Light-Harvesting Complex Stress-Related Proteins Catalyze Excess Energy Dissipation in Both Photosystems of Physcomitrella patens.
Two LHC-like proteins, Photosystem II Subunit S (PSBS) and Light-Harvesting Complex Stress-Related (LHCSR), are essential for triggering excess energy dissipation in chloroplasts of vascular plants and green algae, respectively. The mechanism of quenching was studied in Physcomitrella patens, an early divergent streptophyta (including green algae and land plants) in which both proteins are active. PSBS was localized in grana together with photosystem II (PSII), but LHCSR was located mainly in stroma-exposed membranes together with photosystem I (PSI), and its distribution did not change upon high-light treatment. The quenched conformation can be preserved by rapidly freezing the high-light-treated tissues in liquid nitrogen. When using green fluorescent protein as an internal standard, 77K fluorescence emission spectra on isolated chloroplasts allowed for independent assessment of PSI and PSII fluorescence yield. Results showed that both photosystems underwent quenching upon high-light treatment in the wild type in contrast to mutants depleted of LHCSR, which lacked PSI quenching. Due to the contribution of LHCII, P. patens had a PSI antenna size twice as large with respect to higher plants. Thus, LHCII, which is highly abundant in stroma membranes, appears to be the target of quenching by LHCSR.
Department of Biotechnology, University of Verona, 37134 Verona, Italy.
Alberta
http://orcid.org/0000-0001-8373-7638
A
Pinnola
Department of Biotechnology, University of Verona, 37134 Verona, Italy.
Stefano
S
Cazzaniga
Department of Biotechnology, University of Verona, 37134 Verona, Italy.
Alessandro
http://orcid.org/0000-0003-4818-7778
A
Alboresi
Department of Biological Chemistry, Weizmann Institute of Science, Rehovot 76100, Israel.
Reinat
R
Nevo
Electron Microscopy Unit, Weizmann Institute of Science, Rehovot 76100, Israel.
Smadar
S
Levin-Zaidman
Department of Biological Chemistry, Weizmann Institute of Science, Rehovot 76100, Israel.
Ziv
Z
Reich
Department of Biotechnology, University of Verona, 37134 Verona, Italy roberto.bassi@univr.it.
Roberto
http://orcid.org/0000-0002-4140-8446
R
Bassi
D019068:Bryopsida / Q000187:drug effects / Q000378:metabolism* / Q000528:radiation effects / Q000648:ultrastructure; D002384:Catalysis / Q000187:drug effects; D002734:Chlorophyll / Q000378:metabolism; D002736:Chloroplasts / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D004072:Digitonin / Q000494:pharmacology; D005960:Glucosides / Q000494:pharmacology; D008027:Light; D045342:Light-Harvesting Protein Complexes / Q000378:metabolism*; D021962:Membrane Microdomains / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects; D055668:Photochemical Processes / Q000187:drug effects; D045331:Photosystem I Protein Complex / Q000378:metabolism*; D045332:Photosystem II Protein Complex / Q000378:metabolism*; D010940:Plant Proteins / Q000378:metabolism*; D013050:Spectrometry, Fluorescence; D013312:Stress, Physiological / Q000187:drug effects / Q000528:radiation effects; D013816:Thermodynamics; D020524:Thylakoids / Q000378:metabolism / Q000528:radiation effects / Q000648:ultrastructure
D005960:Glucosides; D045342:Light-Harvesting Protein Complexes; D045331:Photosystem I Protein Complex; D045332:Photosystem II Protein Complex; D010940:Plant Proteins; D002734:Chlorophyll; C040358:dodecyl maltoside; D004072:Digitonin