A transgenic locus in soybean exhibits a high level of recombination

Abstract

We have examined transgene inheritance in over 300 progeny of a line of soybean (Glycine max) transformed by particle bombardment with a construct containing bovine β-casein under the control of the soybean lectin 5′ and 3′ regulatory elements. Four copies of the casein transgene, located at a single locus, exhibit a high frequency of recombination that resulted in novel patterns in approximately 16% of the progeny in both the T1 and T2 generations. Characterization of the transgene locus using restriction enzymes that do not cut the transformation plasmid showed that all four transgene copies are at a single locus no larger than approximately 40 kb in size. Therefore, the recombination events resulting in the loss of transgene DNA are taking place within a limited physical distance on the host chromosome. This is the first report extensively documenting transgene instability at the DNA level in a plant transformed via particle bombardment. As this report indicates, a seemingly simple phenotype (presence of the foreign protein) may conceal inherent genetic instability at the DNA level.