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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
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.
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.
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
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
9. Environmental Releases Database for the U.S. 2005
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