title: Zeaxanthin binds to light-harvesting complex stress-related protein to enhance nonphotochemical quenching in Physcomitrella patens.
abstract: Nonphotochemical quenching (NPQ) dissipates excess energy to protect the photosynthetic apparatus from excess light. The moss Physcomitrella patens exhibits strong NPQ by both algal-type light-harvesting complex stress-related (LHCSR)-dependent and plant-type S subunit of Photosystem II (PSBS)-dependent mechanisms. In this work, we studied the dependence of NPQ reactions on zeaxanthin, which is synthesized under light stress by violaxanthin deepoxidase (VDE) from preexisting violaxanthin. We produced vde knockout (KO) plants and showed they underwent a dramatic reduction in thermal dissipation ability and enhanced photoinhibition in excess light conditions. Multiple mutants (vde lhcsr KO and vde psbs KO) showed that zeaxanthin had a major influence on LHCSR-dependent NPQ, in contrast with previous reports in Chlamydomonas reinhardtii. The PSBS-dependent component of quenching was less dependent on zeaxanthin, despite the near-complete violaxanthin to zeaxanthin exchange in LHC proteins. Consistent with this, we provide biochemical evidence that native LHCSR protein binds zeaxanthin upon excess light stress. These findings suggest that zeaxanthin played an important role in the adaptation of modern plants to the enhanced levels of oxygen and excess light intensity of land environments.
authors.affiliation: Dipartimento di Biotecnologie, Università degli Studi di Verona, 37134 Verona, Italy.
authors.forename: Alberta
authors.initials: A
authors.lastname: Pinnola
authors.forename: Luca
authors.initials: L
authors.lastname: Dall'Osto
authors.forename: Caterina
authors.initials: C
authors.lastname: Gerotto
authors.forename: Tomas
authors.initials: T
authors.lastname: Morosinotto
authors.forename: Roberto
authors.initials: R
authors.lastname: Bassi
authors.forename: Alessandro
authors.initials: A
authors.lastname: Alboresi
mesh_terms: D000222:Adaptation, Physiological; D053898:Biosynthetic Pathways; D019068:Bryopsida / Q000235:genetics / Q000502:physiology* / Q000528:radiation effects; D002734:Chlorophyll / Q000378:metabolism; D055786:Gene Knockout Techniques; D008027:Light; D045342:Light-Harvesting Protein Complexes / Q000378:metabolism* / Q000528:radiation effects; D045332:Photosystem II Protein Complex / Q000378:metabolism / Q000528:radiation effects; D020524:Thylakoids / Q000378:metabolism; D024341:Xanthophylls / Q000378:metabolism; D065146:Zeaxanthins / Q000378:metabolism*
chemical_list: D045342:Light-Harvesting Protein Complexes; D045332:Photosystem II Protein Complex; D024341:Xanthophylls; D065146:Zeaxanthins; D002734:Chlorophyll; C005613:violaxanthin