Details
| Original language | English |
|---|---|
| Pages (from-to) | 1351-9 |
| Number of pages | 9 |
| Journal | Philosophical Transactions of the Royal Society B: Biological Sciences |
| Volume | 355 |
| Issue number | 1402 |
| Publication status | Published - 29 Oct 2000 |
Abstract
Chloroplasts are cytoplasmic organelles whose primary function is photosynthesis, but which also contain small, specialized and quasi-autonomous genetic systems. In photosynthesis, two energy converting photosystems are connected, electrochemically, in series. The connecting electron carriers are oxidized by photosystem I (PS I) and reduced by photosystem II (PS II). It has recently been shown that the oxidation reduction state of one connecting electron carrier, plastoquinone, controls transcription of chloroplast genes for reaction centre proteins of the two photosystems. The control counteracts the imbalance in electron transport that causes it: oxidized plastoquinone induces PS II and represses PS I; reduced plastoquinone induces PS I and represses PS II. This complementarity is observed both in vivo, using light favouring one or other photosystem, and in vitro, when site-specific electron transport inhibitors are added to transcriptionally and photosynthetically active chloroplasts. There is thus a transcriptional level of control that has a regulatory function similar to that of purely post-translational 'state transitions' in which the redistribution of absorbed excitation energy between photosystems is mediated by thylakoid membrane protein phosphorylation. The changes in rates of transcription that are induced by spectral changes in vivo can be detected even before the corresponding state transitions are complete, suggesting the operation of a branched pathway of redox signal transduction. These findings suggest a mechanism for adjustment of photosystem stoichiometry in which initial events involve a sensor of the redox state of plastoquinone, and may thus be the same as the initial events of state transitions. Redox control of chloroplast transcription is also consistent with the proposal that a direct regulatory coupling between electron transport and gene expression determines the function and composition of the chloroplast's extra-nuclear genetic system.
Keywords
- Animals, Chloroplasts/metabolism, Electron Transport, Gene Expression Regulation, Plant, Genes, Plant, Genome, Plant, Oxidation-Reduction, Photosynthesis/physiology, Photosynthetic Reaction Center Complex Proteins/genetics, Photosystem I Protein Complex, Photosystem II Protein Complex, Plastoquinone/metabolism, Transcription, Genetic
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In: Philosophical Transactions of the Royal Society B: Biological Sciences, Vol. 355, No. 1402, 29.10.2000, p. 1351-9.
Research output: Contribution to journal › Review article › Research › peer review
}
TY - JOUR
T1 - Balancing the two photosystems
T2 - photosynthetic electron transfer governs transcription of reaction centre genes in chloroplasts
AU - Allen, J F
AU - Pfannschmidt, T
PY - 2000/10/29
Y1 - 2000/10/29
N2 - Chloroplasts are cytoplasmic organelles whose primary function is photosynthesis, but which also contain small, specialized and quasi-autonomous genetic systems. In photosynthesis, two energy converting photosystems are connected, electrochemically, in series. The connecting electron carriers are oxidized by photosystem I (PS I) and reduced by photosystem II (PS II). It has recently been shown that the oxidation reduction state of one connecting electron carrier, plastoquinone, controls transcription of chloroplast genes for reaction centre proteins of the two photosystems. The control counteracts the imbalance in electron transport that causes it: oxidized plastoquinone induces PS II and represses PS I; reduced plastoquinone induces PS I and represses PS II. This complementarity is observed both in vivo, using light favouring one or other photosystem, and in vitro, when site-specific electron transport inhibitors are added to transcriptionally and photosynthetically active chloroplasts. There is thus a transcriptional level of control that has a regulatory function similar to that of purely post-translational 'state transitions' in which the redistribution of absorbed excitation energy between photosystems is mediated by thylakoid membrane protein phosphorylation. The changes in rates of transcription that are induced by spectral changes in vivo can be detected even before the corresponding state transitions are complete, suggesting the operation of a branched pathway of redox signal transduction. These findings suggest a mechanism for adjustment of photosystem stoichiometry in which initial events involve a sensor of the redox state of plastoquinone, and may thus be the same as the initial events of state transitions. Redox control of chloroplast transcription is also consistent with the proposal that a direct regulatory coupling between electron transport and gene expression determines the function and composition of the chloroplast's extra-nuclear genetic system.
AB - Chloroplasts are cytoplasmic organelles whose primary function is photosynthesis, but which also contain small, specialized and quasi-autonomous genetic systems. In photosynthesis, two energy converting photosystems are connected, electrochemically, in series. The connecting electron carriers are oxidized by photosystem I (PS I) and reduced by photosystem II (PS II). It has recently been shown that the oxidation reduction state of one connecting electron carrier, plastoquinone, controls transcription of chloroplast genes for reaction centre proteins of the two photosystems. The control counteracts the imbalance in electron transport that causes it: oxidized plastoquinone induces PS II and represses PS I; reduced plastoquinone induces PS I and represses PS II. This complementarity is observed both in vivo, using light favouring one or other photosystem, and in vitro, when site-specific electron transport inhibitors are added to transcriptionally and photosynthetically active chloroplasts. There is thus a transcriptional level of control that has a regulatory function similar to that of purely post-translational 'state transitions' in which the redistribution of absorbed excitation energy between photosystems is mediated by thylakoid membrane protein phosphorylation. The changes in rates of transcription that are induced by spectral changes in vivo can be detected even before the corresponding state transitions are complete, suggesting the operation of a branched pathway of redox signal transduction. These findings suggest a mechanism for adjustment of photosystem stoichiometry in which initial events involve a sensor of the redox state of plastoquinone, and may thus be the same as the initial events of state transitions. Redox control of chloroplast transcription is also consistent with the proposal that a direct regulatory coupling between electron transport and gene expression determines the function and composition of the chloroplast's extra-nuclear genetic system.
KW - Animals
KW - Chloroplasts/metabolism
KW - Electron Transport
KW - Gene Expression Regulation, Plant
KW - Genes, Plant
KW - Genome, Plant
KW - Oxidation-Reduction
KW - Photosynthesis/physiology
KW - Photosynthetic Reaction Center Complex Proteins/genetics
KW - Photosystem I Protein Complex
KW - Photosystem II Protein Complex
KW - Plastoquinone/metabolism
KW - Transcription, Genetic
U2 - 10.1098/rstb.2000.0697
DO - 10.1098/rstb.2000.0697
M3 - Review article
C2 - 11127990
VL - 355
SP - 1351
EP - 1359
JO - Philosophical Transactions of the Royal Society B: Biological Sciences
JF - Philosophical Transactions of the Royal Society B: Biological Sciences
SN - 0962-8436
IS - 1402
ER -