Rj. Grebenok et al., CHARACTERIZATION OF ZEA-MAYS ENDOSPERM C-24 STEROL METHYLTRANSFERASE - ONE OF 2 TYPES OF STEROL METHYLTRANSFERASE IN HIGHER-PLANTS, Plant molecular biology, 34(6), 1997, pp. 891-896
We report the characterization of a higher-plant C-24 sterol methyltra
nsferase by yeast complementation. A Zea mays endosperm expressed sequ
ence tag (EST) was identified which, upon complete sequencing, showed
46% identity to the yeast C-24 methyltransferase gene (ERG6) and 75% a
nd 37% amino acid identity to recently isolated higher-plant sterol me
thyltransferases from soybean and Arabidopsis, respectively. When plac
ed under GAL4 regulation, the Z. mays cDNA functionally complemented t
he erg6 mutation, restoring ergosterol production and conferring resis
tance to cycloheximide. Complementation was both plasmid-dependent and
galactose-inducible. The Z. mays cDNA clone contains an open reading
frame encoding a 40 kDa protein containing motifs common to a large nu
mber of S-adenosyl-L-methionine methyltransferases (SMTs). Sequence co
mparisons and functional studies of the maize, soybean and Arabidopsis
cDNAs indicates two types of C-24 SMTs exist in higher plants.