poc1: An Arabidopsis mutant perturbed in phytochrome signaling because of a T DNA insertion in the promoter of PIF3, a gene encoding a phytochrome-interacting bHLH protein

Karen J. Halliday, Matthew Hudson, Min Ni, Minmin Qin, Peter H. Quail

Research output: Contribution to journalArticlepeer-review

Abstract

The phytochrome family of informational photoreceptors has a central role in regulating light-responsive gene expression, but the mechanism of intracellular signal transduction has remained elusive. In a genetic screen for T DNA-tagged Arabidopsis mutants affected in early signaling intermediates, we identified poc1 (photocurrent 1), which exhibits enhanced responsiveness to red light. This phenotype is absent in a phyB (phytochrome B) null mutant background, indicating that the poc1 mutation enhances phyB signal transduction. The T DNA insertion in poc1 was found to be located in the promoter region of PIF3, a gene encoding a basic helix-loop-helix protein. The mutant phenotype seems to result from insertion-induced overexpression of this gene in red-light-grown seedlings, consistent with PIF3 functioning as a positively acting signaling intermediate. These findings, combined with data from a separate yeast two-hybrid screen that identified PIF3 as a phytochrome-interacting factor necessary for normal signaling, provide evidence that phytochrome signal transduction may include a direct pathway to photoresponsive nuclear genes via physical interaction of the photoreceptor molecules with the potential transcriptional regulator PIF3.

Original languageEnglish (US)
Pages (from-to)5832-5837
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume96
Issue number10
DOIs
StatePublished - May 11 1999
Externally publishedYes

Keywords

  • Photoreceptor
  • Signal transduction

ASJC Scopus subject areas

  • General

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