Differences in the control of the temperature-dependent expression of four genes for desaturases in Synechocystis sp. PCC 6803.

Cyanobacteria are capable of desaturating the fatty acids in their membrane lipids in response to decreases in temperature. The cyanobacterium, Synechocystis sp. PCC 6803, contains four desaturases, which specifically catalyse desaturation at the delta6, delta9, delta12 and omega3 positions of fatty acids. The levels of the mRNAs transcribed from the genes that encode the delta6, delta12 and omega3 desaturases increased about 10-fold, but at different rates, upon a decrease in temperature from 34 degrees C to 22 degrees C, whereas the level of the mRNA for the delta9 desaturase remained constant. The increases in the levels of mRNAs were caused both by the enhanced transcription and by the increased stability of the mRNAs at the low temperature. Western blotting analysis demonstrated that levels of the delta6, delta12 and omega3 desaturases increased at different rates at the low temperature, while that of the delta9 desaturase remained constant. These observations indicate that the expression of the genes for the four desaturases is regulated by temperature in different ways.