|CHHAN, ALYSSA - University Of California
Submitted to: American Journal of Potato Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/28/2011
Publication Date: 12/5/2011
Citation: Mc Cue, K.F., Rockhold, D.R., Chhan, A., Belknap, W.R. 2011. Structure of two solanum tuberosum steroidal glycoalkaloid glycosyltransferase genes and expression of their promoters in transgenic potatoes. American Journal of Potato Research. 88(6):485-492 doi:10.1007/s12230-011-9215-2.
Interpretive Summary: The Sgt gene family in potatoes is a family of proteins involved in the formation of steroidal glycoalkaloids (SGA). SGA accumulate in potato tubers is thought to provide an important flavor element. However, too much SGA and potatoes become bitter. We study these genes to better understand how to control the accumulation of unwanted levels of SGA. These proteins can be very active in the biological processes that result in the accumulation of SGAs. We have therefore chosen members of this gene family to test for the ability of the associated genetic control elements to be very active in the production of enzyme activity of reporter genes. These control elements of these genes were found to provide good reporter gene activity and may therefore be useful in the molecular breeding efforts to improve the agronomic and healthful properties of potatoes. Particularly for those involving potato improvement using only native potato genes, a process called precise breeding or intragenics.
Technical Abstract: The Sgt2 gene in potato encodes a solanidine glucosyltransferase and is present as two distinct alleles expressed in cultivated potatoes. Promoter regions upstream from both steroidal glycoalkaloid biosynthetic gene alleles, Sgt2.1 and Sgt2.2, were isolated from Solanum tuberosum cv. Russet Burbank genomic DNA. Genomic regions were amplified from total DNA using a conserved region in the Sgt2 coding sequences and artificial upstream primers. Clones were sequenced and attributed to each of the alleles. The longest sequences for each allele were used to create b-glucuronidase (GUS) reporter gene fusions and mobilized into stable transgenic lines for analysis of promoter expression in leaves and tubers under control and wounded conditions. S. tuberosum promoters from Sgt2.1 and from Sgt2.1 produced GUS activity in transgenic potato leaves and tubers comparable to GUS activity produced by the CaMV35S promoter. The Sgt2.1 promoter supported higher transgene activity in tubers versus leaves and exhibited small but consistent increases in response to wounding in tubers only. On average the Sgt2.2 promoter exhibited higher activity in both leaves and tubers relative to the Sgt2.1; however, the effect of wounding on GUS activity in both leaves and tubers was inconsistent.