title: Significance of the photosystem II core phosphatase PBCP for plant viability and protein repair in thylakoid membranes.
abstract: PSII undergoes photodamage, which results in photoinhibition-the light-induced loss of photosynthetic activity. The main target of damage in PSII is the reaction center protein D1, which is buried in the massive 1.4 MDa PSII holocomplex. Plants have evolved a PSII repair cycle that degrades the damaged D1 subunit and replaces it with a newly synthesized copy. PSII core proteins, including D1, are phosphorylated in high light. This phosphorylation is important for the mobilization of photoinhibited PSII from stacked grana thylakoids to the repair machinery in distant unstacked stroma lamellae. It has been recognized that the degradation of the damaged D1 is more efficient after its dephosphorylation by a protein phosphatase. Recently a protein phosphatase 2C (PP2C)-type PSII core phosphatase (PBCP) has been discovered, which is involved in the dephosphorylation of PSII core proteins. Its role in PSII repair, however, is unknown. Using a range of spectroscopic and biochemical techniques, we report that the inactivation of the PBCP gene affects the growth characteristic of plants, with a decreased biomass and altered PSII functionality. PBCP mutants show increased phosphorylation of core subunits in dark and photoinhibitory conditions and a diminished degradation of the D1 subunit. Our results on D1 turnover in PBCP mutants suggest that dephosphorylation of PSII subunits is required for efficient D1 degradation.
authors.affiliation: Institute of Biological Chemistry, Washington State University, Pullman, WA 99164-6340, USA.
authors.forename: Sujith
authors.initials: S
authors.lastname: Puthiyaveetil
authors.affiliation: Institute of Biological Chemistry, Washington State University, Pullman, WA 99164-6340, USA.
authors.forename: Timothy
authors.initials: T
authors.lastname: Woodiwiss
authors.affiliation: Institute of Biological Chemistry, Washington State University, Pullman, WA 99164-6340, USA.
authors.forename: Ryan
authors.initials: R
authors.lastname: Knoerdel
authors.affiliation: Institute of Biological Chemistry, Washington State University, Pullman, WA 99164-6340, USA.
authors.forename: Ahmad
authors.initials: A
authors.lastname: Zia
authors.affiliation: Institute of Biological Chemistry, Washington State University, Pullman, WA 99164-6340, USA.
authors.forename: Magnus
authors.initials: M
authors.lastname: Wood
authors.affiliation: Institute of Biological Chemistry, Washington State University, Pullman, WA 99164-6340, USA.
authors.forename: Ricarda
authors.initials: R
authors.lastname: Hoehner
authors.affiliation: Institute of Biological Chemistry, Washington State University, Pullman, WA 99164-6340, USA kirchhh@wsu.edu.
authors.forename: Helmut
authors.initials: H
authors.lastname: Kirchhoff
mesh_terms: D020121:5' Untranslated Regions / Q000235:genetics; D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development / Q000378:metabolism* / Q000528:radiation effects; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D018533:Biomass; D003624:Darkness; D018506:Gene Expression Regulation, Plant; D055786:Gene Knockout Techniques; D008027:Light; D016254:Mutagenesis, Insertional; D010641:Phenotype; D010749:Phosphoprotein Phosphatases / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D010788:Photosynthesis; D045332:Photosystem II Protein Complex / Q000235:genetics / Q000378:metabolism*; D011523:Protoplasts; D036226:Seedlings; D020524:Thylakoids / Q000378:metabolism*
chemical_list: D020121:5' Untranslated Regions; D029681:Arabidopsis Proteins; D045332:Photosystem II Protein Complex; D010749:Phosphoprotein Phosphatases; C576571:photosystem II phosphatase, Arabidopsis
keywords: PBCP; PSII repair cycle; Photoinhibition; STN8