NTRC and TRX-f Coordinately Affect the Levels of Enzymes of Chlorophyll Biosynthesis in a Light-Dependent Manner
Redox regulation of plastid gene expression and different metabolic pathways promotes many activities of redox-sensitive proteins. We address the question of how the plastid redox state and the contributing reducing enzymes control the enzymes of tetrapyrrole biosynthesis (TBS). In higher plants, th...
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MDPI AG
2023-06-01
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| Series: | Cells |
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| Online Access: | https://www.mdpi.com/2073-4409/12/12/1670 |
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| author | Daniel Wittmann Peter Geigenberger Bernhard Grimm |
| author_facet | Daniel Wittmann Peter Geigenberger Bernhard Grimm |
| author_sort | Daniel Wittmann |
| collection | DOAJ |
| description | Redox regulation of plastid gene expression and different metabolic pathways promotes many activities of redox-sensitive proteins. We address the question of how the plastid redox state and the contributing reducing enzymes control the enzymes of tetrapyrrole biosynthesis (TBS). In higher plants, this metabolic pathway serves to produce chlorophyll and heme, among other essential end products. Because of the strictly light-dependent synthesis of chlorophyll, tight control of TBS requires a diurnal balanced supply of the precursor 5-aminolevulinic acid (ALA) to prevent the accumulation of photoreactive metabolic intermediates in darkness. We report on some TBS enzymes that accumulate in a light intensity-dependent manner, and their contents decrease under oxidizing conditions of darkness, low light conditions, or in the absence of NADPH-dependent thioredoxin reductase (NTRC) and thioredoxin f1 (TRX-f1). Analysis of single and double <i>trxf1</i> and <i>ntrc</i> mutants revealed a decreased content of the early TBS enzymes glutamyl-tRNA reductase (GluTR) and 5-aminolevulinic acid dehydratase (ALAD) instead of an exclusive decrease in enzyme activity. This effect was dependent on light conditions and strongly attenuated after transfer to high light intensities. Thus, it is suggested that a deficiency of plastid-localized thiol-redox transmitters leads to enhanced degradation of TBS enzymes rather than being directly caused by lower catalytic activity. The effects of the proteolytic activity of the Clp protease on TBS enzymes were studied by using Clp subunit-deficient mutants. The simultaneous lack of TRX and Clp activities in double mutants confirms the Clp-induced degradation of some TBS proteins in the absence of reductive activity of TRXs. In addition, we verified previous observations that decreased chlorophyll and heme levels in <i>ntrc</i> could be reverted to WT levels in the <i>ntrc/Δ2cp</i> triple mutant. The decreased synthesis of 5-aminolevulinic acid and porphobilinogen in <i>ntrc</i> was completely restored in <i>ntrc/Δ2cp</i> and correlated with WT-like levels of GluTR, ALAD, and other TBS proteins. |
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| institution | Directory Open Access Journal |
| issn | 2073-4409 |
| language | English |
| last_indexed | 2024-03-11T02:38:51Z |
| publishDate | 2023-06-01 |
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| spelling | doaj.art-7444d52b71644b3baa6f7a15cac022982023-11-18T09:44:13ZengMDPI AGCells2073-44092023-06-011212167010.3390/cells12121670NTRC and TRX-f Coordinately Affect the Levels of Enzymes of Chlorophyll Biosynthesis in a Light-Dependent MannerDaniel Wittmann0Peter Geigenberger1Bernhard Grimm2Institute of Biology/Plant Physiology, Humboldt-Universität zu Berlin, 10115 Berlin, GermanyDepartment Biology I, Ludwig-Maximilians-University Munich, 82152 Planegg-Martinsried, GermanyInstitute of Biology/Plant Physiology, Humboldt-Universität zu Berlin, 10115 Berlin, GermanyRedox regulation of plastid gene expression and different metabolic pathways promotes many activities of redox-sensitive proteins. We address the question of how the plastid redox state and the contributing reducing enzymes control the enzymes of tetrapyrrole biosynthesis (TBS). In higher plants, this metabolic pathway serves to produce chlorophyll and heme, among other essential end products. Because of the strictly light-dependent synthesis of chlorophyll, tight control of TBS requires a diurnal balanced supply of the precursor 5-aminolevulinic acid (ALA) to prevent the accumulation of photoreactive metabolic intermediates in darkness. We report on some TBS enzymes that accumulate in a light intensity-dependent manner, and their contents decrease under oxidizing conditions of darkness, low light conditions, or in the absence of NADPH-dependent thioredoxin reductase (NTRC) and thioredoxin f1 (TRX-f1). Analysis of single and double <i>trxf1</i> and <i>ntrc</i> mutants revealed a decreased content of the early TBS enzymes glutamyl-tRNA reductase (GluTR) and 5-aminolevulinic acid dehydratase (ALAD) instead of an exclusive decrease in enzyme activity. This effect was dependent on light conditions and strongly attenuated after transfer to high light intensities. Thus, it is suggested that a deficiency of plastid-localized thiol-redox transmitters leads to enhanced degradation of TBS enzymes rather than being directly caused by lower catalytic activity. The effects of the proteolytic activity of the Clp protease on TBS enzymes were studied by using Clp subunit-deficient mutants. The simultaneous lack of TRX and Clp activities in double mutants confirms the Clp-induced degradation of some TBS proteins in the absence of reductive activity of TRXs. In addition, we verified previous observations that decreased chlorophyll and heme levels in <i>ntrc</i> could be reverted to WT levels in the <i>ntrc/Δ2cp</i> triple mutant. The decreased synthesis of 5-aminolevulinic acid and porphobilinogen in <i>ntrc</i> was completely restored in <i>ntrc/Δ2cp</i> and correlated with WT-like levels of GluTR, ALAD, and other TBS proteins.https://www.mdpi.com/2073-4409/12/12/1670thioredoxinNADPH-dependent thioredoxin reductasechlorophyll synthesis5-aminolevulinic acid synthesischloroplast biogenesisphotosynthesis |
| spellingShingle | Daniel Wittmann Peter Geigenberger Bernhard Grimm NTRC and TRX-f Coordinately Affect the Levels of Enzymes of Chlorophyll Biosynthesis in a Light-Dependent Manner Cells thioredoxin NADPH-dependent thioredoxin reductase chlorophyll synthesis 5-aminolevulinic acid synthesis chloroplast biogenesis photosynthesis |
| title | NTRC and TRX-f Coordinately Affect the Levels of Enzymes of Chlorophyll Biosynthesis in a Light-Dependent Manner |
| title_full | NTRC and TRX-f Coordinately Affect the Levels of Enzymes of Chlorophyll Biosynthesis in a Light-Dependent Manner |
| title_fullStr | NTRC and TRX-f Coordinately Affect the Levels of Enzymes of Chlorophyll Biosynthesis in a Light-Dependent Manner |
| title_full_unstemmed | NTRC and TRX-f Coordinately Affect the Levels of Enzymes of Chlorophyll Biosynthesis in a Light-Dependent Manner |
| title_short | NTRC and TRX-f Coordinately Affect the Levels of Enzymes of Chlorophyll Biosynthesis in a Light-Dependent Manner |
| title_sort | ntrc and trx f coordinately affect the levels of enzymes of chlorophyll biosynthesis in a light dependent manner |
| topic | thioredoxin NADPH-dependent thioredoxin reductase chlorophyll synthesis 5-aminolevulinic acid synthesis chloroplast biogenesis photosynthesis |
| url | https://www.mdpi.com/2073-4409/12/12/1670 |
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