AUTHOR=Raymond James A. , Morgan-Kiss Rachael , Stahl-Rommel Sarah 

TITLE=Glycerol Is an Osmoprotectant in Two Antarctic Chlamydomonas Species From an Ice-Covered Saline Lake and Is Synthesized by an Unusual Bidomain Enzyme

JOURNAL=Frontiers in Plant Science

VOLUME=11

YEAR=2020

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2020.01259

DOI=10.3389/fpls.2020.01259

ISSN=1664-462X

ABSTRACT=<p>Glycerol, a compatible solute, has previously been found to act as an osmoprotectant in some marine <italic>Chlamydomonas</italic> species and several species of <italic>Dunaliella</italic> from hypersaline ponds. Recently, <italic>Chlamydomonas reinhardtii</italic> and <italic>Dunaliella salina</italic> were shown to make glycerol with an unusual bidomain enzyme, which appears to be unique to algae, that contains a phosphoserine phosphatase and glycerol-3-phosphate dehydrogenase. Here we report that two psychrophilic species of <italic>Chlamydomonas</italic> (<italic>C</italic>. spp. UWO241 and ICE-MDV) from Lake Bonney, Antarctica also produce high levels of glycerol to survive in the lake’s saline waters. Glycerol concentration increased linearly with salinity and at 1.3 M NaCl, exceeded 400 mM in <italic>C</italic>. sp. UWO241, the more salt-tolerant strain. We also show that both species expressed several isoforms of the bidomain enzyme. An analysis of one of the isoforms of <italic>C</italic>. sp. UWO241 showed that it was strongly upregulated by NaCl and is thus the likely source of glycerol. These results reveal another adaptation of the Lake Bonney <italic>Chlamydomonas</italic> species that allow them to survive in an extreme polar environment.</p>