|Belknap, William - Bill|
Submitted to: Acta Horticulturae
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/27/2003
Publication Date: 1/26/2004
Citation: Mc Cue, K.F., Corsini, D.L., Allen, P.V., Rockhold, D.R., Mccree, M.M., Sheperd, L., Moehs, C.P., Joyce, P., Davies, H.V., Belknap, W.R. 2004. Reduction of total steroidal glycoalkaloids in potato tubers using antisense constructs of a gene encoding a solanidine glucosyl transferase. Acta Horticulturae. 619: 77-86 (2003) Interpretive Summary: Steroidal glycoalkaloids (SGA) are undesirable metabolites found in potatoes and other Solanaceous commodities including the tomato. SGA accumulation affects food quality and safety and guidelines establish limits in commercial potato cultivars. High levels of SGAs hamper breeding efforts to develop new and improved varieties of potatoes. Part of our program to improve potato cultivars using molecular genetics is to reduce SGAs to assist breeding efforts and ensure food safety. We are using the solanidine glucosyltransferase (SGT) gene isolated from cultivated potatoes that is involved in SGA biosynthesis to turn of biosynthesis in potato tubers. Transgenic lines of potato containing the SGT transgenes exhibit phenotypes with significantly lower SGAs. Field trails over several years in Idaho and Wisconsin resulted in reproducible and statistically significant reductions of up to 40% of tuber SGAs in the cultivar Lenape. Analysis of transgenic lines of cultivar Desiree revealed essentially complete elimination of one of the two major SGAs in potato tubers. The second major SGA in tubers of these lines was not significantly affected. Additional genes encoding SGT and other SGA related sequences are currently being evaluated for introduction into new potato cultivars for improved agronomic and quality properties.
Technical Abstract: Accumulation of steroidal glycoalkaloid (SGA) toxicants in potatoes affects food quality and safety. High levels of SGAs hamper breeding efforts to develop new varieties of potatoes with improved agronomic and post harvest properties. To speed breeding efforts for reducing SGAs in breeding lines and correcting flawed selections we are taking a molecular genetic approach to reduce SGAs. A cDNA encoding a solanidine glucosyltransferase (SGT) was isolated and used to construct antisense transgenes transcribed from either the Cauliflower Mosaic Virus 35S or a tuber-specific granule bound starch synthase promoter. Selected transgenic lines of potato (Solanum tuberosum) cultivar Lenape containing these transgenes exhibit phenotypes with significantly lower SGAs. Field trails over several years in Idaho and Wisconsin resulted in reproducible and statistically significant reductions of up to 40% of tuber SGAs. Although reduction in SGAs is accompanied by expression of Sgt antisense RNA transcripts and a reduction in SGT protein levels, this reduction is likely due entirely to somaclonal variation. Analysis of transgenic cultivar Desiree lines expressing an antisense Sgt revealed essentially complete down-regulation of solanine biosynthesis in several transgenic lines. Chaconine accumulation in these lines was not significantly affected suggesting an unexpected in vivo function of SGT as a g-solanine glucosyltransferase. Additional transgenes encoding SGT and other SGA related sequences are currently being evaluated.