Photosynthetic membrane organization and role of state transition in cyt, cpII, stt7 and npq mutants of Chlamydomonas reinhardtii.
In Chlamydomonas reinhardtii, cytochrome b6/f and chlorophyll b binding proteins are important in energy distribution between photosystem (PS)II and PSI. In this study, we have used C. reinhardtii mutants deficient in cytochrome b6/f complex (cyt), chlorophyll b binding protein (cpII), non-photochemical quenching (npq) and LHC II kinase (stt7) to study the importance of these proteins in electron transport, phosphorylation, and structural organization of thylakoid supercomplexes under optimum growth conditions. Fast Chl a fluorescence studies have shown that lack of CpII and Cyt b6/f caused reduced photochemical yield (Fv/Fm). The disappearance of I phase in cyt mutant showed that electron transfer from Cyt b6/f to PSI is reduced due to un availability of Q0 site for docking of PQH2 therefore LHC II kinase was unable to phosphorylate LHCII in cyt mutant. Further, blue native gel electrophoresis revealed the differential organization of photosynthetic membrane protein complexes in different mutants. Particularly, LHCII trimerization is more in cyt and stt7 mutants. Also, chemically induced state transition (LHCII phosphorylation) was not observed in cyt mutant, however, all other mutants were similar to that of wild type. Based on our results, we propose that the LHCII trimer accumulation and its organization with other complexes are very important in state transitions.
Department of Plant Sciences, School of Life Sciences, University of Hyderabad, Hyderabad 500046, India.
Sai Kiran
SK
Madireddi
Department of Plant Sciences, School of Life Sciences, University of Hyderabad, Hyderabad 500046, India.
Srilatha
S
Nama
Department of Plant Sciences, School of Life Sciences, University of Hyderabad, Hyderabad 500046, India.
Elsin Raju
ER
Devadasu
Department of Plant Sciences, School of Life Sciences, University of Hyderabad, Hyderabad 500046, India. Electronic address: srgsl@uohyd.ernet.in.
Rajagopal
R
Subramanyam
D016825:Chlamydomonas reinhardtii / Q000166:cytology* / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D002734:Chlorophyll / Q000378:metabolism; D000077194:Chlorophyll A; D061146:Chlorophyll Binding Proteins / Q000235:genetics / Q000378:metabolism; D045346:Cytochrome b6f Complex / Q000235:genetics / Q000378:metabolism; D004734:Energy Metabolism; D045342:Light-Harvesting Protein Complexes / Q000235:genetics / Q000378:metabolism; D050505:Mutant Proteins / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D010641:Phenotype; D010766:Phosphorylation; D010788:Photosynthesis; D045331:Photosystem I Protein Complex / Q000378:metabolism; D045332:Photosystem II Protein Complex / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism; D020524:Thylakoids / Q000378:metabolism*
D061146:Chlorophyll Binding Proteins; D045342:Light-Harvesting Protein Complexes; D050505:Mutant Proteins; D045331:Photosystem I Protein Complex; D045332:Photosystem II Protein Complex; D010940:Plant Proteins; D002734:Chlorophyll; D045346:Cytochrome b6f Complex; D011494:Protein Kinases; C120337:light-harvesting complex II kinase; D000077194:Chlorophyll A
Chl a fluorescence; Cyt b(6)/f; Light harvesting complex; Non photochemical quenching; Photosystems; State transitions