Molecular dissection of the tobacco Rb7 matrix attachment region (MAR): Effect of 5′ half on gene expression in rice

We investigated the effect of tobacco Rb7 Matrix Attachment Region (MAR) sequences on transgene expression in a japonica rice variety TNG67. Six plasmids were constructed and used to transform rice. For each plasmid, over 30 independent transgenic plant lines containing a β-glucuronidase (GUS) gene expression cassette, either by itself, or flanked by a full-length or a half-length tobacco Rb7 MAR sequence were generated, out of which 15 lines were randomly selected and used for detailed analysis. Quantitative GUS activity assay of the transgenic plant lines showed an average 77-fold increase in GUS activity when the Gus gene was flanked by the full-length MAR sequence. The MAR sequence also minimized variations in Gus gene expression in independently produced transgenic plants harboring the same plasmid. The half-length MAR sequence was unable to stimulate Gus gene expression but did retain the ability to reduce variations in the level of expression among different transgenic plants.