Abstract
Oxidative stress is a particularly severe threat to Antarctic marine polar organisms because they are exposed to high dissolved oxygen and to intense UV radiation. This paper reports the features of three superoxide dismutases from the Antarctic psychrophilic ciliate Euplotes focardii that faces two environmental challenges, oxidative stress and low temperature. Two out of these are Cu,Zn superoxide dismutases (named Ef-SOD1a and Ef-SOD1b) and one belongs to the Mn-containing group (Ef-SOD2). Ef-SOD1s and Ef-SOD2 differ in their evolutionary history, expression and overall structural features. Ef-SOD1 genes are expressed at different levels, with Ef-SOD1b mRNA 20-fold higher at the ciliate optimal temperature of growth (4 °C). All Ef-SOD enzymes are active at 4 °C, consistent with the definition of cold-adapted enzymes. At the same time, they display temperatures of melting in the range 50–70 °C and retain residual activity after incubation at 65–75 °C. Supported by data of molecular dynamics simulation, we conclude that the E. focardii SODs combine cold activity, local molecular flexibility and thermo tolerance.
Highlights
Polar marine organisms face a number of environmental challenges, in particular the adverse effects of cold on key biological processes and high oxidative stress[1,2]
Putative Cu,Zn SOD coding sequences identified by BLAST search in the E. focardii transcriptome were reported in a previous work and named Ef-SOD1a and Ef-SOD1b29
The topology of the tree suggests that SOD1 evolutionary history would have witnessed multiple events of gene duplication followed by sequence diversification even inside homogeneous groups of ciliate and bacteria, whereas SOD2 sequences are more conserved
Summary
Polar marine organisms face a number of environmental challenges, in particular the adverse effects of cold on key biological processes and high oxidative stress[1,2]. “psychrophilic” organisms rely on adaptive changes, that include the up-regulation of genes encoding proteins involved in metabolite transport, the synthesis of cryoprotectors (mannitol, polyamines), increased membrane fluidity and the production of enzymes endowed with high activity at low temperature[4]. MnSOD and FeSOD can be either homodimers or homotetramers and share high similarity in sequence and structure[22,23,24], strongly suggesting a common evolutionary origin. We show that the two SOD families likely followed different evolutionary history They share similar temperature-dependent regulation of expression and combine cold activity with thermo-tolerance, a feature that could have played a role in the successful colonization of the Antarctic marine habitat by this ciliate
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
