Eliminating Cyanoglucosides from Cassava Tubers: Exploiting the Endogenous Turnover and Transporters

Cassava (Manihot esculenta Crantz) is a major staple food in sub-Saharan Africa. Its efficient utilization for food is affected by the presence of cyanoglucosides in the tubers. Following the mapping of CYP79D1/D2 genes involved in the cyanoglucosides biosynthesis, the last two decades have witnessed intense research to develop cassava plants with insignificant level of cyanoglucosides via gene silencing. These concerted efforts are yet to produce satisfactory outcomes. However, research has revealed roles of cyanoglucosides in important metabolic pathways in cassava. Therefore, an alternative direction must be sought to conserve the functions of these metabolites while eliminating the compounds from the edible tubers. The endogenous turnover and transport pathways of cyanoglucosides could be interesting areas for future research. It is expected that the upregulation of the genes involved in the turnover pathway would result in increased synthesis of these turnover products, which would subsequently be incorporated into primary metabolism; thereby avoiding the accumulation of cyanoglucosides in the tubers. Similarly, the characterization of glucosinolate transporters in Arabidopsis presents an avenue to study the mechanisms and roles of transporters of defense compounds such as cyanoglucosides in cassava. Research has shown that the metabolic engineering of these compounds are possible by interfering with the expression of transport molecules, and holds the potential for developing plants with reduced accumulation of toxic compounds in the edible tissues or plant parts. The objective of this study was to document recent literature and highlight pathways that involve turning cyanoglucosides into useful intermediates which could be exploited in developing cyanoglucosides-free cassava tubers.