title: Phytochrome-interacting ankyrin repeat protein 2 modulates phytochrome A-mediated PIF3 phosphorylation in light signal transduction.
abstract: Light signals recognized by phytochromes are transduced through interactions between down-stream signaling components. Phytochrome-interacting ankyrin repeat protein 2 (PIA2) was found to interact with phytochrome interacting factor 3 (PIF3), a well-known repressor of plant photomorphogenesis in response to phytochrome-mediated light signalling. Both PIA2 and PIF3 are known to be positive regulators of anthocyanin accumulation in Arabidopsis seedlings under far-red conditions. Thus, we investigated the functional relationship between PIA2 and PIF3 in light signalling. We found that PIA2 suppressed PIF3 phosphorylation by phyA. To elucidate how PIA2 modulates phyA-mediated PIF3 phosphorylation, we generated non-phosphorylation mutants and N-terminal α-helix breaking mutants of PIA2. PIF3 phosphorylation by phyA was not suppressed by α-helix breaking PIA2 mutants. The α-helix breaking mutations also resulted in remarkably decreased interactions between PIA2 and PIF3. However, the non-phosphorylation mutants exhibited no effect on phyA-mediated PIF3 phosphorylation. In addition, decreased anthocyanin accumulation in pia2 knockout plant seedlings was not rescued by overexpression of the α-helix breaking mutant in transgenic plants under far-red conditions. These results suggest that PIA2 modulates phyA-mediated PIF3 phosphorylation by physical interaction with PIF3 and that the secondary structure of the PIA2 N-terminus is important in this modulation.
authors.affiliation: Graduate School of Biotechnology.
authors.forename: Jihye
authors.initials: J
authors.lastname: Yoo
authors.affiliation: Graduate School of Biotechnology shbhoo@khu.ac.kr manhocho@khu.ac.kr.
authors.forename: Man-Ho
authors.initials: MH
authors.lastname: Cho
authors.affiliation: Department of Plant Molecular Systems Biotechnology & Crop Biotech Institute, Kyung Hee University, Yongin, 17104, Korea.
authors.forename: Sang-Won
authors.initials: SW
authors.lastname: Lee
authors.affiliation: Graduate School of Biotechnology shbhoo@khu.ac.kr.
authors.forename: Seong Hee
authors.initials: SH
authors.lastname: Bhoo
mesh_terms: D017089:Ankyrin Repeat; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics / Q000378:metabolism*; D008027:Light; D010766:Phosphorylation / Q000502:physiology; D051942:Phytochrome A / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*
chemical_list: D029681:Arabidopsis Proteins; D051792:Basic Helix-Loop-Helix Proteins; D051942:Phytochrome A; C116162:PIF3 protein, Arabidopsis
keywords: light signal transduction; phytochrome; phytochrome-interacting ankyrin repeat protein 2; phytochrome-interacting factor 3; protein-protein interaction