title: Role of red carotenoids in photoprotection during winter acclimation in Buxus sempervirens leaves.
abstract: The red leaf coloration of several plant species during autumn and winter is due to the synthesis of phenolic compounds such as anthocyanins or red carotenoids. The latter occur very rarely and are non-ubiquitous and taxonomically restricted compounds. The present study shows that the leaves of common box ( Buxus sempervirens L.) accumulate red carotenoids (eschscholtzxanthin, monoanhydroeschscholtzxanthin, anhydroeschscholtzxanthin) as a response to photoinhibitory conditions during winter acclimation. These compounds are produced in a coordinated manner with the operation of other photoprotective systems: accumulation and sustained deepoxidation of VAZ pigments with a concomitant decrease in maximal photochemical efficiency, accumulation of alpha-tocopherol and a gradual decrease on chlorophyll content. All these processes were reversed when the photosynthetic tissues were transferred from photoinhibitory winter conditions to room temperature for 9 days. Buxus leaves showed a large degree of phenotype variation in the degree of reddening, ranging from green to orange. The differences in colour pattern were mainly due to differences in the accumulation of red carotenoids and xanthophyll esters. Red pigments were mainly anhydroeschscholtzxanthin and esters of eschscholtzxanthin. Conversely to fruit or petal chromoplasts, the plastids of red leaves in this species are not the terminal differentiated state but are able to redifferentiate again to chloroplasts. Their photoprotective role during winter as a light screen system or as antioxidants, in a similar way to other red pigments, and their implications on the wide ecological tolerance of this evergreen species are discussed.
authors.affiliation: Department of Plant Biology and Ecology, Universidad del País Vasco-EHU, Bilbao, Spain.
authors.forename: K
authors.initials: K
authors.lastname: Hormaetxe
authors.forename: A
authors.initials: A
authors.lastname: Hernández
authors.forename: J M
authors.initials: JM
authors.lastname: Becerril
authors.forename: J I
authors.initials: JI
authors.lastname: García-Plazaola
mesh_terms: D000064:Acclimatization / Q000502:physiology* / Q000528:radiation effects; D031235:Buxus / Q000254:growth & development / Q000378:metabolism* / Q000528:radiation effects; D002734:Chlorophyll / Q000378:metabolism; D002736:Chloroplasts / Q000378:metabolism / Q000528:radiation effects; D003080:Cold Temperature; D008027:Light; D015394:Molecular Structure; D010641:Phenotype; D045322:Photosynthetic Reaction Center Complex Proteins / Q000378:metabolism* / Q000528:radiation effects; D010858:Pigmentation / Q000528:radiation effects; D018515:Plant Leaves / Q000254:growth & development / Q000378:metabolism* / Q000528:radiation effects; D024341:Xanthophylls / Q000737:chemistry / Q000378:metabolism* / Q000528:radiation effects; D024502:alpha-Tocopherol / Q000378:metabolism
chemical_list: D045322:Photosynthetic Reaction Center Complex Proteins; D024341:Xanthophylls; D002734:Chlorophyll; D024502:alpha-Tocopherol