Gene identification and functional characterization of a 12 fatty acid desaturase in Tetrahymena thermophila and its influence in homeoviscous adaptation to low temperature

MARIA LUZ SANCHEZ; CANEPA CAMILA; CID NICOLAS; JUAN NAVARRO; ÓSCAR MONROIG; VERSTRAETEN SANDRA; B.C. NUDEL; A. D. NUSBLAT

BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR AND CELL BIOLOGY OF LIPIDS

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2019

1388-1981

Homeoviscous adaptation in poikilotherms is based inthe regulation of the level of desaturation of fatty acids, variation inphospholipids head groups and sterol content in the membrane lipids, in orderto maintain the membrane fluidity in response to changes in environmentaltemperature. Increased proportion of unsaturated fatty acids is thought to bethe main response to low-temperature acclimation, which is mostly achieved byfatty acid desaturases. Genome analysis of the ciliate Tetrahymena thermophila and a gene knockout approach has allowed usto identify one D12 FAD and to study its activity in the original hostand in a yeast heterologous expression system. The ?PUFA index? -relative content of polyunsaturatedfatty acids compared to the sum of saturated and monounsaturated fatty acidcontent- was ~57% lower at 15°C and 35°C in the D12FAD gene knockout strain(KOΔ12) comparedto WT strain. We characterizedthe role of T. thermophila D12FAD on homeoviscous adaptation and analyzed its involvement in cellular growth, cold stress response, and membranefluidity, as well as its expression pattern during temperature shifts. Although these alterations allowed normal growth inthe KOΔ12 strain at 30°C or higher temperatures, growth wasimpaired at temperatures of 20°C or lower, where homeoviscous adaptation isimpaired. These results stress the importance of Δ12 FADin the regulation of coldadaptation processes, as wellas the suitability of T. thermophilaas a valuable model to investigate the regulation of membrane lipids andevolutionary conservation and divergence of the underlying mechanisms.