Photo-acclimation of the psychrophilic Chlamydomonas raudensis to light quality mimics adaptation to the Antarctic winter
Rachael M. Morgan-Kiss1, Michael Lizotte2, Weidong Kong1, and John C. Priscu3
1) Department of Microbiology, Miami University, Oxford, OH
2) Oshkosh Aquatic Research Laboratory, University of Wisconsin Oshkosh, Oshkosh, WI
3) Department of Land Resources and Environmental Sciences, Montana State University, MT
Photosynthetic microorganisms that reside in the polar regions of the world have a unique problem to contend with in that their energy source is completely absent for 4 to 6 months during the polar winter. The psychrophilic green alga, Chlamydomonas raudensis UWO241, was isolated from the ice-covered Lake Bonney (located in the McMurdo Dry Valleys, Antarctica) and represents one of the best algal models for adaptation of photosynthetic processes to permanent low temperatures. Over a decade of work on this "photopsychrophile" has characterized how the photosynthetic apparatus of this enigmatic green alga is fine-tuned to efficiently harvest and transduce light energy of low fluency and enriched in blue-green wavelengths. However, as a consequence of photoadaptation to permanent shade, C. raudensis has lost a number of photo-acclimatory responses to environmental variability as well as the ability to grow in a light regime enriched in long (red) wavelengths. Here we report a novel in situ incubation study to validate our hypothesis that responses to red light in laboratory cultures mimic winter adaptation in C. raudensis. Our study represents the first to examine how a dry valley lake phytoplankton species residing in the deepest photic zone in the water column adapts to the transition from summer to complete winter darkness. This work was supported by the National Science Foundation Office of Polar Programs (OPP-0631659).
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