Photosynthetic organisms harvest light for energy. Some eukaryotic algae have specialized in harvesting far-red light by tuning chlorophyll a absorption through a mechanism still to be elucidated. Here, we combined optically detected magnetic resonance and pulsed electron paramagnetic resonance measurements on red-adapted light-harvesting complexes, rVCP, isolated from the freshwater eustigmatophyte alga Trachydiscus minutus to identify the location of the pigments responsible for this remarkable adaptation. The pigments have been found to belong to an excitonic cluster of chlorophylls a at the core of the complex, close to the central carotenoids in L1/L2 sites. A pair of structural features of the Chl a403/a603 binding site, namely the histidine-to-asparagine substitution in the magnesium-ligation residue and the small size of the amino acid at the i-4 position, resulting in a [A/G]xxxN motif, are proposed to be the origin of this trait. Phylogenetic analysis of various eukaryotic red antennae identified several potential LHCs that could share this tuning mechanism. This knowledge of the red light acclimation mechanism in algae is a step towards rational design of algal strains in order to enhance light capture and efficiency in large-scale biotechnology applications.

• MeSH
• chlorofyl a * metabolismus   chemie   MeSH
• chlorofyl metabolismus   MeSH
• elektronová paramagnetická rezonance MeSH
• fylogeneze MeSH
• světlo MeSH
• světlosběrné proteinové komplexy * metabolismus   genetika   chemie   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• chlorofyl a * MeSH
• chlorofyl MeSH
• světlosběrné proteinové komplexy * MeSH

Survival of phototrophic organisms depends on their ability to collect and convert enough light energy to support their metabolism. Phototrophs can extend their absorption cross section by using diverse pigments and by tuning the properties of these pigments via pigment-pigment and pigment-protein interaction. It is well known that some cyanobacteria can grow in heavily shaded habitats by utilizing far-red light harvested with far-red-absorbing chlorophylls d and f. We describe a red-shifted light-harvesting system based on chlorophyll a from a freshwater eustigmatophyte alga Trachydiscus minutus (Eustigmatophyceae, Goniochloridales). A comprehensive characterization of the photosynthetic apparatus of T. minutus is presented. We show that thylakoid membranes of T. minutus contain light-harvesting complexes of several sizes differing in the relative amount of far-red chlorophyll a forms absorbing around 700 nm. The pigment arrangement of the major red-shifted light-harvesting complex is similar to that of the red-shifted antenna of a marine alveolate alga Chromera velia. Evolutionary aspects of the algal far-red light-harvesting complexes are discussed. The presence of these antennas in eustigmatophyte algae opens up new ways to modify organisms of this promising group for effective use of far-red light in mass cultures.

• Klíčová slova
• Chromatic acclimation, Eustigmatophyta, Light-harvesting protein, Oligomeric LHC, Red-shifted LHC, Violaxanthin,
• MeSH
• biologické pigmenty metabolismus   MeSH
• diuron MeSH
• fluorescenční spektrometrie MeSH
• Heterokontophyta metabolismus   účinky záření   MeSH
• membránové proteiny metabolismus   MeSH
• sladká voda * MeSH
• světlo * MeSH
• světlosběrné proteinové komplexy metabolismus   MeSH
• teplota MeSH
• tylakoidy metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• biologické pigmenty MeSH
• diuron MeSH
• membránové proteiny MeSH
• světlosběrné proteinové komplexy MeSH