REDUCED POSITION EFFECT IN MATURE TRANSGENIC PLANTS CONFERRED BY THE CHICKEN LYSOZYME MATRIX-ASSOCIATED REGION

Matrix-associated regions may be useful for studying the role of chrom atin architecture in transgene activity of transformed plants. The chi cken lysozyme A element was shown to have specific affinity for tobacc o nuclear matrices, and its influence on the variability of transgene expression in tobacco plants was studied. T-DNA constructs in which th is element flanked either the beta-glucuronidase (GUS) reporter gene o r both reporter and selection gene were introduced in tobacco. The var iation in GUS gene activity was reduced significantly among mature fir st-generation transgenic plants carrying the A element. Average GUS ac tivity became somewhat higher, but the maximum attainable level of gen e expression was similar for all three constructs. Transient gene expr ession assays showed that the A element did not contain general enhanc er functions; therefore, its presence seemed to prevent the lower leve ls of transgene expression. The strongest reduction in variability was found in plants transformed with the construct carrying the A element s at the borders of the T-DNA. In this population, expression levels b ecame copy number dependent. The presence of two A elements in the T-D NA did not interfere with meiosis.