Spirulina Platensis Mutants Defective in γ-Linolenic Acid Production: Molecular characterization

Abstract

Spirulina platensis, a filamentous cyanobacteria, has been a potential alternative source for a production of γ-linolenic acid (GLA, 18:3Δ6,9,12). This essential polyunsaturated fatty acid (PUFA) is of profound interest as its pharmaceutical values (see reviews in 1). Recently, Spirulina is commercially cultivated in several countries, mainly as a health food and feed, therefore choice of strains are required. In our laboratory, attempt to improve and select a high GLA producing strain(s) with high economic value, chemical treatment using SAN9785 (BASF 13–338, 4-chloro-5(dimethylamino)-2-phenyl-3(2H) pyridazinone) (2) or ethyl-methanesulfonate (EMS) have been investigated. However, we have obtained four mutants defective in the GLA production, namely I18, 122, 130 and 130/1, during a strain selection after EMS-mutagenesis. Reduction in the GLA level to half of that of wild type was found in the first three strains, but not in the 130/1 which completely lacked of the GLA. These mutants might be used as an alternative tools for clearly understand in the biosynthesis of the GLA. Since acyl-lipid desaturases are the enzymes that introduce double bond into fatty acids that are bound to glycerolipids in cyanobacteria (3). In this report, we thus examined the molecular characterization of desD, gene coding for Δ6-acyl lipid-desaturase, of the mutants in comparative to that of the wild type (WT), including the transcription level.