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 b-casein under the control of the soybean lectin 5 0 and 3 0 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 T 1 and T 2 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.

Editor’s Choice: Crop Genome Plasticity and Its Relevance to Food and Feed Safety of Genetically Engineered Breeding Stacks

“…In general, single-copy transgenic insertions and their flanking regions are more stable than complex insertions with duplicated sequences (Papazova et al, 2006(Papazova et al, , 2008Kohli and Christou, 2008), as the latter can undergo homologous recombination with resulting loss of function (Choffnes et al, 2001). In this regard, the behavior of multiple copies of a given transgenic insertion is similar to that of repetitive DNA in general or that of naturally occurring duplicated genes (e.g.…”

Unintended consequences of plant transformation: A molecular insight

“…These factors include transgene deletion, duplication and rearrangement (reviewed by Yin et al 2004). These phenomena may be partly explained by rare occurrences of meiotic or mitotic recombination events, which have been observed in tobacco and soybean (Tovar and Lichtenstein 1992;Choffnes et al 2001). Transgene stability may also depend on the plant species.…”

Agrobacterium-Mediated Transformation of Indonesian Orchids for Micropropagation

“…The greatest motivation for using Agrobacterium appears to be molecular and cytogenetic analyses showing that higher frequencies of transgene loci produced by microprojectile bombardment and other direct DNA delivery methods are more complex compared to transgene loci produced via Agrobacterium (Pawlowski and Somers, 1996). Complex transgene loci are associated with problems of transgene expression (Finnegan and McElroy, 1994;Matzke and Matzke, 1995;Pawlowski et al, 1998;Kohli et al, 1999) and inheritance (Christou et al, 1989;Choffnes et al, 2001). In other words, Agrobacterium-mediated transformation is a simple and inexpensive method that produces the simplest transgene locus structure.…”