Phytochrome A

UniProtKB accession:  P14712

Grouped By:  Matching UniProtKB accession

UniProtKB description:  Regulatory photoreceptor which exists in two forms that are reversibly interconvertible by light: the Pr form that absorbs maximally in the red region of the spectrum and the Pfr form that absorbs maximally in the far-red region. Photoconversion of Pr to Pfr induces an array of morphogenetic responses, whereas reconversion of Pfr to Pr cancels the induction of those responses. Pfr controls the expression of a number of nuclear genes including those encoding the small subunit of ribulose-bisphosphate carboxylase, chlorophyll A/B binding protein, protochlorophyllide reductase, rRNA, etc. It also controls the expression of its own gene(s) in a negative feedback fashion. Involved in the flowering time regulation. Can phosphorylate FHY1 and, possibly, FHL, in red light conditions; this inactivates their co-shuttling to the nucleus (PubMed:19208901). Regulates phototropic responses both in the nucleus (e.g. hypocotyl elongation and cotyledon opening under high-irradiance conditions and seed germination under very-low-fluence conditions) and in the cytoplasm (e.g. negative gravitropism in blue light and red-enhanced phototropism) (PubMed:17566111). Promotes seed germination, suppression of hypocotyl elongation, and randomization of hypocotyl growth orientation in far-red light; these responses to far-red light are repressed by UNE10/PIF8 (PubMed:31732705). Stabilizes UNE10/PIF8 but sequesters PIF3/PAP3 from its target genes promoters in far-red light (PubMed:31732705).