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

In oxygenic photosynthesis the initial photochemical processes are carried out by photosystem I (PSI) and II (PSII). Although subunit composition varies between cyanobacterial and plastid photosystems, the core structures of PSI and PSII are conserved throughout photosynthetic eukaryotes. So far, the photosynthetic complexes have been characterised in only a small number of organisms. We performed in silico and biochemical studies to explore the organization and evolution of the photosynthetic apparatus in the chromerids Chromera velia and Vitrella brassicaformis, autotrophic relatives of apicomplexans. We catalogued the presence and location of genes coding for conserved subunits of the photosystems as well as cytochrome b6f and ATP synthase in chromerids and other phototrophs and performed a phylogenetic analysis. We then characterised the photosynthetic complexes of Chromera and Vitrella using 2D gels combined with mass-spectrometry and further analysed the purified Chromera PSI. Our data suggest that the photosynthetic apparatus of chromerids underwent unique structural changes. Both photosystems (as well as cytochrome b6f and ATP synthase) lost several canonical subunits, while PSI gained one superoxide dismutase (Vitrella) or two superoxide dismutases and several unknown proteins (Chromera) as new regular subunits. We discuss these results in light of the extraordinarily efficient photosynthetic processes described in Chromera.

• MeSH
• Alveolata genetika   fyziologie   MeSH
• delece genu MeSH
• fotosyntéza genetika   fyziologie   MeSH
• fotosystém I (proteinový komplex) genetika   izolace a purifikace   fyziologie   MeSH
• fylogeneze MeSH
• hmotnostní spektrometrie MeSH
• molekulární evoluce MeSH
• superoxiddismutasa metabolismus   MeSH
• tylakoidy metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• fotosystém I (proteinový komplex) MeSH
• superoxiddismutasa MeSH