title: Presence of state transitions in the cryptophyte alga Guillardia theta.
abstract: Plants and algae have developed various regulatory mechanisms for optimal delivery of excitation energy to the photosystems even during fluctuating light conditions; these include state transitions as well as non-photochemical quenching. The former process maintains the balance by redistributing antennae excitation between the photosystems, meanwhile the latter by dissipating excessive excitation inside the antennae. In the present study, these mechanisms have been analysed in the cryptophyte alga Guillardia theta. Photoprotective non-photochemical quenching was observed in cultures only after they had entered the stationary growth phase. These cells displayed a diminished overall photosynthetic efficiency, measured as CO2 assimilation rate and electron transport rate. However, in the logarithmic growth phase G. theta cells redistributed excitation energy via a mechanism similar to state transitions. These state transitions were triggered by blue light absorbed by the membrane integrated chlorophyll a/c antennae, and green light absorbed by the lumenal biliproteins was ineffective. It is proposed that state transitions in G. theta are induced by small re-arrangements of the intrinsic antennae proteins, resulting in their coupling/uncoupling to the photosystems in state 1 or state 2, respectively. G. theta therefore represents a chromalveolate algae able to perform state transitions.
authors.affiliation: Department of Chemistry, Umeå University, SE-90187 Umeå, Sweden.
authors.forename: Otilia
authors.initials: O
authors.lastname: Cheregi
authors.affiliation: Institute of Microbiology, Centre Algatech, Laboratory of Photosynthesis, Opatovický Mlýn, Třeboň 379 81, Czech Republic.
authors.forename: Eva
authors.initials: E
authors.lastname: Kotabová
authors.affiliation: Institute of Microbiology, Centre Algatech, Laboratory of Photosynthesis, Opatovický Mlýn, Třeboň 379 81, Czech Republic.
authors.forename: Ondřej
authors.initials: O
authors.lastname: Prášil
authors.affiliation: Department of Chemistry, Umeå University, SE-90187 Umeå, Sweden.
authors.forename: Wolfgang P
authors.initials: WP
authors.lastname: Schröder
authors.affiliation: Institute of Microbiology, Centre Algatech, Laboratory of Photosynthesis, Opatovický Mlýn, Třeboň 379 81, Czech Republic christiane.funk@chem.umu.se kana@alga.cz.
authors.forename: Radek
authors.initials: R
authors.lastname: Kaňa
authors.affiliation: Department of Chemistry, Umeå University, SE-90187 Umeå, Sweden christiane.funk@chem.umu.se kana@alga.cz.
authors.forename: Christiane
authors.initials: C
authors.lastname: Funk
mesh_terms: D002245:Carbon Dioxide / Q000378:metabolism*; D044785:Cryptophyta / Q000254:growth & development / Q000502:physiology*; D004579:Electron Transport; D008027:Light; D055668:Photochemical Processes; D010788:Photosynthesis
chemical_list: D002245:Carbon Dioxide
keywords: Blue/low light adaptation; chlorophyll a/c antenna; cryptophytes; growth stage; non-photochemical quenching; state transitions.