Use of two-color fluorescence-tagged transgenes to study interphase chromosomes in living plants.

Sixteen distinct sites distributed on all five Arabidopsis (Arabidopsis thaliana) chromosomes have been tagged using different fluorescent proteins and one of two different bacterial operator-repressor systems: (1) a yellow fluorescent protein-Tet repressor fusion protein bound to tet operator sequences, or (2) a green or red fluorescent protein-Lac repressor fusion protein bound to lac operator sequences. Individual homozygous lines and progeny of intercrosses between lines have been used to study various aspects of interphase chromosome organization in root cells of living, untreated seedlings. Features reported here include distances between transgene alleles, distances between transgene inserts on different chromosomes, distances between transgene inserts on the same chromatin fiber, alignment of homologous chromosomes, and chromatin movement. The overall findings are consistent with a random and largely static arrangement of interphase chromosomes in nuclei of root cells. These transgenic lines provide tools for in-depth analyses of interphase chromosome organization, expression, and dynamics in living plants.