In diatoms, a transthylakoid proton gradient alone is not sufficient to induce a non-photochemical fluorescence quenching.
Non-photochemical fluorescence quenching (NPQ) in diatoms is associated with a xanthophyll cycle involving diadinoxanthin (DD) and its de-epoxidized form, diatoxanthin (DT). In higher plants, an obligatory role of de-epoxidized xanthophylls in NPQ remains controversial and the presence of a transthylakoid proton gradient (DeltapH) alone may induce NPQ. We used inhibitors to alter the amplitude of DeltapH and/or DD de-epoxidation, and coupled NPQ. No DeltapH-dependent quenching was detected in the absence of DT. In diatoms, both DeltapH and DT are required for NPQ. The binding of DT to protonated antenna sites could be obligatory for energy dissipation.
Lavaud
J
J
Laboratoire Organismes Photosynthétiques et Environnement, UMR CNRS 8543, Ecole Normale Supérieure, 46 rue d'Ulm, 75230 Cedex 05, Paris, France. lavaud@biologie.ens.fr
Rousseau
B
B
Etienne
A-L
AL
D002734:Chlorophyll / Q000378:metabolism*; D017377:Diatoms / Q000378:metabolism*; D005453:Fluorescence; D010777:Photochemistry; D017494:Proton Pumps / Q000378:metabolism; D020524:Thylakoids / Q000378:metabolism*; D024341:Xanthophylls / Q000378:metabolism
D017494:Proton Pumps; D024341:Xanthophylls; D002734:Chlorophyll; C033808:diadinoxanthin; C103105:diatoxanthin