The role of cell differentiation state and HMG-I/Y in the expression of transgenes flanked by matrix attachment regions

• Published in: Transgenic research 2001-10, Vol.10 (5), p.465-470
• Main Authors: ASCENZI, Robert, INGRAM, Jennifer L, MASSEL, Mara, THOMPSON, William F, SPIKER, Steven, WEISSINGER, Arthur K
• Format: Article
• Language: English
• Subjects: Biological and medical sciences; Biotechnology; Cell Differentiation; Cells, Cultured; Fundamental and applied biological sciences. Psychology; Gene Expression; Genes; Genetic engineering; Genetic technics; gus gene; high mobility group protein I/Y; HMGA1a Protein - genetics; HMGA1a Protein - metabolism; Methods. Procedures. Technologies; Molecular weight; Nicotiana - cytology; Nicotiana - genetics; Nicotiana tabacum; Plants, Genetically Modified; Transgenic animals and transgenic plants; Transgenic plants
• ISSN: 0962-8819; 1573-9368
• DOI: 10.1023/A:1012082602587

The tobacco nuclear matrix attachment region (MAR), RB7, has been shown to have a much greater effect on transgene expression in cultured cells than in transgenic plants. This is comparable to work in mouse systems showing that MARs have a positive effect on transgene expression in embryonic tissues but not adult tissues. There are several possible explanations for these observations. One is that cell differentiation state and proliferation rate can affect MAR function. We tested this possibility by initiating suspension cell cultures from well-characterized transgenic plants transformed with 35S::GUS with and without flanking MARs and then comparing GUS specific activity in the cell lines to those of the transgenic plants from which the cell lines were derived. If cell differentiation state and proliferation rate do affect MAR function, we would expect the ratio of transgene expression (cell suspensions : plants) to be greater in MAR lines than in control lines. This turned out not to be the case. Thus, it appears that MAR function is not enhanced simply because cells in culture divide rapidly and are not differentiated. Because in animal systems the chromosomal protein HMG-I/Y has been shown to be upregulated in proliferating cells and may have a role in MAR function, we have also examined the levels of the tobacco HMG-I/Y homolog by immunoblotting. The level of this protein does not differ between primary transformant cultured cells (NT-1) and Nicotiana tabacum plants (SR-1). However, a higher molecular weight cross-reacting polypeptide was found in nuclei from the NT-1 cell suspensions but was not detected in SR-1 leaf nuclei or cell suspensions derived from the SR-1 plants.