The invention relates generally to phosphopantetheinyl transferases that are required for activation of a polyketide synthase complex to synthesize long chain poly-unsaturated fatty acids (LC-PUFA's) such as docosahexaenoic acid and eicosapentaenoic acid. In particular, the invention relates to bacterial phosphopantetheinyl transferases, DNA constructs for their expression in host cells, and seed, oil and meal when the host cells comprise a plant. Also provided is a method for making a plant oil containing docosahexaenoic acid and/or eicosapentaenoic acid.