Collectively plants synthesize a diverse array of “Plant Natural Products” (PNPs) either as part of normal growth and development or in response to stress. PNPs represent a vast resource of complex molecules that are exploited by man for their pharmacological and other properties. Fenugreek (Trigonella foenum-graecum L.) is an unexploited leguminous plant with a rich PNP repertoire including terpenoids and flavonoids.

Isoflavonoid pterocarpans, like medicarpin (M), are produced by leguminous plants in response to biotic or abiotic elicitation. Previously, we have investigated the biosynthesis and involvement of the phytoalexin Medicarpin (M) in a general metal and metalloid detoxification mechanism. Our data showed that, depending on copper concentrations, M was formed either de novo or at the expense of its malonyl glucoside. The increased PAL activity as well as the accumulation of CHS and VR specific transcripts are consistent with the de novo synthesis of M upon elicitation with low copper concentrations. Furthermore, elicitation of seedlings with three metals (copper, cadmium and aluminum) and one metalloid (selenium) significantly induced an increase in the expression of M biosynthetic genes and a concomitant increase of M and citrate exudation in the culture medium. Taken together, along with the moderate effects of the elicitors on root growth and the plasma membrane integrity, our results indicate that M and citrate exudation may participate, as part of a non-element-specific resistance mechanism, in metal and Se detoxification.

Very little is known about the enzymes and genes involved in the biosynthesis of terpenoids and flavonoids in Fenugreek. It would be a huge advantage if the biosynthesis of complex PNPs could be enhanced, or even modified, in order to provide unlimited resources for valuable drugs and fine chemicals. We are currently pursuing the cloning of several key genes involved in these biosynthetic pathways. Outcomes will help us in pathway engineering and in the design of plants as possible production platforms of important PNPs.