CBC Department Special Seminar: "Photosynthesis in the Far-Red"

Presenter:

Dr. Christopher Gisriel

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Abstract:

The light reactions of photosynthesis are driven by pigment-protein complexes that convert sunlight’s energy into chemical energy.

These complexes therefore serve as the gateway for energy into our biosphere and define Earth’s atmospheric and geological composition. Cyanobacteria contribute greatly to global photosynthesis and exhibit profound diversity, being found in almost every imaginable habitat. Most photosynthetic organisms, including cyanobacteria, require light in the visible region of the solar spectrum (400-700 nm) to drive photosynthesis. However, it was recently discovered that when grown in shaded environments, some cyanobacteria alter their pigment-protein complexes so that far-red light (700-800 nm) can drive photochemistry, a process called far-red light photo acclimation. Revealing the molecular basis of this process may allow for the engineering of crops to do the same, potentially increasing yield. To achieve this, we have solved molecular structures of the protein complexes in cyanobacteria that are adapted to absorb far-red light using cryo-electron microscopy. Identifying the differences between the standard protein complexes and those adapted to absorb far-red light required the development of novel techniques to differentiate cofactors. These investigations have set the stage for leveraging this knowledge to engineer crop enhancement and to design artificial photosystems. Furthermore, they have revealed the diversity of light-harvesting strategies in nature that require the fine balancing of resource availability, environmental plasticity, and efficiency.