Detection of RNA variants transcribed from the transgene in Roundup Ready soybean

Abstract

The acreage for genetically modified crops (GMOs)—particularly soybean—has steadily increased since 1996, when the first crop of Roundup Ready soybean (intended for food production) was grown. The Roundup Ready soybean varieties derive from a soybean line into which a glyphosate-resistant enolpyruvylshikimate-3-phosphate-synthase (EPSPS) gene was introduced. The inserted and the flanking regions in Roundup Ready soybean have recently been characterized. It was shown that a further 250-bp fragment of the epsps gene is localized downstream of the introduced nos terminator of transcription, derived from the nopaline synthase gene from Agrobacterium tumefaciens. We examined whether this 250-bp fragment could be of functional importance. Our data demonstrate that at least 150 bp of this DNA region are transcribed in Roundup Ready soybean. Transcription of the fragment depends on whether read-through events ignore the nos terminator signal located upstream. Our data also indicate that the read-through product is further processed, resulting in four different RNA variants from which the transcribed region of the nos terminator is completely deleted. Deletion results in the generation of open reading frames which might code for (as yet unknown) EPSPS fusion proteins. The nos terminator is used as a regulatory element in several other GMOs used for food production. This implies that read through products and transcription of RNA variants might be a common feature in these GMOs.