Functional identification of sterol-4 alpha-methyl oxidase cDNAs from Arabidopsis thaliana by complementation of a yeast erg25 mutant lacking sterol-4 alpha-methyl oxidation

Specific primers derived from both genomic sequence data and EST cDNA seque nces were used to polymerase chain reaction amplify two full-length cDNA se quences AtSMO1 and AtSMO2), 801 and 783 bp, respectively, from an Arabidops is thaliana cDNA library. The predicted proteins show 32 and 29% identity t o the ERG25 gene from Saccharomyces cerevisiae which encodes the sterol-4 a lpha -methyl oxidase (SMO), a membrane-bound non-heme di-iron oxygenase inv olved in lipid metabolism. Heterologous expression of AtSMO1 and AtSMO2 in a yeast erg25 ergosterol auxotroph, lacking SMO activity, restored growth a nd endogenous ergosterol synthesis. These results represent the first funct ional identification of SMO genes from plants. (C) 2001 Federation of Europ ean Biochemical Societies. Published by Elsevier Science B.V. All rights re served.