Original Article

Metabolomics

, Volume 3, Issue 3, pp 383-398

Lessons learned from metabolic engineering of cyanogenic glucosides

  • Anne Vinther MorantAffiliated withPlant Biochemistry Laboratory, Department of Plant Biology, Center for Molecular Plant Physiology (PlaCe)
  • , Kirsten JørgensenAffiliated withPlant Biochemistry Laboratory, Department of Plant Biology, Center for Molecular Plant Physiology (PlaCe)
  • , Bodil JørgensenAffiliated withCell Wall Biology and Molecular Virology, Center for Molecular Plant Physiology (PlaCe)
  • , Winnie DamAffiliated withCell Wall Biology and Molecular Virology, Center for Molecular Plant Physiology (PlaCe)Aresa A/S
  • , Carl Erik OlsenAffiliated withDepartment of Natural Sciences, Center for Molecular Plant Physiology (PlaCe)
  • , Birger Lindberg MøllerAffiliated withPlant Biochemistry Laboratory, Department of Plant Biology, Center for Molecular Plant Physiology (PlaCe)
  • , Søren BakAffiliated withPlant Biochemistry Laboratory, Department of Plant Biology, Center for Molecular Plant Physiology (PlaCe) Email author 

Abstract

Plants produce a plethora of secondary metabolites which constitute a wealth of potential pharmaceuticals, pro-vitamins, flavours, fragrances, colorants and toxins as well as a source of natural pesticides. Many of these valuable compounds are only synthesized in exotic plant species or in concentrations too low to facilitate commercialization. In some cases their presence constitutes a health hazard and renders the crops unsuitable for consumption. Metabolic engineering is a powerful tool to alter and ameliorate the secondary metabolite composition of crop plants and gain new desired traits. The interplay of a multitude of biosynthetic pathways and the possibility of metabolic cross-talk combined with an incomplete understanding of the regulation of these pathways, explain why metabolic engineering of plant secondary metabolism is still in its infancy and subject to much trial and error. Cyanogenic glucosides are ancient defense compounds that release toxic HCN upon tissue disruption caused e.g. by chewing insects. The committed steps of the cyanogenic glucoside biosynthetic pathway are encoded by three genes. This unique genetic simplicity and the availability of the corresponding cDNAs have given cyanogenic glucosides pioneering status in metabolic engineering of plant secondary metabolism. In this review, lessons learned from metabolic engineering of cyanogenic glucosides in Arabidopsis thaliana (thale cress), Nicotiana tabacum cv Xanthi (tobacco), Manihot esculenta Crantz (cassava) and Lotus japonicus (bird’s foot trefoil) are presented. The importance of metabolic channelling of toxic intermediates as mediated by metabolon formation in avoiding unintended metabolic cross-talk and unwanted pleiotropic effects is emphasized. Likewise, the potential of metabolic engineering of plant secondary metabolism as a tool to elucidate, for example, the impact of secondary metabolites on plant–insect interactions is demonstrated.

Keywords

Cyanogenic glucosides Metabolic engineering RNAi Transgene silencing 5′-Azacytidine