|Scientific articles of interest|
Selected and commented by ENTRANSFOOD
Updated March 6, 2002
No gene transfer of foreign gene from genetically modified maize
Genetically modified maize containing an antibiotic resistance gene was fed to chickens. This antibiotic resistance gene may theoretically be transferred from digested maize to intestinal bacteria, which would render these bacteria resistant to antibiotics. In practice, however, no such transfer was found to occur in the intestines of the chickens fed the genetically modified maize.
Reference: P.A. Chambers et al. (2002) The fate of antibiotic resistance marker genes in transgenic plant feed material fed to chickens. Journal of Antimicrobial Chemotherapy 49: 161-164.
Nature Biotechnology’s February 2002 issue features a letter by Piet Schenkelaars, a Dutch scientist, who investigated several dossiers on foods from GM crops approved by the European Union. P. Schenkelaars concludes that there are inconsistencies between the dossiers with regard to the dossier data on composition, including nutrients, antinutrients, and toxins. It is therefore proposed to introduce a minimum list of compounds that should be analysed for GM crops.
Reference: P. Schenkelaars (2002) Rethinking substantial equivalence. Nature Biotechnology 20: 119
Tomatoes with increased levels of carotenoids (provitamin A - like compounds)
Carotenoids, including beta-carotene (provitamin A) and lycopene, were increased in genetically modified tomatoes. This increase was due to an insertion of a bacterial gene for the enzyme phytoene synthase, which was intended to increase the formation of intermediate compounds in the biosynthesis of carotenoids. The profile of the carotenoids in the GM tomatoes was the same as in non-GM tomatoes in that no novel carotenoids had been formed and that the carotenoids occurred in the same proportions with respect to each other.
Reference: P.D. Fraser et al. (2002) Evaluation of transgenic tomato plants expressing an additional phytoene synthase in a fruit-specific manner. Proceedings of the National Academy of Sciences USA, 99: 1092-1097
Maize nutritionally enhanced with milk protein
The protein alpha-lactalbumin (from pig) was engineered into maize in order to improve the nutritive value. An intron was shown to be essential for the alpha-lactalbumin gene to become expressed.
Reference: S.K. Yang et al. (2002) Expression of a synthetic porcine a-lactalbumin gene in the kernels of transgenic maize. Transgenic Research 11: 11-20.
Soybean with additional maize protein to increase sulphur amino acids
The 15 kDa maize zein protein has been introduced into soybean to increase the sulphur amino acid content, in order to improve the nutritional value of soybean. Genetically modified soybean expressing the maize zein indeed contained higher levels of the sulphur amino acids methionine and cysteine. The authors (Dinkins et al.) conclude zein levels may be increased further by the use of an alternative promoter to drive the expression of the maize zein gene.
Reference: R.D. Dinkins et al. (2001) Increased sulfur amino acids in soybean plants
overexpressing the maize 15 kDa zein protein. In Vitro Cellular and Developmental Biology - Plant 37: 742-747
Cottonseed oil with increased monounsaturated fatty acids
Cotton was genetically engineered in a similar way as previously done with "high oleic acid soybean" by suppression of the delta-12-desaturase. Cottonseeds from the genetically engineered cotton contained increased levels of oleic acid, a monounsaturated fatty acid. High oleic acid oils may find their application as frying oils, being less prone to oxidation during frying than other common oils that are high in polyunsaturated fatty acids.
Reference: K.D. Chapman et al. (2001) Transgenic cotton plants with increased seed oleic acid content. Journal of the American Oil Chemists’ Society 78: 941-947
Soybean with anti-hypertensive peptide
A major protein (alpha-glycinin) of soybean has been mutated such that it contained an anti-hypertensive six-amino-acid peptide. This mutated protein was purified from experimental soybeans and was tested on hypertensive laboratory animals. The purified mutated protein was able to lower blood pressure in the hours following ingestion.
Reference: N. Matoba et al. (2001) Design and production of genetically modified soybean protein with anti-hypertensive activity by incorporating potent analogue of ovokinin(2-7). FEBS Letters 497: 50-54
Genetically modified soybean: inserted DNA characterised
With the use of PCR techniques, the "border DNA sequences" that flank the inserted gene in Roundup Ready soybeans have been determined. These soybeans have been on the market since 1996. An additional fragment of the inserted gene was found in one border region (at the 3’ end of the insert).
Reference: P. Windels et al. (2001) Characterisation of the Roundup Ready soybean insert. European Food Research and Technology 213: 107-112
Bt maize found to contain more lignin
More lignin was present in stems of maize plants that had been transformed with Bt genes (commercial lines) than in their non-Bt counterparts. The presence of lignin was analysed both chemically and microscopically. Maize plants had been grown in plant growth rooms and in the field.
Reference: D. Saxena and G. Stotzky (2001) Bt corn has a higher lignin content than non-Bt corn. American Journal of Botany 88: 1704-1706.
Uptake of DNA fragments from consumed plants by cows and chicken
Cows and chicken fed genetically modified, insect resistant maize were found to take up maize DNA fragments from digested maize material. No DNA fragments arising from the "foreign DNA" that had been inserted into the genetically modified maize could be detected in these animals, however.
Reference: R. Einspanier et al. (2001) The fate of forage plant DNA in farm animals: a collaborative case-study investigating cattle and chicken fed recombinant plant material. European Food Research and Technology 212: 129-134.
Review of feeding experiments with domestic animals fed genetically modified crops
Studies on domestic animals (such as chicken and cow) fed genetically modified crops (insect-resistant maize; herbicide-tolerant maize; herbicide-tolerant soybean) have been reviewed.Results of the reviewed studies include animal performance and composition of the genetically modified crops. The authors Clark and Ipharraguerre conclude that the feeding value of genetically modified crops is similar to that of their non-modified counterparts.
Reference: J.H. Clark and I.R. Ipharraguerre (2001) Livestock performance: feeding biotech crops. Journal of Dairy Science 84 (E. Suppl.): E9-E18.
Remote expression of RNA
Mutant messenger RNA (mRNA) was translocated through tomato plants and functionally active after translocation.
Reference: M. Kim et al. (2001) Developmental changes due to long-distance movement of a homeobox fusion transcript in tomato. Science 293: 287-289
Tomatoes expressing chalcone isomerase show increased contents of flavanoids (rutin and a kaempferol glycoside).
Reference: S.R. Muir et al. (2001) Overexpression of petunia chalcone isomerase in tomato results in fruit containing increased levels of flavonols. Nature Biotechnology 19: 470-474
High-yielding rice on poor soils
Rice transgenic for two phytosiderophores (iron binding compounds) from barley sustains on alkaline soils with low iron availability and delivers comparatively high yields.
Reference: M. Takahashi et al. (2001) Enhanced tolerance of rice to low iron availability in alkaline soils using barley nicotianamine aminotransferase genes. Nature Biotechnology 19: 466-469, 417
Transgenic pigs excreting less phosphate
Transgenic pigs excreting a foreign phytase enzyme, which is a common feed additive, into their salivary glands demonstrate better utilisation of dietary phosphate.
Reference: S.P. Golovan et al. (2001) Pigs expressing salivary phytase produce low-phosphorus manure. Nature Biotechnology 19: 741-745
The juvenile phase, i.e. the time between emergence and flowering & fruit formation, has been significantly shortened in citrus trees transgenic for either of two genes.
Reference: L. Pena et al. (2001) Constitutive expression of Arabidopsis LEAFY or APETALA1 genes in citrus reduces their generation time. Nature Biotechnology: 19 263-267
Mice were successfully immunised against rotavirus- and E. coli- antigens expressed in genetically modified potatoes.
Reference: J. Yu & W.H.R. Langridge (2001) A plant-based multicomponent vaccine protects mice from enteric diseases. Nature Biotechnology 19: 548-552
Rice transgenic for puroindolinone compounds produced softer rice kernels. In addition, flour production from these rice kernels yields more finer particles and less damage to starch.
Reference: K. Krishnamurty & M.J. Giroux (2001) Expression of wheat puroindoline genes in transgenic rice enhances grain softness. Nature Biotechnology 19: 162-166
Salt resistant tomato
Tomato plants transgenic for a Na+/H+ antiport were able to grow and develop fruits when grown in a model system on fluid containing 200 mM NaCl.
Reference: H.X. Zhang and E. Blumwald (2001) Transgenic salt-tolerant tomato plants accumulate salt in foliage but not in fruit. Nature Biotechnology 19: 765-768
Levels of the transgenic Bt toxin amounted up to 45% of soluble leaf protein.
Reference: B. de Cosa et al. (2001) Overexpression of the Bt cry2Aa2 operon in chloroplasts leads to formation of insecticidal crystals. Nature Biotechnology 19: 71-74
Mastitis-resistance may be conveyed to cows by genetic engineering with a mutant form of a bacterial cell wall degrading enzyme, as model experiments in mice show.
Reference: D.E. Kerr et al. (2001) Lysostaphin expression in mammary glands confers protection against staphylococcal infection in transgenic mice. Nature Biotechnology 19: 66-70