Transformation of Saccharomyces cerevisiae with a cDNA encoding a sterol C‐methyltransferase from Arabidopsis thaliana results in the synthesis of 24‐ethyl sterols

Abstract

Using an EST‐cDNA probe, a full‐length cDNA (411) sequence of 1411 bp was isolated from A. thaliana. This sequence contained features typical of methyltransferases in general and in particular showed 38% identity with ERG6, a S. cerevisiae gene which encodes the zymosterol‐C‐24‐methyltransferase. A yeast vector containing this ORF (4118‐pYeDP60) was used to transform a wild type S. cerevisiae which accumulates predominantly ergosterol, a 24‐methyl sterol as well as a mutant erg6 null mutant accumulating principally zymosterol, a sterol non‐alkylated at C‐24. In both cases, several 24‐ethyl‐ and 24‐ethylidene sterols were synthetized indicating that the 4118 cDNA encodes a plant sterol C‐methyltransferase able to perform two sequential methylations of the sterol side chain.