Gene identification and functional characterization of a Δ12 fatty acid desaturase in Tetrahymena thermophila and its influence in homeoviscous adaptation to low temperature

• Published in: Biochimica et biophysica acta. Molecular and cell biology of lipids Vol. 1864; no. 11; pp. 1644 - 1655
• Main Authors: Sanchez Granel, Maria L., Cánepa, Camila, Cid, Nicolas G., Navarro, Juan C., Monroig, Óscar, Verstraeten, Sandra V., Nudel, Clara B., Nusblat, Alejandro D.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01-11-2019
• Subjects: Cold stress; Cold Temperature; Cold-Shock Response; Fatty acid desaturases; Fatty Acid Desaturases - genetics; Fatty Acid Desaturases - metabolism; Fatty Acids, Unsaturated - metabolism; Gene Knockdown Techniques; Homeoviscous adaptation; Membranes; Phospholipids - metabolism; Tetrahymena thermophila; Tetrahymena thermophila - enzymology; Tetrahymena thermophila - genetics; Tetrahymena thermophila - physiology; Triterpenes - metabolism; Δ12 fatty acid desaturase; ORF; Membranes; Homeoviscous adaptation; MUFA; Fatty acid desaturases; Δ12 fatty acid desaturase; MTT; OLE1; DES12; MSTFA; OLE2; SFA; Tetrahymena thermophila; 12-AS; WT; DES6B; DES6A; ΚΟΔ12; PUFA; FAD; 6-AS; FAME; PC; Cold stress; HGT; PE; TL; AEPL
• ISSN: 1388-1981; 1879-2618
• DOI: 10.1016/j.bbalip.2019.08.003

Homeoviscous adaptation in poikilotherms is based in the regulation of the level of desaturation of fatty acids, variation in phospholipids head groups and sterol content in the membrane lipids, in order to maintain the membrane fluidity in response to changes in environmental temperature. Increased proportion of unsaturated fatty acids is thought to be the main response to low-temperature acclimation, which is mostly achieved by fatty acid desaturases. Genome analysis of the ciliate Tetrahymena thermophila and a gene knockout approach has allowed us to identify one Δ12 FAD and to study its activity in the original host and in a yeast heterologous expression system. The “PUFA index” -relative content of polyunsaturated fatty acids compared to the sum of saturated and monounsaturated fatty acid content- was ~57% lower at 15 °C and 35 °C in the Δ12 FAD gene knockout strain (KOΔ12) compared to WT strain. We characterized the role of T. thermophila Δ12 FAD on homeoviscous adaptation and analyzed its involvement in cellular growth, cold stress response, and membrane fluidity, as well as its expression pattern during temperature shifts. Although these alterations allowed normal growth in the KOΔ12 strain at 30 °C or higher temperatures, growth was impaired at temperatures of 20 °C or lower, where homeoviscous adaptation is impaired. These results stress the importance of Δ12 FAD in the regulation of cold adaptation processes, as well as the suitability of T. thermophila as a valuable model to investigate the regulation of membrane lipids and evolutionary conservation and divergence of the underlying mechanisms.
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•A Δ12 FAD was identified and characterized from T. thermophila.•Gene knockout of Δ12 FAD decreased PUFA index by 60%.•Cell growth at low temperatures was impaired in the Δ12 FAD knockout strain.•Phospholipids and tetrahymanol content were altered in the Δ12 FAD knockout strain.•Δ12 FAD plays a critical role in the regulation of homeoviscous adaptation.