title: The PsbP protein is required for photosystem II complex assembly/stability and photoautotrophy in Arabidopsis thaliana.
abstract: Interfering RNA was used to suppress the expression of the genes At1g06680 and At2g30790 in Arabidopsis thaliana, which encode the PsbP-1 and PsbP-2 proteins, respectively, of photosystem II (PS II). A phenotypic series of transgenic plants was recovered that expressed intermediate and low amounts of PsbP. Chlorophyll fluorescence induction and Q(A)(-) decay kinetics analyses were performed. Decreasing amounts of expressed PsbP protein led to the progressive loss of variable fluorescence and a marked decrease in the fluorescence quantum yield (F(V)/F(M)). This was primarily due to the loss of the J to I transition. Analysis of the fast fluorescence rise kinetics indicated no significant change in the number of PS II(beta) centers present in the mutants. Analysis of Q(A)(-) decay kinetics in the absence of 3-(3,4-dichlorophenyl)-1,1-dimethylurea indicated a defect in electron transfer from Q(A)(-) to Q(B), whereas experiments performed in the presence of this herbicide indicated that charge recombination between Q(A)(-) and the oxygen-evolving complex was seriously retarded in the plants that expressed low amounts of the PsbP protein. These results demonstrate that the amount of functional PS II reaction centers is compromised in the plants that exhibited intermediate and low amounts of the PsbP protein. Plants that lacked detectable PsbP were unable to survive in the absence of sucrose, indicating that the PsbP protein is required for photoautotrophy. Immunological analysis of the PS II protein complement indicated that significant losses of the CP47 and D2 proteins, and intermediate losses of the CP43 and D1 proteins, occurred in the absence of the PsbP protein. This demonstrates that the extrinsic protein PsbP is required for PS II core assembly/stability.
authors.affiliation: Division of Biochemistry and Molecular Biology, Department of Biological Sciences, Louisiana State University, Baton Rouge, Louisiana 70803, USA.
authors.forename: Xiaoping
authors.initials: X
authors.lastname: Yi
authors.forename: Stefan R
authors.initials: SR
authors.lastname: Hargett
authors.forename: Haijun
authors.initials: H
authors.lastname: Liu
authors.forename: Laurie K
authors.initials: LK
authors.lastname: Frankel
authors.forename: Terry M
authors.initials: TM
authors.lastname: Bricker
mesh_terms: D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000502:physiology*; D052818:Autotrophic Processes; D002734:Chlorophyll / Q000737:chemistry; D007700:Kinetics; D008856:Microscopy, Fluorescence; D009154:Mutation; D010100:Oxygen / Q000737:chemistry; D045332:Photosystem II Protein Complex / Q000737:chemistry / Q000502:physiology*; D018515:Plant Leaves / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics* / Q000502:physiology*; D030821:Plants, Genetically Modified / Q000378:metabolism; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000378:metabolism; D013050:Spectrometry, Fluorescence; D020524:Thylakoids / Q000737:chemistry
chemical_list: D029681:Arabidopsis Proteins; D045332:Photosystem II Protein Complex; D010940:Plant Proteins; C523316:PsbP-1 protein, Arabidopsis; C523317:PsbP-2 protein, Arabidopsis; D034741:RNA, Small Interfering; D002734:Chlorophyll; D010100:Oxygen