Abstract
Photosynthetic organisms must achieve a delicate balance between the light energy absorbed by chlorophyll and their capacity to channel that energy into productive photochemical reactions. Release of excess absorbed energy in the cell can cause lethal photooxidative damage. We identified a basic helix-loop-helix (bHLH) transcription factor, designated PHYTOCHROME-INTERACTING FACTOR 1 (PIF1), that negatively regulates chlorophyll biosynthesis. pif1 mutant seedlings accumulate excess free protochlorophyllide when grown in the dark, with consequent lethal bleaching upon exposure to light. PIF1 interacts specifically with the photoactivated conformer of phytochromes A and B, suggesting a signaling pathway by which chlorophyll biosynthetic rates are tightly controlled during the critical initial emergence of seedlings from subterranean darkness into sunlight.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, Non-P.H.S.
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Arabidopsis
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Arabidopsis Proteins / physiology*
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Basic Helix-Loop-Helix Leucine Zipper Transcription Factors / physiology*
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Basic Helix-Loop-Helix Transcription Factors
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Biological Evolution
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Chlorophyll / biosynthesis*
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DNA, Plant / metabolism
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DNA-Binding Proteins / physiology
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Gene Expression Regulation, Plant
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Helix-Loop-Helix Motifs*
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Photochemistry
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Phytochrome / physiology
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Protein Binding
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Seedlings
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Signal Transduction
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Transcription Factors / physiology
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Transcription, Genetic
Substances
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Arabidopsis Proteins
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Basic Helix-Loop-Helix Leucine Zipper Transcription Factors
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Basic Helix-Loop-Helix Transcription Factors
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DNA, Plant
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DNA-Binding Proteins
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PIF1 protein, Arabidopsis
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PIF3 protein, Arabidopsis
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Transcription Factors
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Phytochrome
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Chlorophyll