title: Deregulated chlorophyll b synthesis reduces the energy transfer rate between photosynthetic pigments and induces photodamage in Arabidopsis thaliana.
abstract: Chl b is one of the major light-harvesting pigments in land plants. The synthesis of Chl b is strictly regulated in response to light conditions in order to control the antenna size of photosystems. Regulation of Chl b also affects its distribution as it occurs preferentially in the peripheral antenna complexes. However, it has not been experimentally shown how plants respond to environmental conditions when they accumulate excess Chl b. Previously, we produced an Arabidopsis transgenic plant (referred to as the BC plant) in which Chl b biosynthesis was enhanced. In this study, we analyzed the photosynthetic properties and genome-wide gene expression in this plant under high light conditions in order to understand the effects of deregulated Chl b biosynthesis. The energy transfer rates between Chl a molecules in PSII decreased and H(2)O(2) accumulated extensively in the BC plant. Microarray analysis revealed that a group of genes involved in anthocyanin biosynthesis was down-regulated and that another group of genes, reported to be sensitive to H(2)O(2), was up-regulated in the BC plant. We also found that anthocyanin levels were low, which was consistent with the results of the microarray analysis. These results indicate that deregulation of Chl b caused severe photodamage and altered gene expression profiles under strong illumination. The importance of the regulation of Chl b synthesis is discussed in relation to the correct localization of Chl b and gene expression.
authors.affiliation: Institute of Low Temperature Science, Hokkaido University, N19 W8, Kita-ku, Sapporo, 060-0819 Japan.
authors.forename: Yasuhito
authors.initials: Y
authors.lastname: Sakuraba
authors.forename: Makio
authors.initials: M
authors.lastname: Yokono
authors.forename: Seiji
authors.initials: S
authors.lastname: Akimoto
authors.forename: Ryouichi
authors.initials: R
authors.lastname: Tanaka
authors.forename: Ayumi
authors.initials: A
authors.lastname: Tanaka
mesh_terms: D000872:Anthocyanins / Q000096:biosynthesis; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism* / Q000528:radiation effects; D002734:Chlorophyll / Q000096:biosynthesis*; D004735:Energy Transfer; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D006861:Hydrogen Peroxide / Q000378:metabolism; D008027:Light; D020411:Oligonucleotide Array Sequence Analysis; D010788:Photosynthesis / Q000502:physiology*; D045332:Photosystem II Protein Complex / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000235:genetics / Q000378:metabolism
chemical_list: D000872:Anthocyanins; D045332:Photosystem II Protein Complex; D002734:Chlorophyll; C037184:chlorophyll b; D006861:Hydrogen Peroxide