The present invention relates to a method for the production of fatty acid
esters which comprise unsaturated fatty acids with at least three double
bonds, and to free unsaturated fatty acids with a content of at least 1%
by weight based on the total fatty acids present in the plants, by
expressing at least one nucleic acid sequence which encodes a polypeptide
with .DELTA.6-desaturase activity and at least one nucleic acid sequence
which encodes a polypeptide with .DELTA.6-elongase activity.
Advantageously, these nucleic acid sequences can, if appropriate, be
expressed in the transgenic plant together with a third nucleic acid
sequence which encodes a polypeptide with .DELTA.5-desaturase activity.
The invention furthermore relates to the use of defined nucleic acid
sequences which encode polypeptides with a .DELTA.6-desaturase activity,
.DELTA.6-elongase activity or .DELTA.5-desaturase activity selected from
a group of nucleic acid sequences, and/or to the use of nucleic acid
constructs comprising the abovementioned nucleic acid sequences.