TC1507 Corn Event Detection Using Flanking Sequence Primers
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Solution Overview
Problem
Current methods for detecting specific transgenic events in crops, such as corn plant TC1507, are not discriminative enough, particularly when using DNA constructs that share similar sequences, making it difficult to identify and differentiate between different events, which is crucial for regulatory compliance, environmental monitoring, and ensuring consistent transgene expression.
Innovation Solution
A DNA construct, PHI8999A, is introduced into corn plants, comprising two transgene expression cassettes, including the Cry1F gene for insect resistance, and specific primer sequences are developed to recognize unique 5′ and 3′ flanking sequences of TC1507, allowing for precise identification using PCR and hybridization methods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional DNA detection methods are used to detect transgenic events in corn, then detection can be performed, but the detection precision is insufficient to discriminate between similar sequences of different events
Solution Approach 1:
The detection method is divided into multiple sequential steps: PCR amplification of specific genomic regions flanking the transgene insertion site, followed by restriction enzyme digestion, and finally gel electrophoresis separation. This segmentation allows each step to contribute to the overall discrimination capability, with the flanking region-specific primers providing event-specific amplification and the restriction enzymes providing additional sequence-specific separation.
Solution Approach 2:
The method uses preliminary PCR amplification with primers designed to bind to unique flanking sequences specific to each transgenic event. This preliminary action amplifies only the region containing the event-specific signature sequences before subsequent analysis steps, enabling discrimination before the final detection step.
2Reliability
If multiple transgenic events with similar sequences are present in crop samples, then regulatory compliance requires identification of each event, but current detection methods cannot reliably distinguish between them
Solution Approach 1:
The method targets specific local regions of the genome - the flanking sequences immediately adjacent to the transgene insertion site. These flanking regions have unique sequences that differ between events, even when the transgene itself is identical. By focusing detection on these local unique regions rather than the entire transgenic construct, the method achieves reliable event discrimination.
Solution Approach 2:
Restriction enzymes are used as intermediaries to digest the PCR amplification products at specific recognition sites within the flanking regions. Different events have different restriction site patterns in their flanking sequences, and the enzymes mediate the creation of distinct fragment patterns that can be visually separated and identified on gels.
3Ease of manufacture
If DNA constructs sharing similar sequences are used to confer insect resistance, then genetic engineering efficiency is improved, but the ability to detect and differentiate specific events is reduced
Solution Approach 1:
Instead of trying to differentiate events based on the transgene sequence itself (one dimension), the method shifts to analyzing the flanking genomic sequences (another dimension). The flanking regions provide an additional layer of information that is unique to each integration event, enabling discrimination even when the transgene sequences are identical or very similar.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enables reliable detection of TC1507 in biological samples, ensuring compliance with regulations and maintaining consistent transgene expression, thereby facilitating the production of insect-resistant corn plants with improved agronomic performance.
Implementation Method 1
contacting the sample with a DNA primer set, that when used in a nucleic acid amplification reaction produces an amplicon that is diagnostic for corn event TC1507
Implementation Method 2
performing a nucleic acid amplification reaction, thereby producing the amplicon
Data Source
AI summary
The invention provides DNA compositions that relate to transgenic insect resistant maize plants. Also provided are assays for detecting the presence of the maize TC1507 event based on the DNA sequence of the recombinant construct inserted into the maize genome and the DNA sequences flanking the insertion site. Kits and conditions useful in conducting the assays are provided.