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Re: [SANET-MG] LLRIC601



Phosphinothricin, the active ingredient of glufosinate ammonium, inhibits glutamine synthetase, which results in the accumulation of lethal levels of ammonia in susceptible plants within hours of application. Plants produce ammonia as a result of normal metabolic processes.

Hi Greg,
The material below from the Canadian Food Inspection Service helps to explain about BAR and PAT. It is noteworthy that PAT used in safety studies came from bacterial cultures not rice plants. Hope this helps, cheers, joe cummins The bar gene engineered into LLrice62 codes for the production of the enzyme Phosphinothricin Acetyl-Transferase (PAT) which acetylates glufosinate ammonium, thereby detoxifying the herbicide, conferring herbicide resistance to the rice plant. PAT has extremely high substrate specificity.

The introduced bar gene was originally isolated from Streptomyces hygroscopicus, a common gram-positive soil-borne bacterium. The PAT enzyme is therefore naturally occurring in the soil. More generally, acetyltransferases are ubiquitous in nature.

The bar gene expressed in event LLrice62 is linked to a constitutive promoter (i.e. results in expression in all rice tissues). PAT protein expression was determined from plants grown in Crowley, Louisiana in 1998. Mean protein expression in event LLrice62 was 12.1 µg/g fresh weight, 75.3 µg/g fresh weight, 1.56 µg/g fresh weight, 12.7 µg/g fresh weight, 30.9 µg/g fresh weight, 84.7 µg/g fresh weight in grain, straw, rice hulls, roots, stems, and leaves respectively.

Protein allergens are normally resistant to digestion unlike the PAT protein, which was shown to degrade readily in simulated gastric fluid within 30 seconds and simulated intestinal fluid within 5 minutes. Unlike many known allergens the PAT protein is not glycosylated and is present at low levels (0.02% in grain, 0.32% in straw). Using sera from patients with known rice allergen sensitivity, it was demonstrated that levels of endogenous rice allergens were comparable between the modified rice and the unmodified parent.

A search for amino acid sequence similarity between the PAT protein and known allergens and toxins, using a database assembled from the public domain databases SwissProt, trEMBL, GeneSeq-Prot, PIR, PDB, DAD and GenPept, revealed no overall homology (based on 35% identity on a window of 80 amino acids). PAT only had high similarity with other acetyltransferase proteins. Additionally, no significant epitope similarities between the PAT protein and known allergens (based on 100% sequence identity of 8 or more contiguous amino acids) were found.

Due to the low levels of PAT protein expressed in the rice plant, it was necessary to produce PAT protein by bacterial fermentation to obtain sufficient quantities to conduct some studies. The bacterially produced protein was compared to the plant produced protein and shown to be of similar molecular weight and immunological reactivity. Neither the plant nor bacterially expressed PAT is glycosylated.

Raquel & Greg wrote:
Hi Joe. What is the mechanism by which the bar gene confers glufosinate resistance in plants? What does the PAT protein actually do?

Thanks,
Greg

----- Original Message ----- From: "jcummins" <jcummins@UWO.CA>
To: <SANET-MG@LISTS.IFAS.UFL.EDU>
Sent: Saturday, September 09, 2006 2:57 PM
Subject: [SANET-MG] LLRIC601


The Bayer LLRICE601 USDA Extension Petition on the USDA/APHIS website is 85 pages long. About 10 pages deal with administration . Off the remaining 72 pages 25 pages are all or nearly completely blank , designated CBI. The earlier petition on rice was much longer and had no pages designated CBI. The areas designated CBI are the areas of the DNA sequence allowing independent measurements. As well the earlier test sites for LLRICE601 appear to all have been designated CBI as were the trial results. In previous petitions USDA has not allowed such crude use of CBI. Bayer and its lawyers seem to have gone CBI berserk but USDA did not have to allow them that insult to the public. It is nearly impossible to make any judgment about the rice and its contamination due to the cloud of CBI.. More disturbingly, USDA seems to be a co-conspirator in withholding essential information from the world. sadly

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