EXCERPT: Although such crops are claimed to be thoroughly tested before commercialisation and to be 'substantially equivalent' to non-GM varieties, the difference in lignin content reported here has only been discovered nearly a decade after commercialisation.
Bt Maize Has High Levels Of Lignin
Way back in November 1999 New Scientist reported that "Researchers in the US have found that Monsanto's herbicide-resistant soya beans are cracking up in the heat. When grown in hot climates, genetic alterations to the plant seem to cause the stems to split open causing crop losses of up to 40 per cent.... [Bill Vencill of the University of Georgia] suspects that the phenomenon is the result of changes in plant physiology caused by the addition of genes making the beans resistant to glyphosate, the herbicide marketed as Roundup by Monsanto. Plants carrying these genetic alterations have been shown to produce up to 20 per cent more lignin, the tough, woody form of cellulose."
Now new research has found that increased production of lignin also occurs in the stems of Bt GM maize plants, even though they incorporate a different genetic modification to Roundup Ready soya (see below - Journal of Environmental Quality 34:1508-1518 (2005)).
Although such crops are claimed to be thoroughly tested before commercialisation and to be 'substantially equivalent' to non-GM varieties, the difference in lignin content reported here has only been discovered nearly a decade after commercialisation.
The study states that "Transformation of crops, including maize (Zea mays L.), with the cry1Ab gene from Bacillus thuringiensis to combat lepidopteran pests results in pleiotropic effects regarding lignin biosynthesis...... The stems of the transgenic lines had higher concentrations of total lignin than the respective isogenic lines: Valmont T/Prelude by 18% and Novelis T/Nobilis by 28%." (Pleiotopy = multiple effects of a single gene which affects more than one phenotypic character - Henderson's Dictionary of Biological Terms).
Roundup Ready soya and Bt maize account for the majority of the GM acreage grown across the world. The implications of these unintended effects from genetic modification may become increasingly significant as global warming intensifies.
Tearing Down Biotech's 'Berlin Wall'
The Acceptable Face Of Ag-biotech
Published online 9 August 2005
Published in J Environ Qual 34:1508-1518 (2005)
© 2005 American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America
677 S. Segoe Rd., Madison, WI 53711 USA
Ecological Risk Assessment
Molecular Composition of Leaves and Stems of Genetically Modified Bt and Near-Isogenic Non-Bt MaizeCharacterization of Lignin Patterns
Juergen Poerschmanna,*, Achim Gathmannb, Juergen Augustinc, Uwe Langera and Tadeusz Góreckid
a UFZ-Center for Environmental Research Leipzig-Halle Ltd., D-04318 Leipzig, Germany
b RWTH Aachen, Institute of Environmental Research (Biology V), Chair of Ecology, Ecotoxicology, Ecochemistry, D-52076 Aachen, Germany
c Leibniz-Center for Agricultural Landscape and Land Use Research, D-15374 Muncheberg, Germany
d Department of Chemistry, University of Waterloo, Waterloo, ON, N2L 3G1 Canada
* Corresponding author ([email protected])
Received for publication February 25, 2005. Transformation of crops, including maize (Zea mays L.), with the cry1Ab gene from Bacillus thuringiensis to combat lepidopteran pests results in pleiotropic effects regarding lignin biosynthesis. Lignin patterns in stems and leaves of two genetically modified Bt-maize varieties (Novelis T and Valmont T) were studied along with their non-Bt near-isolines (Nobilis and Prelude, respectively). Molecular-level based thermochemolysis using tetramethylammonium hydroxide (TMAH) in combination with gas chromatographymass spectrometry (GCMS) was used to quantitate the total lignin contents and to identify monomeric lignin subunits including p-hydroxyphenyl (P), guaiacyl (G), and syringyl (S) moieties. The results were supplemented and confirmed by cupric oxide oxidation. The stems of the transgenic lines had higher concentrations of total lignin than the respective isogenic lines: Valmont T/Prelude by 18% and Novelis T/Nobilis by 28%. In contrast, differences in the total lignin concentration of leaves between the transgenic and the respective near-isogenic lines were marginal. There were significant modifications in the ratio of p-hydroxyphenyl/guaiacyl/syringyl molecular marker units of stem lignin between transgenic and isogenic lines. The guaiacyl units (in particular the G18 marker) accounted chiefly for the higher total lignin contents in the transgenic lines. The leaf lignin patterns did not show significant differences in molecular markers between isogenic and transgenic lines. TMAH-induced thermochemolysisconducted in both the on-line and off-line modesprovided detailed information on the molecular composition of lignin, thus proving superior to the established "wet chemistry" methods of lignin determination.
Abbreviations: amu, atomic mass unit FFAP, free fatty acid phase G, guaiacyl unit GCMS, gas chromatographymass spectrometry P, p-hydroxyphenyl unit RSD, relative standard deviation • S, syringyl unit • TMAH, tetramethylammonium hydroxide
Go to a Print friendly Page
Email this Article to a Friend
Back to the Archive