Molecular bases for the constitutive photomorphogenic phenotypes in .

The transition from skotomorphogenesis to photomorphogenesis is regulated in part by the COP1/SPA complex and phytochrome-interacting factors (PIFs) in The constitutive photomorphogenic (cop) phenotypes of and mutants have been shown to result from a high abundance of positively acting transcription factors. Here, we show that the four major PIF proteins are unstable in mutants and that overexpression of , , and suppresses phenotypes in the dark. A comparison of the transcriptome data among , and reveals remarkably overlapping gene expression profiles with preferential regulation of PIF direct target genes. Additionally, HFR1 strongly inhibits the binding and transcriptional activation activity of PIF1 in the dark. Taken together, these data suggest that the cop phenotypes of the and mutants are due to a combination of the reduced level of PIFs, increased levels of positively acting transcription factors (e.g. HY5/HFR1) and the HFR1-mediated inhibition of PIF-targeted gene expression in the dark. This article has an associated 'The people behind the papers' interview.