Production of prostaglandins in transgenic Arabidopsis thaliana

Plants do not naturally produce the very-long-chain polyunsaturated fatty acids that are the precursors of prostaglandins, but in previous studies Arabidopsis thaliana had been transformed sequentially with genes encoding a Δ(9)-elongase and a Δ(8)-desaturase to produce dihomo-γ-linolenic acid (DGLA) and eicosatetraenoic acid (ETA), and subsequently with a gene encoding a Δ(5)-desaturase to produce arachidonic acid (AA) and eicosapentaenoic acid (EPA). Transformation of A. thaliana with the first two genes consolidated on a single binary vector yielded transformants producing high levels of DGLA, and these plants were further transformed with mouse prostaglandin H synthase (PGH) genes to produce prostaglandins. Mouse PGHS-1 and PGHS-2 cDNAs were amplified for expression as three isoforms: PGHS-1 (complete coding sequence with signal peptide), PGHS-1-Ma (mature PGHS-1 sequence, without signal peptide) and PGHS-2 (complete coding sequence with signal peptide). PGHS-1 transformants showed the highest activity, followed by PGHS-2 transformants, whereas removal of the signal peptide resulted in almost complete loss of PGHS-1 activity. In order to produce a physiologically active prostaglandin, the Trypanosoma brucei prostaglandin F synthase gene was combined with the mouse PGHS-1 gene and the Mortierella alpina Δ(5)-desaturase on a binary vector. Transformation of DGLA-producing A. thaliana with this construct yielded transformants that successfully produced prostaglandin F.