Corn Line 98140

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Corn Line 98140 is a variety of genetically engineered corn made by Pioneer Hi-Bred that was deregulated in the U.S. in 2009. It has been genetically engineered to survive being sprayed with the herbicide glyphosate (the active ingredient in Monsanto's herbicide Roundup) and acetolactate synthase (ALS)-inhibiting herbicides. Herbicide tolerant crops and genetically modified organisms are controversial around the world.


On June 1, 2007, Pioneer Hi-Bred International submitted a petition to deregulate "transformation event 98140" to the USDA Animal and Plant Health Inspection Service (APHIS). Specifically, they requested "an extension of the determination of nonregulated status issued previously for Roundup Ready corn line DP-098140-6." On , the USDA published a notice in the Federal Register that an environmental assessment was available for review, soliciting public comments. The USDA conducted an environmental assessment (EA) under the National Environmental Policy Act (NEPA) and issued a "finding of no significant impact" (FONSI). DP-098140-6 was deregulated on December 9, 2009.

At the time of deregulation, the USDA wrote in the Federal Register:

"The 98140 corn line has been genetically engineered to express modified glyphosate acetyltransferase (GAT4621) and modified maize acetolactate synthase (ZM-HRA) proteins. The GAT4621 protein, encoded by the gat4621 gene, confers tolerance to glyphosate-containing herbicides by acetylating glyphosate and thus rendering it non-phytotoxic. The ZM-HRA protein, encoded by the zm-hra gene, confers tolerance to the ALS-inhibiting class of herbicides (e.g. sulfonylureas and imidazolinones). Expression of the zm-hra gene is controlled by the maize ALS (acetolactate synthase) promoter. ALS is the enzyme required for the production of essential branched-chain amino acids such as valine, leucine, and isoleucine. The gat4621 gene is based on the sequences of three gat genes from Bacillus licheniformis, a common soil bacterium. Expression of the gat4621 gene is driven by the corn ubiquitin promoter (ubiZM1). The zm-hra gene was made by isolating the herbicide sensitive maize ALS gene and introducing two specific changes known to confer herbicide tolerance to tobacco ALS.
"The genetic insert also contains the terminator sequence from Solanum tuberoslum (potato) and two sequences from two prevalent plant pests, cauliflower mosaic virus (ehhancer) and Agrobacterium tumefaciens (border region). All of these sequences are well-characterized and are non-coding regulatory regions only. Therefore, these sequences will not cause the 98140 corn line to promote plant disease.
"A single copy of these genes and other DNA regulatory sequences were introduced into the corn genome with the transformation vector PHP24279 using disarmed (non-plant pest causing) A. tumefaciens transformation of immature embryos. Plant cells containing the introduced DNA were selected by culturing in the presence of glyphosate. After the initial transformation, the antibiotic carbenicillin was included in the culture medium to kill any remaining Agrobacterium. Therefore, no part of the plant pest. A tumefaciens remains in the Pioneer HT corn due to the transformation method."[1]

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  1. Federal Register, Vol. 74, No. 235, December 9, 2009.

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