Abstract
BackgroundThe safety assessment and control of stacked transgenic crops is increasingly important due to continuous crop development and is urgently needed in China. The genetic stability of foreign genes and unintended effects are the primary problems encountered in safety assessment. Omics techniques are useful for addressing these problems. The stacked transgenic maize variety 12–5 × IE034, which has insect-resistant and glyphosate-tolerant traits, was developed via a breeding stack using 12–5 and IE034 as parents. Using 12–5 × IE034, its parents (12–5 and IE034), and different maize varieties as materials, we performed proteomic profiling, molecular characterization and a genetic stability analysis.ResultsOur results showed that the copy number of foreign genes in 12–5 × IE034 is identical to that of its parents 12–5 and IE034. Foreign genes can be stably inherited over different generations. Proteomic profiling analysis found no newly expressed proteins in 12–5 × IE034, and the differences in protein expression between 12 and 5 × IE034 and its parents were within the range of variation of conventional maize varieties. The expression levels of key enzymes participating in the shikimic acid pathway which is related to glyphosate tolerance of 12–5 × IE034 were not significantly different from those of its parents or five conventional maize varieties, which indicated that without selective pressure by glyphosate, the introduced EPSPS synthase is not has a pronounced impact on the synthesis of aromatic amino acids in maize.ConclusionsStacked-trait development via conventional breeding did not have an impact on the genetic stability of T-DNA, and the impact of stacked breeding on the maize proteome was less significant than that of genotypic differences. The results of this study provide a theoretical basis for the development of a safety assessment approach for stacked-trait transgenic crops in China.
Highlights
The safety assessment and control of stacked transgenic crops is increasingly important due to continuous crop development and is urgently needed in China
Molecular characterization of stacked-trait transgenic maize 12–5 × IE034 The multiple PCR detection results showed that all three target genes were integrated in stacked-trait genetically modified (GM) maize lines 12–5 × IE034, 12–5 × IE034-F2 and 12–5 × IE034-F3, and the sizes of the amplified fragments were consistent with those of the DNA fragments in the corresponding parent maize (Fig. 1)
The primers and probes used in this study showed good specificity and were capable of clearly distinguishing positive and negative micro-droplets
Summary
The genetic stability of foreign genes and unintended effects are the primary problems encountered in safety assessment. Stacked genetically modified crops (GMCs) with their improved traits, versatility and low cost, have been well received by many growers and researchers since their inception and are leading transgenic crop developments. Stacked GMCs can be obtained through cotransformation, retransformation and conventional breeding [2, 3]. A stacked GMC that is produced by cotransformation and retransformation requires a de novo safety assessment as a new event [4]. The requirements for the safety assessment of products obtained using conventional breeding stack strategies are not standardized and differ among countries [5,6,7,8,9]. Two primary concerns are 1) whether a breeding stack can increase genomic instability and 2)
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