CBN-V Video Archives - S7-28
Down-regulation of CYP79D1 and CYP79D2 to Obtain Acyanogenic Cassava
(Manihot esculenta)

Siritunga D., R. Sayre

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

        Cassava leaves and roots contain potentially toxic levels of the cyanogenic glucoside, linamarin. Our objective has been to produce a safer cassava food product having reduced linamarin content. We report here the generation of transgenic cassava plants in which the expression of the genes encoding the cytochrome P450s (CYP79D1 and CYP79D2) that catalyze the first-dedicated step in linamarin synthesis have been inhibited. Using a leaf-specific Cab1 promoter to drive the antisense expression of the CYP79D1 and D2 genes we observed a complete loss of CYP79D1 and D2 transcripts in leaves. Analysis of the linamarin content of leaves from eight independent transformants with reduced CYP79D1 and D2 transcripts indicated that there was up to 80% reduction in leaf linamarin content. Currently, we are measuring the linamarin content of roots from these transgenic plants. In addition, we are measuring the linamarin content of leaves and roots from transgenic plants in which it is expected that CYP79D1 and D2 expression has been specifically suppressed in roots. These are the first cassava plants with greatly reduced cyanogenic glycosides in its leaves.

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