Construction and functional analysis of fatty acid desaturase gene disruptants in Candida albicans

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Abstract
Polyunsaturated fatty acids (PUFAs), including linoleic acid (C18 : 2) and α-linolenic acid (C18 : 3), are major components of membranes. PUFAs are produced from monounsaturated fatty acids by several fatty acid desaturases (FADs) in many fungi, but Saccharomyces cerevisiae, Schizosaccharomyces pombe and humans do not have these enzymes. Although the fungal pathogen Candida albicans produces C18 : 2 and C18 : 3, the enzymes that synthesize them have not yet been investigated. In this report, two ORFs, CaFAD2 and CaFAD3, were identified based on their homology to other yeast FADs, and CaFAD2 and CaFAD3 gene disruptants were constructed. Cafad2Δ and Cafad3Δ lost their ability to produce C18 : 2 and C18 : 3, respectively. Furthermore, S. cerevisiae cells expressing CaFad2p converted palmitoleic acid (C16 : 1) and C18 : 1 to hexadecadienoic acid (C16 : 2) and C18 : 2, respectively, and CaFad3p-expressing cells converted C18 : 2 to C18 : 3. These results strongly supported that CaFAD2 encodes the Δ12 FAD and that CaFAD3 encodes the ω3 FAD. However, phenotypic analysis demonstrated that the presence of these PUFAs did not affect the virulence to mice, or morphogenesis in the culture media used to induce morphological change of C. albicans.