Identification of a photosystem II phosphatase involved in light acclimation in Arabidopsis.
Reversible protein phosphorylation plays a major role in the acclimation of the photosynthetic apparatus to changes in light. Two paralogous kinases phosphorylate subsets of thylakoid membrane proteins. STATE TRANSITION7 (STN7) phosphorylates LHCII, the light-harvesting antenna of photosystem II (PSII), to balance the activity of the two photosystems through state transitions. STN8, which is mainly involved in phosphorylation of PSII core subunits, influences folding of the thylakoid membranes and repair of PSII after photodamage. The rapid reversibility of these acclimatory responses requires the action of protein phosphatases. In a reverse genetic screen, we identified the chloroplast PP2C phosphatase, PHOTOSYSTEM II CORE PHOSPHATASE (PBCP), which is required for efficient dephosphorylation of PSII proteins. Its targets, identified by immunoblotting and mass spectrometry, largely coincide with those of the kinase STN8. The recombinant phosphatase is active in vitro on a synthetic substrate or on isolated thylakoids. Thylakoid folding is affected in the absence of PBCP, while its overexpression alters the kinetics of state transitions. PBCP and STN8 form an antagonistic kinase and phosphatase pair whose substrate specificity and physiological functions are distinct from those of STN7 and the counteracting phosphatase PROTEIN PHOSPHATASE1/THYLAKOID-ASSOCIATED PHOSPHATASE38, but their activities may overlap to some degree.
Department of Botany and Plant Biology, University of Geneva, 30 quai Ernest Ansermet, 1211 Geneva 4, Switzerland.
Iga
I
Samol
Alexey
A
Shapiguzov
Björn
B
Ingelsson
Geoffrey
G
Fucile
Michèle
M
Crèvecoeur
Alexander V
AV
Vener
Jean-David
JD
Rochaix
Michel
M
Goldschmidt-Clermont
D000064:Acclimatization; D017360:Arabidopsis / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002736:Chloroplasts / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D008027:Light; D045342:Light-Harvesting Protein Complexes / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D010749:Phosphoprotein Phosphatases / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D045332:Photosystem II Protein Complex / Q000378:metabolism*; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism; D000071636:Protein Phosphatase 2C; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D060431:Thylakoid Membrane Proteins / Q000235:genetics / Q000378:metabolism
D029681:Arabidopsis Proteins; D045342:Light-Harvesting Protein Complexes; D045332:Photosystem II Protein Complex; D011994:Recombinant Proteins; D060431:Thylakoid Membrane Proteins; D011494:Protein Kinases; C120337:light-harvesting complex II kinase; C504925:STN8 protein, Arabidopsis; D010749:Phosphoprotein Phosphatases; D000071636:Protein Phosphatase 2C; C576571:photosystem II phosphatase, Arabidopsis