed (i) evolution of secondary metabolic pathways enabling utilization of photosynthate for the synthesis of a variety of biomolecules, thereby facilitating diverse eco-interactive functions, and (ii) evolution of structural features for the sequestration of such compounds away from the mainstream primary metabolism to prevent autotoxicity. This review summarizes features and applications of terpene and isoprenoid compounds, comprising the largest class of secondary metabolites. Many of these terpene and isoprenoid biomolecules happen to be high-value bioproducts. They are essential components of all living organisms that are chemically highly variant. They are constituents of primary (quinones, chlorophylls, carotenoids, steroids) as well as secondary metabolism compounds with roles in signal transduction, reproduction, communication, climatic acclimation, defense mechanisms and more. They comprise single to several hundreds of repetitive five-carbon units of isopentenyl diphosphate (IPP) and its isomer dimethylallyl diphosphate (DMAPP). In plants, there are two pathways that lead to the synthesis of terpene and isoprenoid precursors, the cytosolic mevalonic acid (MVA) pathway and the plastidic methylerythritol phosphate (MEP) pathway. The diversity of terpenoids can be attributed to differential enzyme and substrate specificities and to secondary modifications acquired by terpene synthases. The biological role of secondary metabolites has been recognized as pivotal in the survival and evolution of higher plants. Terpenes and isoprenoids find application in pharmaceutical, nutraceutical, synthetic chemistry, flavor fragrance, and possibly biofuel industries.

Topics: Carotenoids; Chlorophyll; Hemiterpenes; Organophosphorus Compounds; Quinones; Terpenes

In cyanobacteria many compounds, including chlorophylls, carotenoids, and hopanoids, are synthesized from the isoprenoid precursors isopentenyl diphosphate (IPP) and dimethylallyl diphosphate. Isoprenoid biosynthesis in extracts of the cyanobacterium Synechocystis strain PCC 6803 grown under photosynthetic conditions, stimulated by pentose phosphate cycle substrates, does not appear to require methylerythritol phosphate pathway intermediates. The sll1556 gene, distantly related to type 2 IPP isomerase genes, was disrupted by insertion of a Kanr cassette. The mutant was fully viable under photosynthetic conditions although impaired in the utilization of pentose phosphate cycle substrates. Compared to the parental strain the Deltasll1556 mutant (i) is deficient in isoprenoid biosynthesis in vitro with substrates including glyceraldehyde-3-phosphate, fructose-6-phosphate, and glucose-6-phosphate; (ii) has smaller cells (diameter ca. 13% less); (iii) has fewer thylakoids (ca. 30% less); and (iv) has a more extensive fibrous outer wall layer. Isoprenoid biosynthesis is restored with pentose phosphate cycle substrates plus the recombinant Sll1556 protein in the Deltasll1556 supernatant fraction. IPP isomerase activity could not be demonstrated for the purified Sll1556 protein under our in vitro conditions. The reduction of thylakoid area and the effect on outer wall layer components are consistent with an impairment of isoprenoid biosynthesis in the mutant, possibly via hopanoid biosynthesis. Our findings are consistent with an alternate metabolic shunt for biosynthesis of isoprenoids.

Topics: Bacterial Proteins; Carotenoids; Cell Wall; Chlorophyll; Cyanobacteria; Fructosephosphates; Gene Silencing; Genes, Bacterial; Glucose-6-Phosphate; Glyceraldehyde 3-Phosphate; Hemiterpenes; Mutagenesis, Insertional; Organophosphorus Compounds; Pentose Phosphate Pathway; Terpenes; Thylakoids

In plants, the formation of isopentenyl diphosphate and dimethylallyl diphosphate, the central intermediates in the biosynthesis of isoprenoids, is compartmentalized: the mevalonate (MVA) pathway, which is localized to the cytosol, is responsible for the synthesis of sterols, certain sesquiterpenes, and the side chain of ubiquinone; in contrast, the recently discovered MVA-independent pathway, which operates in plastids, is involved in providing the precursors for monoterpenes, certain sesquiterpenes, diterpenes, carotenoids, and the side chains of chlorophylls and plastoquinone. Specific inhibitors of the MVA pathway (lovastatin) and the MVA-independent pathway (fosmidomycin) were used to perturb biosynthetic flux in Arabidopsis thaliana seedlings. The interaction between both pathways was studied at the transcriptional level by using GeneChip (Affymetrix) microarrays and at the metabolite level by assaying chlorophylls, carotenoids, and sterols. Treatment of seedlings with lovastatin resulted in a transient decrease in sterol levels and a transient increase in carotenoid as well as chlorophyll levels. After the initial drop, sterol amounts in lovastatin-treated seedlings recovered to levels above controls. As a response to fosmidomycin treatment, a transient increase in sterol levels was observed, whereas chlorophyll and carotenoid amounts decreased dramatically when compared with controls. At 96 h after fosmidomycin addition, the levels of all metabolites assayed (sterols, chlorophylls, and carotenoids) were substantially lower than in controls. Interestingly, these inhibitor-mediated changes were not reflected in altered gene expression levels of the genes involved in sterol, chlorophyll, and carotenoid metabolism. The lack of correlation between gene expression patterns and the accumulation of isoprenoid metabolites indicates that posttranscriptional processes may play an important role in regulating flux through isoprenoid metabolic pathways.

Topics: Arabidopsis; Base Sequence; Carotenoids; Chlorophyll; Cytosol; DNA Primers; Fosfomycin; Gene Expression Regulation, Plant; Hemiterpenes; Lovastatin; Organophosphorus Compounds; Plastids; Sterols

Isopentenyl diphosphate (IPP) is produced via two independent biosynthetic pathways in higher plants: the mevalonate (MVA) pathway in the cytoplasm and the non-mevalonate 2-C-methyl- D-erythritol-4-phosphate (MEP) pathway in plastids. It has been previously suggested that IPP or IPP-derived products can be exchanged between the cytoplasm and plastids. However, the issue of whether the exchanged products reflect efficient synthesis of functional isoprenoids remains unresolved. We fed exogenous mevalonic acid to the Arabidopsis thaliana (L.) Heynh. albino mutant cla1-1, a null mutant of the first-step enzyme in the MEP pathway. This resulted in the recovery of thylakoid membrane stacking in chloroplasts in the light, and the formation of prolamellar bodies and plastoglobuli in etioplasts in the dark. By contrast, exogenous lovastatin, an inhibitor of mevalonic acid biosynthesis, induced complete depigmentation and further inhibition of plastid development in both the light and the dark. These results suggest that mevalonic acid-derived products contribute to the formation of functional plastidic isoprenoids, such as the chlorophylls and carotenoids required for plastid development.

Topics: Arabidopsis; Chlorophyll; Chloroplasts; Darkness; Erythritol; Hemiterpenes; Light; Lovastatin; Mevalonic Acid; Microscopy, Electron; Mutation; Organophosphorus Compounds; Plastids; Sugar Phosphates

Transgenic plants of Arabidopsis thaliana (L.) Heynh. (ecotype Columbia) expressing the antisense AtMECT gene, encoding 2- C-methyl- D-erythritol 4-phosphate cytidylyltransferase, were generated to elucidate the physiological role of the nonmevalonate pathway for production of ent-kaurene, the latter being the plastidic precursor of gibberellins. In transformed plants pigmentation and accumulation of ent-kaurene were reduced compared to wild-type plants. Fosmidomycin, an inhibitor of 1-deoxy- D-xylulose 5-phosphate reductoisomerase (DXR), caused a similar depletion of these compounds in transgenic plants. These observations suggest that both AtMECT and DXR are important in the synthesis of isopentenyl diphosphate and dimethylallyl diphosphate and that ent-kaurene is mainly produced through the nonmevalonate pathway in the plastid.

Topics: Aldose-Ketose Isomerases; Arabidopsis; Carotenoids; Chlorophyll; Chlorophyll A; Chloroplasts; Cloning, Molecular; Diterpenes; Diterpenes, Kaurane; DNA, Antisense; Fosfomycin; Hemiterpenes; Mevalonic Acid; Molecular Sequence Data; Multienzyme Complexes; Nucleotidyltransferases; Organophosphorus Compounds; Oxidoreductases; Phenotype; Pigments, Biological; Plants, Genetically Modified

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.

Topics: Antioxidants; Chlorophyll; Chlorophyll A; Chromatography, Agarose; Chromatography, High Pressure Liquid; Chromatography, Liquid; Cinnamates; Depsides; Hemiterpenes; Isotope Labeling; Magnetic Resonance Spectroscopy; Mevalonic Acid; Optical Rotation; Organophosphorus Compounds; Plants; Polyisoprenyl Phosphates; Rosmarinic Acid; Sesquiterpenes

The enzyme isopentenyl pyrophosphate (IPP) isomerase catalyzes the reversible isomerization of IPP to produce dimethylallyl pyrophosphate, the initial substrate leading to the biosynthesis of carotenoids and many other long-chain isoprenoids. Expression of IPP isomerase, and of two enzymes specific to the carotenoid pathway (lycopene beta-cyclase and beta-carotene-C-4-oxygenase), was followed in the green unicellular alga Haematococcus pluvialis after exposure to high illumination. This alga uniquely accumulates carotenoids in the cytoplasm and in late developmental stages turns deep-red in color because of accumulation of ketocarotenoids in the cytosol. The carotenoid/chlorophyll ratio increased 3-fold in wild type and 6-fold in a precocious carotenoid-accumulating mutant (Car-3) within 24 h after increasing the illumination from 20 to 150 micromol photon m-2.s-1. Two cDNAs encoding IPP isomerase in Haematococcus, ipiHp1 and ipiHp2, were identified. Although otherwise highly similar (95% identity overall), the predicted sequence of ipiHp1 contained a 12-aa region not found in that of ipiHp2. This was reflected by a size difference between two polypeptides of 34 and 32.5 kDa, both of which reacted with an antibody to the product of ipiHp1. We suggest that the 32.5-kDa form is involved with the carotenoid accumulation in the cytoplasm, since the 32.5-kDa polypeptide was preferentially up-regulated by high light preceding the carotenoid increase and only this form was detected in red cysts.

Topics: Amino Acid Sequence; Animals; Carbon-Carbon Double Bond Isomerases; Carotenoids; Chlorophyll; Chlorophyta; Cloning, Molecular; Gene Expression Regulation, Developmental; Hemiterpenes; Intramolecular Lyases; Isoenzymes; Light; Molecular Sequence Data; Mutagenesis; Mutation; Organophosphorus Compounds; Pigments, Biological; RNA, Messenger; Sequence Alignment; Sequence Analysis