Eric Lam Laboratory

The goals of the project are:
  1) to obtain a global view of "position effects" in the Arabidopsis chromosomes.
  2) to identify the three dimensional (3-D) positions of genes of interest in interphase nuclei.

       In the phenomenon known as position effect, sites of integration affect the expression levels of transgenes. For instance, a transgene that is highly expressed when integrated into euchromatic regions may be poorly expressed when inserted into heterochromatic regions. Recent studies suggest that chromosomes in interphase nuclei are highly organized, and that the 3-D positions of genes in the interphase nuclei may influence their expression.

       In order to globally sample the position effects, we are generating over 15,000 Ds-tagged lines of Arabidopsis. The Ds-tagging cassette contains a CAMV35S::luciferase which allows monitoring of position effects, and a lac operator repeat (array) which allows the tagged loci to be visualized by expressing fusions of fluorescent-proteins with lacI within the nuclei of live plants. We are mapping the tagged loci with the goal of selecting 3,000 lines in which tagged loci occur on average once every 40 kbp. The selected lines will be used to evaluate the position effects. We are also generating a set of anchoring lines comprising transgenic Arabidopsis lines which would contain two tagged loci that can be visualized with autofluorescent proteins of distinct spectral properties. These "anchoring lines" will be crossed to the Ds-tagged lines in order to compare the organization and dynamic properties of these Ds-tagged loci in interphase nuclei using a three-color system.