Characterization of the photosynthetic apparatus of the Eustigmatophycean Nannochloropsis gaditana: Evidence of convergent evolution in the supramolecular organization of photosystem I

• Published in: Biochimica et biophysica acta 2014-02, Vol.1837 (2), p.306-314
• Main Authors: Basso, Stefania, Simionato, Diana, Gerotto, Caterina, Segalla, Anna, Giacometti, Giorgio M., Morosinotto, Tomas
• Format: Article
• Language: English
• Subjects: Absorption; Carotenoids - metabolism; Centrifugation, Density Gradient; Evolution, Molecular; Heterokonta; Light-harvesting complex; Light-Harvesting Protein Complexes - metabolism; Peptides - metabolism; Photosynthesis; Photosynthetic apparatus; Photosystem; Photosystem I Protein Complex - metabolism; Photosystem II Protein Complex - metabolism; Protein Binding; Spectrometry, Fluorescence; Stramenopiles - metabolism; Thylakoid; Xanthophylls - metabolism
• ISSN: 0005-2728; 0006-3002; 1879-2650
• DOI: 10.1016/j.bbabio.2013.11.019

Nannochloropsis gaditana belongs to Eustigmatophyceae, a class of eukaryotic algae resulting from a secondary endosymbiotic event. Species of this class have been poorly characterized thus far but are now raising increasing interest in the scientific community because of their possible application in biofuel production. Nannochloropsis species have a peculiar photosynthetic apparatus characterized by the presence of only chlorophyll a, with violaxanthin and vaucheriaxanthin esters as the most abundant carotenoids. In this study, the photosynthetic apparatus of this species was analyzed by purifying the thylakoids and isolating the different pigment-binding complexes upon mild solubilization. The results from the biochemical and spectroscopic characterization showed that the photosystem II antenna is loosely bound to the reaction center, whereas the association is stronger in photosystem I, with the antenna-reaction center super-complexes surviving purification. Such a supramolecular organization was found to be conserved in photosystem I from several other photosynthetic eukaryotes, even though these taxa are evolutionarily distant. A hypothesis on the possible selective advantage of different associations of the antenna complexes of photosystems I and II is discussed. [Display omitted] •Characterization of Nannochloropsis gaditana photosynthetic apparatus•Photosystem I antenna-reaction center supercomplexes survive purification.•Photosystem I supramolecular organization is conserved in the evolution.•Evidences for convergent evolution in photosystem I antenna in eukaryotes