title: TOPP4 Regulates the Stability of PHYTOCHROME INTERACTING FACTOR5 during Photomorphogenesis in Arabidopsis.
abstract: In plants, photoreceptors transfer light signals to phytochrome-interacting factors (PIFs), inducing the rapid phosphorylation and degradation of PIFs to promote photomorphogenesis. However, the phosphatase responsible for PIF dephosphorylation remains unknown. In this study, we identified a type 1 protein phosphatase, TOPP4, that is essential for PIF5 protein stability in Arabidopsis (Arabidopsis thaliana). Compared with the wild type, the dominant-negative mutant, topp4-1, displayed reduced hypocotyl length and larger apical hook and cotyledon opening angle under red light. Overexpression of topp4-1 in the wild type led to defects that were similar to those in the topp4-1 mutant. Red light induced phytochrome B (phyB)-dependent TOPP4 expression in hypocotyls. The topp4-1 mutation weakened the closed cotyledon angle of phyB-9 and phyA-211 phyB-9, while overexpression of TOPP4 significantly repressed the short hypocotyls of phyB-green fluorescent protein seedlings, indicating that TOPP4 and phyB function in an antagonistic way during photomorphogenesis. Protein interaction assays and phosphorylation studies demonstrate that TOPP4 interacts directly with PIF5 and dephosphorylates it. Furthermore, TOPP4 inhibits the red light-induced ubiquitination and degradation of PIF5. These findings demonstrate that dephosphorylation of PIF5 by TOPP4 inhibits its ubiquitin-mediated degradation during photomorphogenesis. These data outline a novel phytochrome signaling mechanism by which TOPP4-mediated dephosphorylation of PIF5 attenuates phytochrome-dependent light responses.
authors.affiliation: Ministry of Education Key Laboratory of Cell Activities and Stress Adaptations, School of Life Sciences, Lanzhou University, Lanzhou 730000, China.
authors.forename: Jing
authors.identifier: http://orcid.org/0000-0001-8340-0461
authors.initials: J
authors.lastname: Yue
authors.affiliation: Ministry of Education Key Laboratory of Cell Activities and Stress Adaptations, School of Life Sciences, Lanzhou University, Lanzhou 730000, China.
authors.forename: Qianqian
authors.initials: Q
authors.lastname: Qin
authors.affiliation: Ministry of Education Key Laboratory of Cell Activities and Stress Adaptations, School of Life Sciences, Lanzhou University, Lanzhou 730000, China.
authors.forename: Siyuan
authors.initials: S
authors.lastname: Meng
authors.affiliation: Ministry of Education Key Laboratory of Cell Activities and Stress Adaptations, School of Life Sciences, Lanzhou University, Lanzhou 730000, China.
authors.forename: Huiting
authors.identifier: http://orcid.org/0000-0002-6436-2380
authors.initials: H
authors.lastname: Jing
authors.affiliation: Ministry of Education Key Laboratory of Cell Activities and Stress Adaptations, School of Life Sciences, Lanzhou University, Lanzhou 730000, China.
authors.forename: Xiaoping
authors.identifier: http://orcid.org/0000-0002-8391-0258
authors.initials: X
authors.lastname: Gou
authors.affiliation: Ministry of Education Key Laboratory of Cell Activities and Stress Adaptations, School of Life Sciences, Lanzhou University, Lanzhou 730000, China.
authors.forename: Jia
authors.initials: J
authors.lastname: Li
authors.affiliation: Ministry of Education Key Laboratory of Cell Activities and Stress Adaptations, School of Life Sciences, Lanzhou University, Lanzhou 730000, China housw@lzu.edu.cn.
authors.forename: Suiwen
authors.initials: S
authors.lastname: Hou
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics / Q000378:metabolism*; D017343:Genes, Plant; D018546:Hypocotyl / Q000254:growth & development / Q000378:metabolism / Q000528:radiation effects; D008027:Light; D008954:Models, Biological; D009154:Mutation; D010749:Phosphoprotein Phosphatases / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D051939:Phytochrome B / Q000378:metabolism*; D030821:Plants, Genetically Modified; D055550:Protein Stability / Q000528:radiation effects; D059748:Proteolysis / Q000528:radiation effects; D015398:Signal Transduction; D054875:Ubiquitination / Q000528:radiation effects
chemical_list: D029681:Arabidopsis Proteins; D051792:Basic Helix-Loop-Helix Proteins; D010749:Phosphoprotein Phosphatases; D051939:Phytochrome B; C116162:PIF3 protein, Arabidopsis; C497729:PIF5 protein, Arabidopsis; C000604153:type-one protein phosphatase TOPP4, Arabidopsis