| Autor: |
Andrew SM; Department of Earth, Marine, and Environmental Sciences, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599., Moreno CM; Department of Earth, Marine, and Environmental Sciences, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599., Plumb K; Department of Marine Sciences, University of Georgia, Athens, GA 30602., Hassanzadeh B; Department of Biological Sciences, University of Southern California, Log Angeles, CA 90089., Gomez-Consarnau L; Department of Biological Sciences, University of Southern California, Log Angeles, CA 90089.; Departamento de Oceanografía Biológica, Centro de Investigación Científca y de Educación Superior de Ensenada, Ensenada, Baja California 22860, Mexico., Smith SN; Department of Earth, Marine, and Environmental Sciences, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599., Schofield O; Department of Marine and Coastal Sciences, Rutgers University, New Brunswick, NJ 08901., Yoshizawa S; Atmosphere and Ocean Research Institute, The University of Tokyo, Chiba 277-8564, Japan., Fujiwara T; Atmosphere and Ocean Research Institute, The University of Tokyo, Chiba 277-8564, Japan., Sunda WG; Department of Earth, Marine, and Environmental Sciences, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599., Hopkinson BM; Department of Marine Sciences, University of Georgia, Athens, GA 30602., Septer AN; Department of Earth, Marine, and Environmental Sciences, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599., Marchetti A; Department of Earth, Marine, and Environmental Sciences, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599. |
| Abstrakt: |
Photosynthetic carbon (C) fixation by phytoplankton in the Southern Ocean (SO) plays a critical role in regulating air-sea exchange of carbon dioxide and thus global climate. In the SO, photosynthesis (PS) is often constrained by low iron, low temperatures, and low but highly variable light intensities. Recently, proton-pumping rhodopsins (PPRs) were identified in marine phytoplankton, providing an alternate iron-free, light-driven source of cellular energy. These proteins pump protons across cellular membranes through light absorption by the chromophore retinal, and the resulting pH energy gradient can then be used for active membrane transport or for synthesis of adenosine triphosphate. Here, we show that PPR is pervasive in Antarctic phytoplankton, especially in iron-limited regions. In a model SO diatom, we found that it was localized to the vacuolar membrane, making the vacuole a putative alternative phototrophic organelle for light-driven production of cellular energy. Unlike photosynthetic C fixation, which decreases substantially at colder temperatures, the proton transport activity of PPR was unaffected by decreasing temperature. Cellular PPR levels in cultured SO diatoms increased with decreasing iron concentrations and energy production from PPR photochemistry could substantially augment that of PS, especially under high light intensities, where PS is often photoinhibited. PPR gene expression and high retinal concentrations in phytoplankton in SO waters support its widespread use in polar environments. PPRs are an important adaptation of SO phytoplankton to growth and survival in their cold, iron-limited, and variable light environment. |
