Translational regulation of light-harvesting complex expression during photoacclimation to high-light in Chlamydomonas reinhardtii

S M McKim, D G Durnford

Research output: Contribution to journalArticle

35 Citations (Scopus)

Abstract

When challenged with excess light, the green alga Chlamydomonas reinhardtii responds, in part, by down-regulating light harvesting capacity at Photosystem II while concomitantly reorganising cellular metabolism to increase sink capacity. We examined the role of translational control during different stages of photoacclimation by analysing polysome profiles of two different light-harvesting complex (LHC) genes encoding a major LHCII component (Lhcbm) and CP29 (Lhcb4) plus iron superoxide dismutase (FeSOD), and through measurement of protein synthesis by in vivo labelling. Within two hours following transfer of low-light (LL) acclimated cultures into high-light (HL), Lhcbm transcripts are off-loaded from polysomes indicating a decline in translational initiation. Lhcbm translational repression at two hours was specific since FeSOD mRNA remained associated with polysomes and in vivo labelling showed an increase in overall protein synthesis. After 4 hours HL exposure, however, a global disassembly of polysomes was detected suggesting a general decline in translational initiation. Interestingly, the decrease in polysomes coincides with maximal FeSOD transcript levels emphasizing that transcript profiles do not always accurately reflect gene expression. Within 8 hours after LL to HL shift, polysomes reform and all transcripts examined are loaded back onto polysomes. Disassembly of polysomes was mimicked by hydrogen peroxide application to non-shifted cultures suggesting that production of hydrogen peroxide due to HL-stress may effect the general decline in polysomes observed during HL acclimation.

Original languageEnglish
Pages (from-to)857-65
Number of pages9
JournalPlant Physiology and Biochemistry
Volume44
Issue number11-12
DOIs
Publication statusPublished - 14 Nov 2006

Fingerprint

Chlamydomonas reinhardtii
polyribosomes
Polyribosomes
light harvesting complex
Light
Hydrogen Peroxide
hydrogen peroxide
protein synthesis
Methyl Green
Chlorophyta
Photosystem II Protein Complex
Acclimatization
major genes
photosystem II
Superoxide Dismutase
acclimation
superoxide dismutase
Proteins
iron
Gene Expression

Keywords

  • Acclimatization
  • Algal Proteins
  • Animals
  • Chlamydomonas reinhardtii
  • Gene Expression Regulation, Plant
  • Light
  • Photosystem II Protein Complex
  • Protein Biosynthesis
  • Journal Article
  • Research Support, Non-U.S. Gov't

Cite this

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abstract = "When challenged with excess light, the green alga Chlamydomonas reinhardtii responds, in part, by down-regulating light harvesting capacity at Photosystem II while concomitantly reorganising cellular metabolism to increase sink capacity. We examined the role of translational control during different stages of photoacclimation by analysing polysome profiles of two different light-harvesting complex (LHC) genes encoding a major LHCII component (Lhcbm) and CP29 (Lhcb4) plus iron superoxide dismutase (FeSOD), and through measurement of protein synthesis by in vivo labelling. Within two hours following transfer of low-light (LL) acclimated cultures into high-light (HL), Lhcbm transcripts are off-loaded from polysomes indicating a decline in translational initiation. Lhcbm translational repression at two hours was specific since FeSOD mRNA remained associated with polysomes and in vivo labelling showed an increase in overall protein synthesis. After 4 hours HL exposure, however, a global disassembly of polysomes was detected suggesting a general decline in translational initiation. Interestingly, the decrease in polysomes coincides with maximal FeSOD transcript levels emphasizing that transcript profiles do not always accurately reflect gene expression. Within 8 hours after LL to HL shift, polysomes reform and all transcripts examined are loaded back onto polysomes. Disassembly of polysomes was mimicked by hydrogen peroxide application to non-shifted cultures suggesting that production of hydrogen peroxide due to HL-stress may effect the general decline in polysomes observed during HL acclimation.",
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Translational regulation of light-harvesting complex expression during photoacclimation to high-light in Chlamydomonas reinhardtii. / McKim, S M; Durnford, D G.

In: Plant Physiology and Biochemistry, Vol. 44, No. 11-12, 14.11.2006, p. 857-65.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Translational regulation of light-harvesting complex expression during photoacclimation to high-light in Chlamydomonas reinhardtii

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AU - Durnford, D G

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N2 - When challenged with excess light, the green alga Chlamydomonas reinhardtii responds, in part, by down-regulating light harvesting capacity at Photosystem II while concomitantly reorganising cellular metabolism to increase sink capacity. We examined the role of translational control during different stages of photoacclimation by analysing polysome profiles of two different light-harvesting complex (LHC) genes encoding a major LHCII component (Lhcbm) and CP29 (Lhcb4) plus iron superoxide dismutase (FeSOD), and through measurement of protein synthesis by in vivo labelling. Within two hours following transfer of low-light (LL) acclimated cultures into high-light (HL), Lhcbm transcripts are off-loaded from polysomes indicating a decline in translational initiation. Lhcbm translational repression at two hours was specific since FeSOD mRNA remained associated with polysomes and in vivo labelling showed an increase in overall protein synthesis. After 4 hours HL exposure, however, a global disassembly of polysomes was detected suggesting a general decline in translational initiation. Interestingly, the decrease in polysomes coincides with maximal FeSOD transcript levels emphasizing that transcript profiles do not always accurately reflect gene expression. Within 8 hours after LL to HL shift, polysomes reform and all transcripts examined are loaded back onto polysomes. Disassembly of polysomes was mimicked by hydrogen peroxide application to non-shifted cultures suggesting that production of hydrogen peroxide due to HL-stress may effect the general decline in polysomes observed during HL acclimation.

AB - When challenged with excess light, the green alga Chlamydomonas reinhardtii responds, in part, by down-regulating light harvesting capacity at Photosystem II while concomitantly reorganising cellular metabolism to increase sink capacity. We examined the role of translational control during different stages of photoacclimation by analysing polysome profiles of two different light-harvesting complex (LHC) genes encoding a major LHCII component (Lhcbm) and CP29 (Lhcb4) plus iron superoxide dismutase (FeSOD), and through measurement of protein synthesis by in vivo labelling. Within two hours following transfer of low-light (LL) acclimated cultures into high-light (HL), Lhcbm transcripts are off-loaded from polysomes indicating a decline in translational initiation. Lhcbm translational repression at two hours was specific since FeSOD mRNA remained associated with polysomes and in vivo labelling showed an increase in overall protein synthesis. After 4 hours HL exposure, however, a global disassembly of polysomes was detected suggesting a general decline in translational initiation. Interestingly, the decrease in polysomes coincides with maximal FeSOD transcript levels emphasizing that transcript profiles do not always accurately reflect gene expression. Within 8 hours after LL to HL shift, polysomes reform and all transcripts examined are loaded back onto polysomes. Disassembly of polysomes was mimicked by hydrogen peroxide application to non-shifted cultures suggesting that production of hydrogen peroxide due to HL-stress may effect the general decline in polysomes observed during HL acclimation.

KW - Acclimatization

KW - Algal Proteins

KW - Animals

KW - Chlamydomonas reinhardtii

KW - Gene Expression Regulation, Plant

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KW - Photosystem II Protein Complex

KW - Protein Biosynthesis

KW - Journal Article

KW - Research Support, Non-U.S. Gov't

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SN - 0981-9428

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