Isolation of cycloeucalenol cycloisomerase (CYC1) by expressed sequence tag mining in fenugreek (Trigonella foenum-graecum)

Fenugreek (Trigonella foenum-graecum L.) has a long and respected history of medicinal uses in Middle Eastern and Persian medicine. The hypocholesterolemic and hypoglycemic effects of fenugreek were attributed to its major steroidal sapogenin, diosgenin. The knowledge of the diosgenin biosynthesis pathway is derived from studies of sitosterol production through acetyl-CoA. Cycloeucalenol cycloisomerase (CYC1) plays an important role in the biosynthesis of diosgenin. This enzyme is involved in the synthesis of plant sterols, by converting pentacyclic cyclopropyl (cycloeucalenol) sterols to tetracyclic sterols (obtusifoliol). A full-length cDNA encoding CYC1 was isolated from young leaves of T. foenum-graecum by reverse transcription-PCR. The full-length cDNA of CYC1 was found to have a 924 bp open reading frame, encoding a protein with 307 amino acid residues. The deduced amino acid sequence of CYC1 showed the highest identity (97%) Medicago sativa cycloeucalenol cycloisomerase. This study provides an important resource for the scientific community, interested in the molecular genetics and functional genomics of fenugreek.