Evolution of pyrrolizidine alkaloids in Phalaenopsis orchids and other monocotyledons: Identification of deoxyhypusine synthase, homospermidine synthase and related pseudogenes

Phalaenopsis orchids produce pyrrolizidine alkaloids of the phalaenopsine type. Homospermidine synthase, the first specific enzyme of pyrrolizidine alkaloid biosynthesis, and the related deoxyhypusine synthase were identified together with several pseudogenes as remnants of ongoing gene duplication events in orchids.