title: Reduced Position Effect in Mature Transgenic Plants Conferred by the Chicken Lysozyme Matrix-Associated Region.
abstract: Matrix-associated regions may be useful for studying the role of chromatin architecture in transgene activity of transformed plants. The chicken lysozyme A element was shown to have specific affinity for tobacco nuclear matrices, and its influence on the variability of transgene expression in tobacco plants was studied. T-DNA constructs in which this element flanked either the [beta]-glucuronidase (GUS) reporter gene or both reporter and selection gene were introduced in tobacco. The variation in GUS gene activity was reduced significantly among mature first-generation transgenic plants carrying the A element. Average GUS activity became somewhat higher, but the maximum attainable level of gene expression was similar for all three constructs. Transient gene expression assays showed that the A element did not contain general enhancer functions; therefore, its presence seemed to prevent the lower levels of transgene expression. The strongest reduction in variability was found in plants transformed with the construct carrying the A elements at the borders of the T-DNA. In this population, expression levels became copy number dependent. The presence of two A elements in the T-DNA did not interfere with meiosis.
authors.affiliation: Department of Molecular Biology, Centre for Plant Breeding and Reproduction Research (CPRO-DLO), P.O. Box 16, NL-6700 AA Wageningen, The Netherlands.
authors.forename: L.
authors.initials: L
authors.lastname: Mlynarova
authors.forename: A.
authors.initials: A
authors.lastname: Loonen
authors.forename: J.
authors.initials: J
authors.lastname: Heldens
authors.forename: R. C.
authors.initials: RC
authors.lastname: Jansen
authors.forename: P.
authors.initials: P
authors.lastname: Keizer
authors.forename: W. J.
authors.initials: WJ
authors.lastname: Stiekema
authors.forename: J. P.
authors.initials: JP
authors.lastname: Nap