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[SANET-MG] synthetic genes and peptides



Cecropin peptides have begun to be tested as spray applications, has there been thought about the use of such toxins in organic agriculture?
July 26, 2005
Prof. Joe Cummins
“Genes for synthetic peptides provide protection from microbial pests”
Anti-microbial peptides provide the first line of defense against microbial predators in organisms in both the vegetal and animal kingdoms. The peptides are involved in innate immunity The peptides are 15 to 40 amino acids in length, most are hydrophobic and cationic. They provide protection from bacteria, fungi and viruses , they mainly act oat the cell membrane of cellular pathogens (1,2). The peptides are beginning to be employed in medicine and in crop protection. A synthetic peptide based on the cecropin B petide toxin (cecropin is a product obtained from the moth, Cecropia) was called D4E1. It is a linear peptide with 17 amino acids whose sequence is FKLRAKIKVRLRAKIKL in a beta sheet configuration. The peptide was active against Aspergillus and Fusarium fungi. The peptide acted by binding to ergosterol, a sterol present in fungal cell walls (3). D4E1 proved proved to have broad spectrum antimicrobial action. It proved active against the fungal orders Ascomycete, Basidiomycete, Deuteromycete and Oomycetes , along with bacterial pathogens from Psuedomonas and Xanthomonas (4). The D4E1 toxin proved effective in treatment of human Chlamydia infection (5). Transgenic tobacco plants were transformed with a gene for the peptide D4E1 driven by a double CaMV promoter and terminated by the nos transcription terminator accompanied by a kanamycin resistance marker. The transgenic tobacco was resistant to fungal pathogens (6). Poplar trees transformed as in the transgenic tobacco was resistant to bacterial pathogens A. tumefacians and X. populi but were not resistant to a fungal pathogen Hypoxylon mammatum (7). Cotton plants transformed with the gene for D4E1 as in the previous studies showed resistance to fungi including Fusarium, Verticillium and Aspergillus, the synthetic peptide was proposed to be effective against mycotoxin-causing fungal pathogens (8). Field tests have been conducted on D4E1 transgenic cotton in Arizona and California while D4E1 transformed potatoes were tested in Idaho (9). It seems imperative that petitions to remove the transgenic crops containing D4E1 from regulation are not far off. Since the D4E1 and its peptide product are both fully synthetic it will be a stretch to assume that the product is “substantially equivalent” to the natural product. For that reason the transgenic crops must be subject to a full range of acute and chronic toxicological tests, including comprehensive cancer tests. The United States EPA Scientific Advisory Panels (SAPs) do not appear to have dealt with the synthetic antimicrobial peptides as crop transgenes. Pessimistically, the SAPs are likely to defy logic and assume that the synthetic genes and peptides are substantially equivalent to natural products and do not require comprehensive testing. This will happen , unless the public are aware and insure that the synthetic genes and peptides are tested comprehensively. When the time comes the public voice must be heard to demand comprehensive testing of synthetic genes and peptides.
References
1. Bulet P, Stocklin R. and Menin L. Anti-microbial peptides: from invertebrates to vertebrates Immunol Rev. 2004 ,198,169-84 2. Boman, H. Antibacterial peptides: basic facts and emerging concepts J Intern Med. 2003 ,254(3):197-215 3. De Lucca AJ, Bland JM, Grimm C, Jacks TJ, Cary JW, Jaynes JM, Cleveland TE and Walsh TJ. Fungicidal properties, sterol binding, and proteolytic resistance of the synthetic peptide D4E1. Can J Microbiol. 1998 ,44,514-20 4. Rajasekaran K, Stromberg KD, Cary JW and Cleveland TE. Broad-spectrum antimicrobial activity in vitro of the synthetic peptide D4E1 J Agric Food Chem. 2001,49,2799-803 5. Ballweber LM, Jaynes JE, Stamm WE and Lampe MF. In vitro microbicidal activities of cecropin peptides D2A21 and D4E1 and gel formulations containing 0.1 to 2% D2A21 against Chlamydia trachomatis. Antimicrob Agents Chemother. 2002 ,46,34-41 6. Cary JW, Rajasekaran1 K, Jaynes JM and Cleveland TE. Transgenic expression of a gene encoding a synthetic antimicrobial peptide results in inhibition of fungal growth in vitro and in planta. Plant Sci. 2000 ,29,154,171-181 7. Mentag R, Luckevich M, Morency MJ and Seguin A. Bacterial disease resistance of transgenic hybrid poplar expressing the synthetic antimicrobial peptide D4E1. Tree Physiol. 2003 ,23,405-11 8. Rajaskaran,K,Cary,J,Jaynes,J. and Clevland,T. Disease resistance conferred by the expression of a gene encoding a synthetic peptide in transgenic cotton (Gossypium hirsutumL.) plants Plant Biotechnology Journal 2005,3 in press
     doi: 10.1111/j.1467-7652.2005.00145
9. Environmental Releases Database for the U.S. 2005 http://www.nbiap.vt.edu/cfdocs/fieldtests3.cfm









	

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