STRUCTURAL ORGANIZATION OF TRANSGENE LOCI IN HEXAPLOID OAT

Department of Agronomy and Plant Genetics, University of Minnesota, 411 Borlaug Hall, 1991 Upper Buford Circle, St.Paul, MN 55108

The internal structure of transgene loci in 16 independent transgenic oat (Avena sativa L.) lines produced by microprojectile bombardment was characterized using Southern blot analysis and fluorescence in situ hybridization (FISH) on metaphase and prophase chromosomes, and on extended DNA fibers. Transgene integration sites exhibited different levels of structural complexity ranging from two copies of the transgene to tightly linked clusters of multiple copies of transgene interspersed with long fragments of oat DNA. The size of these interspersions was estimated from FISH results on prometaphase chromosomes in several lines to be up to a few megabases long indicating that some transgene loci were significantly larger than previously determined by Southern analysis. Fiber FISH showed that within the clusters, transgenes were arranged in long arrays of 6-10 copies. Six of the 25 transgene loci were associated with rearranged chromosomes. These results suggest that particle bombardment-mediated transgene integration may either result from or cause chromosomal breakage and rearrangements.