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PHYTOCHROME-INTERACTING FACTOR 1 Is a Critical bHLH Regulator of Chlorophyll Biosynthesis

2004; American Association for the Advancement of Science; Volume: 305; Issue: 5692 Linguagem: Inglês

10.1126/science.1099728

1095-9203

Enamul Huq, Bassem Al‐Sady, Matthew E. Hudson, Chanhong Kim, Klaus Apel, Peter H. Quail,

Plant Molecular Biology Research

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.