Effect of nuclear matrix attachment regions on transgene expression in tobacco plants

Matrix attachment regions (MARs) are thought to participate in the organiza tion and segregation of independent chromosomal loop domains. Although ther e are several reports on the action of natural MARs in the context of heter ologous genes in transgenic plants, in our study we tested a synthetic MAR (sMAR) with the special property of unpairing when under superhelical strai n, for its effect on reporter gene expression in tobacco plants. The synthe tic MAR was a multimer of a short sequence from the MAR 3 ' end of the immu noglobulin heavy chain (IgH) enhancer. This sMAR sequence was used to flank the beta -glucuronidase (GUS) reporter gene within the T-DNA of the binary vector pBI121. Vectors with or without the sMARs were then used to transfo rm tobacco plants by Agrobacterium tumefaciens. Transgenic plants containin g the sMAR sequences flanking the GUS gene exhibited higher levels of trans gene expression compared with transgenic plants which lacked the sMARs. Thi s effect was observed independently of the position of the sMAR at the 5 ' side of the reporter gene. However, variation of the detected transgene exp ression was significant in all transformed plant populations, irrespective of the construct used.