Submitted to: American Journal of Potato Research
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/8/2008
Publication Date: 6/1/2008
Citation: Rockhold, D.R., Chang, S., Taylor, N., Allen, P.V., Mc Cue, K.F., Belknap, W.R. 2008. Structure of two solanum bulbocastanum polyubiquitin genes and expression of their promoters in transgenic potatoes. American Journal of Potato Research. 85:219-226. Interpretive Summary: This paper describes the isolation of transcriptional control elements (promoters) from the wild potato species Solanum bulbocastanum, and demonstrates their use in directing the expression of a foreign genes in potato plants. The bul409 and bul427 genes are from the ubiquitin gene family, a family of natural gene fusions. In this paper the bul409 and bul427 genes were used to construct chimeric genes containing foreign marker gene ß-glucuronidase. When introduced back into the potato, these genes have expression patterns similar to the native genes in that expression is wound induced in tubers. These promoter elements should be useful in constructing a wide variety of transgenes to improve the performance of dicotyledonous crop plants.
Technical Abstract: Two polyubiquitin genes, bul409 and bul427, were isolated from a Solanum bulbocastanum Bacterial Artificial Chromosome library. The bul409 and bul427 genes encode hexameric and heptameric polyproteins respectively. The bul427 gene exhibits a number of features suggesting that it represents a pseudogene. The last ubiquitin monomer of this gene is interrupted by a frame shift mutation and the coding sequence is flanked by mitochondrial and chloroplast sequences and a protein kinase pseudogene in close proximity, suggesting that bul427 may be a polyubiquitin pseudogene. However, characterization of cDNAs amplified using bul427-based primers demonstrated that this gene is transcriptonally active. Chimeric transgenes encoding b-glucuronidase (GUS) translationally fused to the first ubiquitin-coding units of both genes were constructed and introduced into potato. Both S. bulbocastanum promoters were efficiently transcribed in transgenic potato leaves, were wound-induced in tubers and resulted in GUS expression levels higher than that obtained with the Cauliflower Mosaic Virus 35S promoter.