title: Light adaptation of the unicellular red alga, Cyanidioschyzon merolae, probed by time-resolved fluorescence spectroscopy.
abstract: Photosynthetic organisms change the quantity and/or quality of their pigment-protein complexes and the interactions among these complexes in response to light conditions. In the present study, we analyzed light adaptation of the unicellular red alga Cyanidioschyzon merolae, whose pigment composition is similar to that of cyanobacteria because its phycobilisomes (PBS) lack phycoerythrin. C. merolae were grown under different light qualities, and their responses were measured by steady-state absorption, steady-state fluorescence, and picosecond time-resolved fluorescence spectroscopies. Cells were cultivated under four monochromatic light-emitting diodes (blue, green, yellow, and red), and changes in pigment composition and energy transfer were observed. Cells grown under blue and green light increased their relative phycocyanin levels compared with cells cultured under white light. Energy-transfer processes to photosystem I (PSI) were sensitive to yellow and red light. The contribution of direct energy transfer from PBS to PSI increased only under yellow light, while red light induced a reduction in energy transfer from photosystem II to PSI and an increase in energy transfer from light-harvesting chlorophyll protein complex I to PSI. Differences in pigment composition, growth, and energy transfer under different light qualities are discussed.
authors.affiliation: Graduate School of Science, Kobe University, Kobe, 657-8501, Japan.
authors.forename: Yoshifumi
authors.initials: Y
authors.lastname: Ueno
authors.forename: Shimpei
authors.initials: S
authors.lastname: Aikawa
authors.forename: Akihiko
authors.initials: A
authors.lastname: Kondo
authors.forename: Seiji
authors.initials: S
authors.lastname: Akimoto
mesh_terms: D000222:Adaptation, Physiological; D004735:Energy Transfer; D005453:Fluorescence; D008027:Light; D045342:Light-Harvesting Protein Complexes / Q000378:metabolism / Q000528:radiation effects; D045331:Photosystem I Protein Complex / Q000378:metabolism* / Q000528:radiation effects; D045332:Photosystem II Protein Complex / Q000378:metabolism* / Q000528:radiation effects; D045524:Phycobilisomes / Q000378:metabolism* / Q000528:radiation effects; D010798:Phycocyanin / Q000378:metabolism; D010799:Phycoerythrin / Q000378:metabolism; D000461:Rhodophyta / Q000502:physiology* / Q000528:radiation effects; D013050:Spectrometry, Fluorescence
chemical_list: D045342:Light-Harvesting Protein Complexes; D045331:Photosystem I Protein Complex; D045332:Photosystem II Protein Complex; D045524:Phycobilisomes; D010798:Phycocyanin; D010799:Phycoerythrin