A gypsy-like sequence from Arabidopsis thaliana exhibits enhancer-blocking activity in transgenic plants

Strong transcriptional enhancers are known to interfere with expression driven by nearby promoters in artificial systems, which can be a considerable obstacle in the field of transgenic plant technology. Enhancer-blocking insulators are one tool available to prevent such interactions; however, only a handful of sequences exhibiting this function in plants have been identified to date. One of the most extensively characterized enhancer-blocking insulators in metazoan systems is that found within the 5' untranslated region of the gypsy retrotransposon from Drosophila. To determine whether a 2.2-kb gypsy-like element from the Arabidopsis genome (Atgypsy-like) would elicit the same effect in transgenic plants, we conducted enhancer-blocking assays in transgenic Arabidopsis in which this fragment was inserted between the constitutive cauliflower mosaic virus (CaMV) 35S enhancer and petal-and stamen-specific PISTILLATA promoter (PIp). We found that the Atgypsy-like element significantly reduced CaMV 35S enhancer-mediated constitutive activation of the PIp when situated between them, functioning as a true enhancer-blocking insulator that has the potential to be used for the reduction of enhancer-promoter interference between multiple transcriptional units within transgenic vectors in plant species.