|Joung, Young Hee -|
Submitted to: Floriculture, Ornamental and Plant Biotechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 5, 2009
Publication Date: November 15, 2009
Citation: Kamo, K., Joung, Y.H., Green, K. 2009. GUS expression in Gladiolus plants controlled by two Gladiolus ubiquitin promoters. Floriculture and Ornamental Biotechnology. 3:10-14. Interpretive Summary: Genetic engineering offers the opportunity to develop flower bulb crops that are resistant to their two main pathogens, viruses and fungi. It is increasingly difficult to control these pathogens as many of the pesticides previously used have been banned. Successful genetic engineering depends on the availability of promoters that result in sufficient levels of transgene expression and in the desired tissues where the pathogen attacks. We have been conducting genetic engineering experiments with Gladiolus and have found that the corn ubiquitin promoter that is commonly used for genetic engineering of monocot crops such as corn, rice, and wheat does not result in high levels of gene expression in Gladiolus. Two ubiquitin promoters have been isolated from Gladiolus and characterized in transgenic plants of Gladiolus using the GUS reporter gene. Both promoters were found to express at higher levels in roots and callus cells than in leaves. Although plants developed with the CaMV 35S promoter resulted in higher levels of GUS expression in Gladiolus than the Gladiolus ubiquitin promoters, these two promoters resulted in normal plant growth as compared to that with the CaMV 35S promoter so they maybe useful for genetic engineering of Gladiolus.
Technical Abstract: Ubiquitin represents a conserved family of genes that is involved in many metabolic processes. The most commonly used promoter for genetic engineering of cereal monocots is the maize ubiquitin promoter because it directs high levels of expression in most of the plant’s tissues, but this promoter results in low levels of expression in Gladiolus. Several ubiquitin promoters were isolated from Gladiolus to find one that directs higher levels of expression than the maize ubiquitin promoter in Gladiolus. Two ubiquitin promoters isolated from Gladiolus, GUBQ2 and GUBQ4, are characterized here for their levels of expression and tissue-specific location of expression when transformed into Gladiolus. Gladiolus cv. Jenny Lee plants were transformed with the uidA gene coding for ß-glucuronidase (GUS) expression under control of either the GUBQ2 or GUBQ4 ubiquitin promoters. Five plant lines with either the GUBQ2 or GUBQ4 promoter were confirmed to be independently transformed by Southern hybridization. Two plant lines each contained one copy of pGUBQ2, and the other lines with either promoter were multicopy. There was a range in the levels of GUS expression. One of the GUBQ4 lines appeared to be silenced as GUS was not expressed in their young leaves, young roots, and callus derived from the plants. Levels of GUS expression were higher in young roots than in young shoots and callus with the GUBQ2 promoter. Three of the four expressing lines with GUBQ4 showed the highest levels of GUS expression in callus followed by roots. Histochemical staining showed that GUS was expressed throughout the leaves and roots of Gladiolus plants transformed with either GUBQ2 or GUBQ4.