title: Physcomitrella patens mutants affected on heat dissipation clarify the evolution of photoprotection mechanisms upon land colonization.
abstract: Light is the source of energy for photosynthetic organisms; when in excess, however, it also drives the formation of reactive oxygen species and, consequently, photoinhibition. Plants and algae have evolved mechanisms to regulate light harvesting efficiency in response to variable light intensity so as to avoid oxidative damage. Nonphotochemical quenching (NPQ) consists of the rapid dissipation of excess excitation energy as heat. Although widespread among oxygenic photosynthetic organisms, NPQ shows important differences in its machinery. In land plants, such as Arabidopsis thaliana, NPQ depends on the presence of PSBS, whereas in the green alga Chlamydomonas reinhardtii it requires a different protein called LHCSR. In this work, we show that both proteins are present in the moss Physcomitrella patens. By generating KO mutants lacking PSBS and/or LHCSR, we also demonstrate that both gene products are active in NPQ. Plants lacking both proteins are more susceptible to high light stress than WT, implying that they are active in photoprotection. These results suggest that NPQ is a fundamental mechanism for survival in excess light and that upon land colonization, photosynthetic organisms evolved a unique mechanism for excess energy dissipation before losing the ancestral one found in algae.
authors.affiliation: Dipartimento di Biotecnologie, Università di Verona, 37134 Verona, Italy.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Alboresi
authors.forename: Caterina
authors.initials: C
authors.lastname: Gerotto
authors.forename: Giorgio M
authors.initials: GM
authors.lastname: Giacometti
authors.forename: Roberto
authors.initials: R
authors.lastname: Bassi
authors.forename: Tomas
authors.initials: T
authors.lastname: Morosinotto
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D005075:Biological Evolution; D019068:Bryopsida / Q000235:genetics* / Q000378:metabolism*; D016825:Chlamydomonas reinhardtii / Q000235:genetics / Q000378:metabolism; D017931:DNA Primers / Q000235:genetics; D055786:Gene Knockout Techniques; D017343:Genes, Plant; D006358:Hot Temperature; D008027:Light; D009154:Mutation; D010788:Photosynthesis / Q000235:genetics / Q000502:physiology; D045322:Photosynthetic Reaction Center Complex Proteins / Q000235:genetics / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D013045:Species Specificity; D013312:Stress, Physiological
chemical_list: D017931:DNA Primers; D045322:Photosynthetic Reaction Center Complex Proteins; D010940:Plant Proteins