CBN-V Video Archives - S7-27
Reduction in the Cyanogenic Potential of Cassava Roots; Transgenic Plants Expressing Hydroxynitrile Lyase in the Roots

Siritunga D., D. Arias-Garcon and R. Sayre

Dept. of Plant Biology, Ohio State University, Columbus, OH 43210 siritunga.1@osu.edu

        Unlike leaves, cassava roots lack the enzyme hydroxynitrile lyase (HNL) which converts acetone cyanohydrin (from linamarin de-glycosylation) into cyanide plus acetone. As a result poorly processed cassava plants may contain sufficient quantities of acetone cyanohydrin to cause cyanide associated disorders in consumers. We report here the stable genetic transformation of cassava with a cassava HNL gene whose expression is regulated by the 2x35S constitutive promoter. Hydroxynitrile lyase activity from leaves and stems of transformed plants was up to 2.3 fold higher than wild type. Higher HNL levels were associated with a 61% decrease in total acetone cyanohydrin in roots following processing for 120 minutes. Cassava transformants expressing HNL in roots are expected to accelerate the cyanogen detoxification process and in turn provide a safer food product for human consumption. Significantly, these plants will maintain normal levels of cyanogenic glycosides prior to cell rupture, thus providing the same herbivore deterrent capabilities as wild type.

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