The light-harvesting antenna of the diatom Phaeodactylum tricornutum: Evidence for a diadinoxanthin binding sub-complex

Gérard Guglielmi , Johann Lavaud (1, 2) , Bernard Rousseau , Anne-Lise Etienne , Jean Houmard (3) , Alexander V. Ruban (4)

1 LIENSs - LIttoral ENvironnement et Sociétés
2 CNRS - Centre National de la Recherche Scientifique
3 REG - Régulation de l'expression génétique
4 QMUL - Queen Mary University of London

Diatoms differ from higher plants by their antenna system, in terms of both polypeptide and pigment contents. A rapid isolation procedure was designed for the membrane-intrinsic light harvesting complexes (LHC) of the diatom Phaeodactylum tricornutum to establish whether different LHC subcomplexes exist, as well to determine an uneven distribution between them of pigments and polypeptides. Two distinct fractions were separated that contain functional oligomeric complexes. The major and more stable complex (≈ 75% of total polypeptides) carries most of the chlorophyll a, and almost only one type of carotenoid, fucoxanthin. The minor complex, carrying ≈ 10–15% of the total antenna chlorophyll and only a little chlorophyll c, is highly enriched in diadinoxanthin, the main xanthophyll cycle carotenoid. The two complexes also differ in their polypeptide composition, suggesting specialized functions within the antenna. The diadinoxanthin-enriched complex could be where the de-epoxidation of diadinoxanthin into diatoxanthin mostly occurs.

Mots clés: fucoxanthin; Diatom; light-harvesting complex; photoprotection; xanthophyll cycle

Domaines: Biologie végétale

Gérard Guglielmi, Johann Lavaud, Bernard Rousseau, Anne-Lise Etienne, Jean Houmard, et al.. The light-harvesting antenna of the diatom Phaeodactylum tricornutum: Evidence for a diadinoxanthin binding sub-complex. FEBS Journal, 2005, 272, pp.4339-4348. ⟨10.1111/j.1742-4658.2005.04846.x⟩. ⟨hal-01094626⟩