title: In Vivo Identification of Photosystem II Light Harvesting Complexes Interacting with PHOTOSYSTEM II SUBUNIT S.
abstract: Light is the primary energy source for photosynthetic organisms, but in excess, it can generate reactive oxygen species and lead to cell damage. Plants evolved multiple mechanisms to modulate light use efficiency depending on illumination intensity to thrive in a highly dynamic natural environment. One of the main mechanisms for protection from intense illumination is the dissipation of excess excitation energy as heat, a process called nonphotochemical quenching. In plants, nonphotochemical quenching induction depends on the generation of a pH gradient across thylakoid membranes and on the presence of a protein called PHOTOSYSTEM II SUBUNIT S (PSBS). Here, we generated Physcomitrella patens lines expressing histidine-tagged PSBS that were exploited to purify the native protein by affinity chromatography. The mild conditions used in the purification allowed copurifying PSBS with its interactors, which were identified by mass spectrometry analysis to be mainly photosystem II antenna proteins, such as LIGHT-HARVESTING COMPLEX B (LHCB). PSBS interaction with other proteins appears to be promiscuous and not exclusive, although the major proteins copurified with PSBS were components of the LHCII trimers (LHCB3 and LHCBM). These results provide evidence of a physical interaction between specific photosystem II light-harvesting complexes and PSBS in the thylakoids, suggesting that these subunits are major players in heat dissipation of excess energy.
authors.affiliation: Department of Biology (C.G., T.M.) and Department of Biomedical Sciences (C.F., G.A.), University of Padova, 35131 Padova, Italy; andProteomics Center of Padova University, 35129 Padova, Italy (C.F., G.A.).
authors.forename: Caterina
authors.identifier: http://orcid.org/0000-0001-7142-3535
authors.initials: C
authors.lastname: Gerotto
authors.affiliation: Department of Biology (C.G., T.M.) and Department of Biomedical Sciences (C.F., G.A.), University of Padova, 35131 Padova, Italy; andProteomics Center of Padova University, 35129 Padova, Italy (C.F., G.A.).
authors.forename: Cinzia
authors.initials: C
authors.lastname: Franchin
authors.affiliation: Department of Biology (C.G., T.M.) and Department of Biomedical Sciences (C.F., G.A.), University of Padova, 35131 Padova, Italy; andProteomics Center of Padova University, 35129 Padova, Italy (C.F., G.A.).
authors.forename: Giorgio
authors.initials: G
authors.lastname: Arrigoni
authors.affiliation: Department of Biology (C.G., T.M.) and Department of Biomedical Sciences (C.F., G.A.), University of Padova, 35131 Padova, Italy; andProteomics Center of Padova University, 35129 Padova, Italy (C.F., G.A.) tomas.morosinotto@unipd.it.
authors.forename: Tomas
authors.identifier: http://orcid.org/0000-0002-0803-7591
authors.initials: T
authors.lastname: Morosinotto
mesh_terms: D000595:Amino Acid Sequence; D019068:Bryopsida / Q000235:genetics / Q000378:metabolism / Q000528:radiation effects; D002734:Chlorophyll / Q000378:metabolism; D005453:Fluorescence; D015151:Immunoblotting; D008027:Light; D045342:Light-Harvesting Protein Complexes / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D009154:Mutation; D045332:Photosystem II Protein Complex / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D010802:Phylogeny; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D030821:Plants, Genetically Modified; D011485:Protein Binding; D057949:Streptophyta / Q000145:classification / Q000235:genetics / Q000378:metabolism; D020524:Thylakoids / Q000235:genetics / Q000378:metabolism*; D065146:Zeaxanthins / Q000378:metabolism
chemical_list: D045342:Light-Harvesting Protein Complexes; D045332:Photosystem II Protein Complex; D010940:Plant Proteins; D065146:Zeaxanthins; D002734:Chlorophyll