Submitted to: Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/17/2004
Publication Date: 9/11/2004
Citation: Mc Cue, K.F., Sheperd, L., Allen, P.V., Maccree, M.M., Rockhold, D.R., Corsini, D.L., Davies, H.V., Belknap, W.R. 2004. Metabolic compensation of steroidal glycoalkaloid biosynthesis in transgenic potato tubers: using reverse genetics to confirm the in vivo enzyme function of a steroidal alkaloid galactosyltransferase. Plant Science. 168(1):267-273. Interpretive Summary: Steroidal glycoalkaloids (SGAs) are plant metabolites found in Solanaceous plants including the potato and tomato. Potatoes produce two major SGAs species, a-chaconine and a-solanine. As part of a program to improve potato cultivars with molecular genetics we are using a potato gene solanidine glucosyltransferase (SGT) to engineer lower levels of SGAs. Introduction of the SGT gene into potatoes resulted in a lack of a-solanine accumulation and elevated levels of a-chaconine, resulting in unchanged total SGA levels in selected transgenic lines. The results indicate that the actual function of the SGT gene in the plant was different than previously demonstrated in the laboratory. This illustrates the need to accompany laboratory studies with studies in plants when assigning functions to new genes.
Technical Abstract: Steroidal glycoalkaloids (SGAs) are secondary metabolites of Solanaceous plants. Two predominant glycoalkaloids, a-chaconine and a-solanine are produced in Potatoes. An antisense transgene was constructed to down-regulate glycoalkaloid biosynthesis using a potato cDNA encoding a solanidine glucosyltransferase (SGT1). Introduction of this construct into potatoes resulted in an almost complete inhibition of a-solanine accumulation and elevated levels of a-chaconine, resulting in wild type total SGA levels in the transgenic lines. The results indicate that while SGT1 encodes an enzyme capable of solanidine glucosyltransferase activity in vitro, its role in vivo is glucosylation of g-solanine. This illustrates that assignment of gene function by in vitro testing must be confirmed by in vivo studies to verify physiological function.