Evidence for phenotypic plasticity in the Antarctic extremophile Chlamydomonas raudensis Ettl. UWO 241

Abstract

Life in extreme environments poses unique challenges to photosynthetic organisms. The ability for an extremophilic green alga and its genetic and mesophilic equivalent to acclimate to changes in their environment was examined to determine the extent of their phenotypic plasticities. The Antarctic extremophile Chlamydomonas raudensis Ettl. UWO 241 (UWO) was isolated from an ice-covered lake in Antarctica, whereas its mesophilic counterpart C. raudensis Ettl. SAG 49.72 (SAG) was isolated from a meadow pool in the Czech Republic. The effects of changes in temperature and salinity on growth, morphology, and photochemistry were examined in the two strains. Differential acclimative responses were observed in UWO which include a wider salinity range for growth, and broader temperature- and salt-induced fluctuations in Fv/Fm, relative to SAG. Furthermore, the redox state of the photosynthetic electron transport chain, measured as 1–qP, was modulated in the extremophile whereas this was not observed in the mesophile. Interestingly, it is shown for the first time that SAG is similar to UWO in that it is unable to undergo state transitions. The different natural histories of these two strains exert different evolutionary pressures and, consequently, different abilities for acclimation, an important component of phenotypic plasticity. In contrast to SAG, UWO relied on a redox sensing and signalling system under the growth conditions used in this study. It is proposed that growth and adaptation of UWO under a stressful and extreme environment poises this extremophile for better success under changing environmental conditions.

Temperature dependence of photosynthesis and thylakoid lipid composition in the red snow algaChlamydomonascf.nivalis(Chlorophyceae)

“…Snow algae from the genera Chloromonas and Chlamydomonas were considered to be obligate cryophiles with optimal growth below 10 °C (Hoham, ). Low temperature growth optima were reported, for example for Chloromonas pichinchae (1 °C; Hoham, ), Chloromonas chenangoensis , Chloromonas tughillensis (2.5–5 °C; Hoham et al ., ), C. raudensis (8 °C; Pocock et al ., ) and Chlamydomonas sp. (5 °C; Eddie et al ., ).…”

Separate Origins of Ice-Binding Proteins in Antarctic Chlamydomonas Species

“…To characterize the IBPs of a second chlamydomonad alga, we selected C. raudensis UWO241, a species that was isolated from a permanently ice-covered Antarctic lake [5], [6] and that has been the subject of many studies on the adaptation to extreme conditions, including low light [7], low temperature [8] and high salinity [9]. We obtained the IBP sequences of C. raudensis UWO241 by sequencing the transcriptome, confirmed that they encode IBPs, and compared the ice-binding activities of C. raudensis UWO241 and a mesophilic sister species.…”

Growth response of Antarctic snow microalgae cultures belonging to the Chlamydomonadaceae family to effects of temperature, irradiance and supporting media

“…Despite their diversity, snow algae share their main property: Their optimum growth temperatures are generally around 0 o C (Teoh et al 2004). To adapt to this harsh environment, they developed a number of adaptive features, which include biosynthesis of pigments (Fong et al 2001), polyols (Arnold et al 2003, Leya et al 2009), sugars (Arnold et al 2003, lipids, and spore formation (Pocock et al 2011, Zang et al 2003. The spores, which withstand subzero temperatures in winter, usually have large amounts of lipid reserves, polyols and sugars (Rezanka et al 2008).…”