Effect of Temperature on the Desaturase Gene Translation in Spirulina Platensis Strain C1

Abstract

The cyanobacterium Spirulina platensis strain C 1 contains three desaturases, ∆⁹,∆¹² and ∆⁶. These desaturases introduce double bonds at the ∆⁹, ∆¹² and ∆⁶ position of fatty acids that have been esterified to glycerolipids. In cyanobacteria, the elevation of unsaturated fatty acid level in membrane lipids has been shown to play a major role in response to temperature change. We therefore carried out a study of the regulation of desaturase gene expression in response to temperature change in S. platensis strain C 1. In a previous study, it was found that the transcription of desC (∆⁹) and desA (∆ ¹²) was not affected by a temperature shift from 35 °C (normal growth temperature) to 22 °C or to 40 °C. However, while desC and desA remained unaffected, the transcription and mRNA stability of desD (∆⁶) were enhanced by lowering the temperature from 35 °C to 22 °C. In this study, these genes were studied at the translation level by Western blot analysis. Two synthetic peptides of ∆⁹ and ∆⁶ desaturases w1th 20 amino acids in length from the Cterminus were synthesized. Polyclonal antibodies, which were raised against these synthetic peptides, were used in the Western blot analysis. The level of ∆⁹ desaturase was not significantly affected in either thylakoid or plasma membrane after the temperature shift. By contrast, it was found that ∆⁶ desaturase increased in thylakoid membrane after lowering the temperature from 35 °C to 22 ^°C for 24 h, although it remained constant in plasma membrane. These results indicate that the expression of the ∆⁶desaturase gene is up regulated by temperature in different ways in two types of lipid membranes, while that of ∆⁹desatura.se is temperature independent.