chlorophyll-a and levulinic-acid

Plants in response to different environmental cues need to modulate the expression of nuclear and chloroplast genomes that are in constant communication. To understand the signals that are responsible for inter-organellar communication, levulinic acid (LA), an inhibitor of 5-aminolevulinic acid dehydratase, was used to suppress the synthesis of pyrrole-derived tetrapyrroles chlorophylls. Although, it does not specifically inhibit carotenoid biosynthesis enzymes, LA reduced the carotenoid contents during photomorphogenesis of etiolated Arabidopsis seedlings. The expression of nuclear genes involved in carotenoid biosynthesis, i.e., geranylgeranyl diphosphate synthase, phytoene synthase, and phytoene desaturase, was downregulated in LA-treated seedlings. Similarly, the transcript abundance of nuclear genes, i.e., Lhcb1, PsbO, and RcbS, coding for chloroplastic proteins was severely attenuated in LA-treated samples. In contrast, LA treatment did not affect the transcript abundance of chalcone synthase, a marker gene for cytoplasm, and β-ATP synthase, a marker gene for mitochondria. This demonstrates the retrograde signaling from chloroplast to nucleus to suppress chloroplastic proteins during impaired chloroplast development. However, under identical conditions in LA-treated tetrapyrrole-deficient gun5 mutant, retrograde signal continued. The tetrapyrrole biosynthesis inhibitor LA suppressed formation of all tetrapyrroles both in WT and gun5. This rules out the role of tetrapyrroles as signaling molecules in WT and gun5. The removal of LA from the Arabidopsis seedlings restored the chlorophyll and carotenoid contents and expression of nuclear genes coding for chloroplastic proteins involved in chloroplast biogenesis. Therefore, LA could be used to modulate chloroplast biogenesis at a desired phase of chloroplast development.

Topics: Acyltransferases; Arabidopsis; Arabidopsis Proteins; Carotenoids; Chlorophyll; Chloroplasts; Gene Expression Regulation, Plant; Levulinic Acids; Light-Harvesting Protein Complexes; Lyases; Mutation; Oxidoreductases; Seedlings; Signal Transduction; Tetrapyrroles

Chloroplast development and chlorophyll biosynthesis are co-regulated. Treatment by levulinic acid resulted in a linear relation in both chlorophyll and carotenoid contents, during greening of etiolated French bean leaf discs. Chlorophyll biosynthesis appeared to control that of caroteins. In the presence of levulinic acid; at different levels, photosystem II (PS II) activity decreased when expressed on a chlorophyll basis. Chlorophyllase activity was increased progressively by increasing levulinic acid concentration. Thus, levulinic acid could be used to arrest the light-induced chloroplast development at a desired phase of greening and acts as determinator of chloroplast development in green tissues.

Topics: Aminolevulinic Acid; Carboxylic Ester Hydrolases; Carotenoids; Chlorophyll; Darkness; Electron Transport; Fabaceae; Levulinic Acids; Light; Photosynthesis; Pigments, Biological; Plant Leaves; Plants, Medicinal; Porphobilinogen Synthase

Steady-state mRNA levels of the three nuclear genes cab1, rbcS1 and rbcS2 (coding for the light-harvesting chlorophyll-binding protein (LHCP) and the small subunit of ribulose 1,5-bisphosphate carboxylase, respectively) and of the two plastid-encoded genes rbcL and psaA2 (coding for the large subunit of the carboxylase and a member of the P700 chlorophyll a protein, respectively) have been investigated in synchronized Chlamydomonas cells in response to light and inhibitors interfering with chlorophyll synthesis. The accumulation of cab1, rbcS1 and psaA2 transcripts is light-dependent, whereas transcripts from rbcS2 and rbcL genes are present in high amounts in the light and in the dark. Dioxoheptanoic acid, an inhibitor blocking chlorophyll synthesis prior to porphyrin formation, does not affect the accumulation of all five mRNAs. However, inhibition of chlorophyll synthesis by incubating cells with dipyridyl, cycloheximide or nitrogen promotes the accumulation of porphyrin compounds, but specifically prevents the accumulation of light-dependent transcripts. Although functionally unrelated, these inhibitors are known to block an Fe-dependent oxygenase, which is involved in the formation of the isocyclic ring in the chlorophyll molecule. The data are explained as a control by chlorophyll precursors over the accumulation of light-dependent transcripts.

Topics: 2,2'-Dipyridyl; Chlamydomonas; Chloramphenicol; Chlorophyll; Cycloheximide; DNA Probes; Hemin; Heptanoates; Iron; Levulinic Acids; Light; Light-Harvesting Protein Complexes; Nucleic Acid Hybridization; Photochemistry; Photosynthetic Reaction Center Complex Proteins; Plant Proteins; Protein Precursors; Pyridazines; RNA, Messenger; Transcription, Genetic

Protein synthesis, normally a light-dependent process in isolated mature chloroplasts of Euglena gracilis var. bacillaris will take place in darkness if ATP and Mg2+ (ATP/Mg) are supplied. Either 5 or 10 mM ATP plus 15 mM MgCl2 are optimal and rates equal to those in the light can be obtained. Since ATP and Mg2+ are not stoichiometrically related, and since the optimal Mg2+ concentration is similar to that which stabilizes chloroplast ribosomes in vitro, it is suggested that the chloroplast is freely permeable to Mg2+ under these conditions. Protein synthesis under these conditions is not inhibited appreciably by DCMU, FCCP, cycloheximide, or by the addition of ribonuclease, but is highly sensitive to chloramphenicol. Carbon dioxide fixation is also a light-dependent process in isolated mature chloroplasts from Euglena, but addition of ATP (5 mM) and fructose bisphosphate (5 mM) plus aldolase (1.0 unit/ml) (fructose-1,6-bisphosphate/aldolase) yields CO2 fixation rates in darkness that are 43% of those normally obtained in the light. Mg2+ higher than 1.0 mM (e.g., 16 mM) is somewhat inhibitory. Chlorophyll synthesis from 5-aminolevulinate in 36 h developing chloroplasts from Euglena is also light-dependent, but addition of ATP/Mg and fructose-1,6-bis-phosphate/aldolase in darkness brings about the accumulation of a compound having the same RF on chromatography as protochlorophyllide from Barley; a subsequent brief illumination of the chloroplasts converts this compound to a compound with the RF of chlorophyll. Thus Euglena chloroplasts supplied with appropriate additions can carry out protein synthesis, carbon dioxide fixation and most of chlorophyll synthesis in darkness. This versatility is appropriate in photosynthetic organelles isolated from photo-organotrophic cells.

Topics: Adenosine Triphosphate; Animals; Carbon Dioxide; Chlorophyll; Chloroplasts; Darkness; Euglena; Fructose-Bisphosphate Aldolase; Fructosephosphates; Kinetics; Levulinic Acids; Magnesium; Protein Biosynthesis

Laevulinic acid (Lev) was used to control the rate of protocholorophyllide (PChl) regeneration in the leaves of dark-grown seedlings of barley (Hordeum vulgare) after a brief light treatment. In the leaves given Lev, at concentrations that severely block the resynthesis of protochlorophyllide, there was a massive overproduction of delta-aminolaevulinic acid (AmLev) that was well in excess of that required for the regeneration of PChl observed in the control leaves. Lev, at low concentrations, slightly delayed regeneration and held up, rather than inhibited, the utilization of the AmLev, which accumulated in the tissues. The overproduction and uncontrolled formation of AmLev also occurred in dark-grown leaves treated with a high concentration of Lev and given a light treatment of just sufficient energy to photoreduce only small quantities of the endogenous PChl. Experiments in which a high level of free PChl was induced by incubating the leaves in AmLev indicated that the active species of PChl was that associated with, and bound to, the PChl reductase protein. The results strongly demonstrate a close relationship between the PChl-protein complex and the ability of the leaves to synthesize AmLev.

Topics: Aminolevulinic Acid; Chlorophyll; Darkness; Hordeum; Levulinic Acids; Light; Macromolecular Substances; Plants; Protochlorophyllide; Spectrophotometry

Topics: 5-Aminolevulinate Synthetase; Acridines; Anti-Bacterial Agents; Azaguanine; Bacteriochlorophylls; Carbon Isotopes; Catalase; Chloramphenicol; Chlorophyll; Dactinomycin; DNA; Levulinic Acids; Ligases; Metabolism; Mitomycin; Mitomycins; Pharmacology; Proteins; Radiometry; Research; Rhodobacter sphaeroides; Rhodopseudomonas; RNA; Spectrophotometry

Topics: Anti-Bacterial Agents; Carbon Isotopes; Chloramphenicol; Chlorophyll; Chromatography; Levulinic Acids; Oxygen; Pharmacology; Phenylalanine; Photosynthesis; Porphyrins; Proteins; Puromycin; Research; Rhodopseudomonas

Topics: Chlorophyll; Chloroplasts; Euglena; Hydro-Lyases; Levulinic Acids; Metabolism; Porphyrins; Research

Topics: Amino Acids; Carbon; Carbon Isotopes; Chlorella; Chlorophyll; Citric Acid Cycle; Eukaryota; Glutamates; Levulinic Acids; Malonates; Metabolism; Proline; Research; Succinates

Topics: Adenine; Adenine Nucleotides; Adenosine Triphosphate; Antimetabolites; Chlorophyll; Levulinic Acids; Metabolism; Nucleosides; Nucleotides; Orotic Acid; Pharmacology; Porphyrins; Research; Rhodopseudomonas; Thymine; Uracil