Database Product Description
- Host Organism
- Zea mays (Maize)
- Trade Name
- Roundup Ready®
- Glyphosate herbicide tolerance.
- Trait Introduction
- Microparticle bombardment of plant cells or tissue
- Proposed Use
Production for human consumption and livestock feed.
- Product Developer
- Monsanto Company
Summary of Regulatory Approvals
Corn line NK603 was developed to allow the use of the herbicide glyphosate as a weed control option in corn. The gene conferring tolerance to glyphosate was introduced via genetic engineering techniques. These techniques enable the developer to express in the corn plant the 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) gene, which is involved in the synthesis of aromatic amino acids. This gene, isolated from Agrobacterium tumefaciens strain CP4 (CP4 EPSPS), encodes a version of the enzyme that is tolerant to concentrations of glyphosate that would normally inhibit the activity of the endogenous corn enzyme. The CP4 EPSPS gene and regulatory sequences controlling its expression were introduced via biolistic particle bombardment.
Line NK603 was produced from a proprietary inbred line designated as AW x CW using particle acceleration. NK603 contains two plant expression cassettes each containing a single copy of the CP4 EPSPS gene and respective regulatory sequences as follows:
CP4 EPSPS Cassette 1 contains the CP4 EPSPS gene under the control of the rice actin 1 promoter (McElroy et al. 1990) and the CTP2 chloroplast transit peptide leader sequence from Arabidopsis thaliana (Klee and Rogers 1987). The purpose of this latter sequence is to direct CP4 EPSPS protein to the chloroplast, which is the site of aromatic amino acid synthesis. The CP4 EPSPS gene sequence was modified slightly, but retains greater than 99.4% homology to the native Agrobacterium gene. The NOS 3’ nontranslated region of the nopaline synthase gene from Agrobacterium tumefaciens T-DNA was used to provide the polyadenylation signal.
CP4 EPSPS Cassette 2 contains the CP4 EPSPS gene under the control of the enhanced cauliflower mosaic virus (CaMV) 35S promoter (Kay et al. 1985). The Zmhsp70 intron from the corn hsp70 heat shock protein was included to stabilize the level of transcription (Rochester et al. 1986) and the CTP2 chloroplast transit peptide leader sequence was used to direct the CP4 EPSPS protein to the chloroplast. The NOS 3’ nontranslated region of the nopaline synthase gene from Agrobacterium tumefaciens T-DNA was used to provide the polyadenylation signal.
Roundup ready corn line GA21 was designated as the antecedent organism for NK603, which was not judged to have any characteristics that would pose a greater impact on the environment or non-target organisms.
Kay, R., Chan, A., Daly, M. & McPherson, J. (1985). Duplication of the CaMV 35S promoter sequences creates a strong enhancer for plant genes. Science 236: 1299-1302.
Klee, H.J. & Rogers, S.G. (1987). Cloning of an Arabidopsis gene encoding 5-enolpyruvlyshikimate-3-phosphate synthase: sequence analysis and manipulation to obtain glyphosate-tolerant plants. Mol. Gen. Genet. 210: 437-442.
McElroy, D., Zhang, W., Cao, J. & Wu, R. (1990). Isolation of an efficient actin promoter for use in rice transformation. Plant Cell 2: 163-171.