Abstract
Transgenes stably integrated into chromosome are often silenced, a phenomena is called gene silencing. Gene silencing has been attributed to several factors, including differences in chromosome position, repeat sequences, and copy number. We transformed Arabidopsis plants with pBI121 (CaMV35S-GUS and NOS-NPTII) using Agrobacterium-mediated transformation. We carefully selected ten lines containing single 'complete' (intact, non-truncated, non-rearranged) copies of the transgene located at different chromosome positions. These lines showed very similar levels of transgene expression, and gene silencing was not observed. In a subsequent study, genetic crosses of isolated lines were performed to generate plants harboring one to eight copies of the transgene. We have been investigating whether gene silencing dependent copy number of the transgene is occur.
