Cold-Induced Expression of Δ ⁹ -Desaturase in Carp by Transcriptional and Posttranslational Mechanisms

Abstract

Poikilothermic animals respond to chronic cold by increasing phosphoglyceride unsaturation to restore the fluidity of cold-rigidified membranes. Despite the importance of this compensatory response, the enzymes involved have not been clearly identified, and the mechanisms that control their activity are unknown. In carp liver, cold induces an 8- to 10-fold increase in specific activity of the microsomal stearoyl coenzyme A desaturase. Cold-induced up-regulation of gene transcription resulted in a 10-fold increase in desaturase transcript amounts after 48 to 60 hours. However, this increase was preceded by the activation of latent desaturase, probably by a posttranslational mechanism. These two mechanisms may act sequentially to match desaturase expression to the demands imposed by a progressive decrease in temperature.

Environmental and dietary influences on highly unsaturated fatty acid biosynthesis and expression of fatty acyl desaturase and elongase genes in liver of Atlantic salmon (Salmo salar)

“…However, regulation of other fatty acid desaturase genes by environmental factors is well established, specifically in relation to homeoviscous adaptation. The expression of stearoyl-CoA (Δ9) desaturase, responsible for the conversion of 18:0 to 18:1n-9, has been shown to be cold-induced in carp (Cyprinus carpio) [44]. Subsequently, it was demonstrated that there were two Δ9 isoforms in carp, Cds1 and Cds2, which showed differential expression in response to diet (induced by high saturated fat) and temperature, respectively [45].…”

Metabolism and Functions of Lipids and Fatty Acids in Teleost Fish

“…The stearoyl Δ9 fatty acid desaturase (SCD) activity has been particularly well characterised and its gene cloned in several animal species including common carp and grass carp (Chang et al, 2001). Tiku et al (1996) screened a carp hepatic cDNA library with a rat Δ9 SCD probe yielding several putative positive clones which were tested against cold-induced carp liver RNA samples using Northern blot analysis, and a 2.7 kb transcript was detected. One of the clones had an open reading frame which encoded a 292 residue polypeptide with calculated molecular weight of 33.6 kDa.…”

How insects survive the cold: molecular mechanisms—a review

“…The enzyme ∆9-acyl-CoA desaturase plays an essential role in HVA by increasing the ratio of unsaturated to saturated fatty acids in cell membranes and is expressed at low temperatures in fish (Tiku et al 1996), bacteria (Sakamoto and Bryant, 1997) …”