8isi

Structural highlights

Function

PHYA_ARATH 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).^{[1] [2] [3] [4] [5] [6] [7]}

References

1. ↑ Kim DH, Kang JG, Yang SS, Chung KS, Song PS, Park CM. A phytochrome-associated protein phosphatase 2A modulates light signals in flowering time control in Arabidopsis. Plant Cell. 2002 Dec;14(12):3043-56. PMID:12468726
2. ↑ Ryu JS, Kim JI, Kunkel T, Kim BC, Cho DS, Hong SH, Kim SH, Fernandez AP, Kim Y, Alonso JM, Ecker JR, Nagy F, Lim PO, Song PS, Schafer E, Nam HG. Phytochrome-specific type 5 phosphatase controls light signal flux by enhancing phytochrome stability and affinity for a signal transducer. Cell. 2005 Feb 11;120(3):395-406. PMID:15707897 doi:http://dx.doi.org/10.1016/j.cell.2004.12.019
3. ↑ Rösler J, Klein I, Zeidler M. Arabidopsis fhl/fhy1 double mutant reveals a distinct cytoplasmic action of phytochrome A. Proc Natl Acad Sci U S A. 2007 Jun 19;104(25):10737-42. PMID:17566111 doi:10.1073/pnas.0703855104
4. ↑ Shen Y, Zhou Z, Feng S, Li J, Tan-Wilson A, Qu LJ, Wang H, Deng XW. Phytochrome A mediates rapid red light-induced phosphorylation of Arabidopsis FAR-RED ELONGATED HYPOCOTYL1 in a low fluence response. Plant Cell. 2009 Feb;21(2):494-506. PMID:19208901 doi:10.1105/tpc.108.061259
5. ↑ Yang SW, Jang IC, Henriques R, Chua NH. FAR-RED ELONGATED HYPOCOTYL1 and FHY1-LIKE associate with the Arabidopsis transcription factors LAF1 and HFR1 to transmit phytochrome A signals for inhibition of hypocotyl elongation. Plant Cell. 2009 May;21(5):1341-59. doi: 10.1105/tpc.109.067215. Epub 2009 May, 29. PMID:19482971 doi:http://dx.doi.org/10.1105/tpc.109.067215
6. ↑ Sokolova V, Bindics J, Kircher S, Ádám É, Schäfer E, Nagy F, Viczián A. Missense mutation in the amino terminus of phytochrome A disrupts the nuclear import of the photoreceptor. Plant Physiol. 2012 Jan;158(1):107-18. PMID:21969386 doi:10.1104/pp.111.186288
7. ↑ Oh J, Park E, Song K, Bae G, Choi G. PHYTOCHROME INTERACTING FACTOR8 Inhibits Phytochrome A-Mediated Far-Red Light Responses in Arabidopsis. Plant Cell. 2020 Jan;32(1):186-205. PMID:31732705 doi:10.1105/tpc.19.00515