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

We have used time-resolved absorption and fluorescence spectroscopy with nanosecond resolution to study triplet energy transfer from chlorophylls to carotenoids in a protective process that prevents the formation of reactive singlet oxygen. The light-harvesting complexes studied were isolated from Chromera velia, belonging to a group Alveolata, and Xanthonema debile and Nannochloropsis oceanica, both from Stramenopiles. All three light-harvesting complexes are related to fucoxanthin-chlorophyll protein, but contain only chlorophyll a and no chlorophyll c. In addition, they differ in the carotenoid content. This composition of the complexes allowed us to study the quenching of chlorophyll a triplet states by different carotenoids in a comparable environment. The triplet states of chlorophylls bound to the light-harvesting complexes were quenched by carotenoids with an efficiency close to 100%. Carotenoid triplet states were observed to rise with a ~5 ns lifetime and were spectrally and kinetically homogeneous. The triplet states were formed predominantly on the red-most chlorophylls and were quenched by carotenoids which were further identified or at least spectrally characterized.

• Klíčová slova
• Algae, Energy transfer, Light harvesting, Photoprotection, Photosynthesis, Transient spectroscopy,
• MeSH
• anaerobióza MeSH
• časové faktory MeSH
• chlorofyl metabolismus   MeSH
• fluorescenční spektrometrie MeSH
• fotochemické procesy * MeSH
• Heterokontophyta metabolismus   MeSH
• karotenoidy metabolismus   MeSH
• kinetika MeSH
• proteiny vázající chlorofyl metabolismus   MeSH
• světlosběrné proteinové komplexy metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• chlorofyl MeSH
• karotenoidy MeSH
• proteiny vázající chlorofyl MeSH
• světlosběrné proteinové komplexy MeSH