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.

Faculty of Science University of South Bohemia Branišovská 1760 370 05 České Budějovice Czech Republic Biology Centre The Czech Academy of Sciences Branišovská 31 370 05 České Budějovice Czech Republic

Faculty of Science University of South Bohemia Branišovská 1760 370 05 České Budějovice Czech Republic Institute of Microbiology The Czech Academy of Sciences Opatovický mlýn 379 81 Třeboň Czech Republic

PSI spol s r o Drásov 470 664 24 Drásov Czech Republic

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