|Novy, Richard - Rich|
|Belknap, William - Bill|
Submitted to: Acta Horticulturae
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/8/2006
Publication Date: 7/17/2007
Citation: Mc Cue, K.F., Allen, P.V., Shepherd, L.V., Blake, A., Rockhold, D.R., Novy, R.G., Stewart, D., Davies, H.V., Belknap, W.R. 2007. Manipulation and compensation of steroidal glycoalkaloid biosynthesis in potatoes. Acta Horticulturae. 745: 343-349. Interpretive Summary: Potatoes produce bitter compounds called steroidal glycoalkaloids (SGAs). SGAs are also found in the potato relatives tomato and eggplant. High levels of SGAs are undesirable. When potatoes are exposed to light they turn green and start to accumulate SGAs. High levels can also be caused by bruising, adverse environmental conditions during growth, and during breeding of potatoes for new varieties. As part of a program to improve potatoes with biotechnology we are using natural potato genes that attach sugar molecules to the SGAs. By introducing the genes backwards, we can stop the sugar addition and prevent the accumulation of SGAs. By introduction of genes we have significantly altered the accumulation of SGAs. This research is carried out in the Crop Improvement and Utilization Research Unit in cooperation with the Small Grains and Potato Germplasm Research Unit and the Scottish Crop Research Institute. The results have confirmed the identity of new genes in the pathway and this information will be used to isolate and identify other SGT genes that can be used in future efforts to reduce accumulation of all SGAs top benefit potato breeders, producers and consumers.
Technical Abstract: Steroidal glycoalkaloids (SGAs) are undesirable secondary metabolites produced in Solanaceous plants including, potato, tomato and eggplant. Two tri-glycosylated alkaloids, alpha-chaconine and alpha-solanine occur naturally in potato tubers and can accumulate to excessive levels due to mechanical, environmental and genetic perturbations. We have identified members ot the SGA glycosyl transferasese gene family coding the UDP-galactose:solanidine galactosyltransferase (Sgt1), the UDP-glucose:solanidine glucosyltransferase (Sgt2), and the UDP-rhamnose:beta-solanine/ beta-chaconine rhamnosyltransferase (Sgt3). Reverse genetic manipulation of the Sgt gene family members using transgenic lines expressing acitve antisense gene constructs results in a shift of SGA pathway flux resulting in compensation by other pathway intermediates and products. New Sgt gene family members are being studied to verify the substrate specificity and biosynthetic sequence. Additional studies are underway to use the members of this gene family to completely block accumulation of SGAs in tubers.