Crop defence response on-demand

The METDEF (Metabolic engineering of triterpenoid pathways involved in plant defence in Arabidopsis and rice) project has developed a toolkit containing genes and enzymes for construction of triterpenoid glycosides in some cereals. Rice and maize for example do not naturally produce triterpenoids.

Using the 'Golden Gate Assembly' technique for multi-gene vector assembly and cloning, the resulting toolkit was validated in Nicotiana benthamiana, a close relative to tobacco.

The researchers then worked on transforming the model plant Arabidopsis and successfully obtained compounds from the avenacin metabolic pathway, an anti-fungal growth compound found naturally in oat roots. Furthermore, the scientists transformed another triterpenoid amyrin, a constituent of dandelion coffee.

Following another arm of synthetic biology, the researchers worked on making clusters of genes that confer designer traits in crop plants. These would then be controlled by environmental cues so the genes were only expressed when necessary. For example, nutrient production when food is limited.

Using a substance present in sorghum, dhurrin, that repels insects, the researchers made different clusters containing three dhurrin genes under the control of varying promoters. Different lines contained dhurrin, a result with great significance as responses to developmental, environmental and chemical cues can be constructed.

Applications for the METDEF biotechnology are spread widely across agricultural production to enhance food security. Tailoring engineered plants to express inserted genes could include not only pathogens but response to circadian clock, lack of oxygen and low nutrient levels.