GM Free Cymru

Bt toxin has a detrimental effect on GM plant growth and development

GM-Free Cymru Comment:

This is a very significant new study from India. It shows that GM plants (in this case those manipulated to be toxic to certain insects) are severely damaged by the GM process. "This is a completely unexpected finding," said the editor of the journal of Bioscience. Hmmm -- not sure about that. It has been well known for many years that Bt toxins in GM plants lose their efficacy in the killing of pests (both targeted and otherwise) over time -- which presumably means that the plant is seeking to reject the toxic inserts put into it by Monsanto and other GM scientists. Sorry -- I meant "GM technologists." Also, if a plant is bombarded with alien material it is bound to be stressed -- and in those circumstances, why should anybody be surprised that there will be abnormalities and mutations, that yields will drop off, and that the plants reproductive functions will also be compromised? GM plants are supposed to be distinctive, uniform and stable in order to pass the DUS test -- that is supposed to be mandatory in order for any GM variety to obtain approval in Europe. Is there a single GM variety on the market capable of passing the DUS test as it should be properly conducted? I doubt it....... since approvals are always based on the developer's own assurances and upon the absurd concept of "substantial equivalence."

GM watch comment:

A new study shows that expression of the Bt insecticidal toxin (cry1Ac) gene in GM Bt tobacco and cotton has a detrimental effect on the growth and development of the plant. The plants that express high enough levels of the insecticidal toxin to control pests grow and develop less well and are more likely to have abnormalities. The plants that express low levels of the toxin (and therefore are unlikely to be able to control pests) grow and develop better and are less likely to have abnormalities. It seems that GM Bt insecticidal plants may have an unintended built-in self-destruct mechanism. --- --- "The expression of Bt endotoxin Cry1Ac has detrimental effect on the in vitro regeneration as well as in vivo growth and development of tobacco and cotton transgenics"

by Rawat, P., A. K. Singh, et al. (2011). J Biosci 36(2): 363–376.

ABSTRACT High levels of expression of the cry1Ac gene from Bacillus thuringiensis cannot be routinely achieved in transgenic plants despite modifications made in the gene to improve its expression. This has been attributed to the instability of the transcript in a few reports. In the present study, based on the genetic transformation of cotton and tobacco, we show that the expression of the Cry1Ac endotoxin has detrimental effects on both the in vitro and in vivo growth and development of transgenic plants. A number of experiments on developing transgenics in cotton with different versions of cry1Ac gene showed that the majority of the plants did not express any Cry1Ac protein. Based on Southern blot analysis, it was also observed that a substantial number of lines did not contain the cry1Ac gene cassette although they contained the marker gene nptII. More significantly, all the lines that showed appreciable levels of expression were found to be phenotypically abnormal. Experiments on transformation of tobacco with different constructs expressing the cry1Ac gene showed that in vitro regeneration was inhibited by the encoded protein. Further, out of a total of 145 independent events generated with the different cry1Ac gene constructs in tobacco, only 21 showed expression of the Cry1Ac protein, confirming observations made in cotton that regenerants that express high levels of the Cry1Ac protein are selected against during regeneration of transformed events. This problem was circumvented by targeting the Cry1Ac protein to the chloroplast, which also significantly improved the expression of the protein.


1. Gene alarm on GM crops The Telegraph (Calcutta, India) June 2 2011

Indian scientists have discovered that the genetic modification of plants with a gene already used in crops worldwide may severely damage the plants, a surprising finding that may stir a debate on current crop biotechnology science. The scientists at the University of Delhi have shown that inserting a bacterial gene that makes a protein named Cry1Ac into genomes of plants appears to cause developmental defects, growth retardation and sterility in the plants. Several experimental and commercial genetically-modified plants, including GM cotton cultivated in India and other countries, make the Cry1Ac protein which is toxic to some insects. The insects die when they try to eat parts of these GM crops. The Delhi scientists have now shown through laboratory experiments that modifying cotton or tobacco with Cry1Ac has a detrimental effect on these plants. Their results have appeared in the Journal of Bioscience published this month by the Indian Academy of Sciences. "This is a completely unexpected finding," said Durgadas Kasbekar, a senior biologist with the Centre for Cellular and Molecular Biology in Hyderabad who was not associated with the study, but is the editor of the Journal of Bioscience. "Until this point, if you asked someone in the plant biotechnology community what the Cry1Ac toxin does in plants, they would say it kills insects. No one has yet demonstrated harm to plants as this study has done," Kasbekar told The Telegraph. The Delhi researchers say such observations may have been overlooked in the past as most previous studies were aimed at finding plant varieties that can be genetically altered just enough so that they are suitable for cultivation. Independent studies have earlier shown that levels of Cry1Ac in some commercial GM cotton decline progressively over the life-cycle of the plant and are produced at such low levels in vulnerable parts of the crop that insects can continue to consume them. "We find a very strong correlation between the levels of Cry1Ac and abnormalities — higher the levels of Cry1Ac in the plants, the greater the damage," said Pradeep Burma, a plant geneticist at the University of Delhi South Campus, who led the study. Burma said these findings do not in any way suggest that GM crops are either unsafe for consumption or can cause damage to other crops or the environment. "But they reveal a previously unrecognised effect on GM plant development," Burma said. "It's a hurdle we need to overcome to improve insect-resistance in crops," he said. The researchers have themselves shown that if the plants are modified in such a way that the Cry1Ac is confined in their chloroplasts - the site of photosynthesis in plant cells — they do not show any developmental defects. "This could be a future strategy to protect plants from damage," Burma said. But scientists caution that the study describes observations and the mechanism of how the toxin harms host plants remains unclear. "We need to understand why the plants are being affected — and use that knowledge to make better plants," Kasbekar said. The Indian government had approved commercial cultivation of GM cotton containing Cry1Ac in 2002, and research groups have been trying to equip other plants with this protein. But a proposal to introduce GM brinjal with Cry1Ac has been stalled by the environment ministry amid concerns among sections of scientists and environmental activists about safety and environmental impact of edible GM crops. --- ---

2. BT gene in GM crops harmful for growth Deccan Chronicle June 3, 2011

A team of Indian scientists has found that genetic modification (GM) will have a detrimental effect on the growth and development of plants. This is the first time that scientists have found that the Bt gene will trigger major problems in plants like stunted growth and sterility. Thus far, studies have centred on the toxicity of the Bt gene to animals and human beings. There has been considerable interest and activity in genetically engineering insect-resistant crop plants using 'Cry genes' encoding insect toxins from the soil bacterium Bacillus thuringiensis (Bt). The proteins encoded by these genes are called Bt-toxins and are thought to specifically affect only certain insects and not other organisms or the plants themselves. However, the team from the laboratory of Dr Pradeep Burma in the Department of Genetics at the University of Delhi, South Campus, has found that expression of the Bt-toxin 'Cry1Ac' in cotton and tobacco is detrimental to the growth and development of those plants. The study was published in the June issue of Journal of Biosciences. "Many of the transgenic plants obtained showed developmental defects comprising abnormal growth (stunting) and/or sterility. These symptoms suggest that expression of Cry1Ac could be causing growth defects in plants," the team observed. Consistent with this explanation, the researchers found that a majority of transgenic plants had very low or undetectable levels of Cry1Ac, and that all plants having appreciable levels of Cry1Ac showed developmental abnormalities. This indicates a correlation between the levels of Cry1Ac expression and the developmental defects in the plants. Plants release defence-related molecules to fight the toxicity induced in them through Bt technology. Though studies have not been conducted to establish whether these defence-related molecules will cause harm to human beings when they are consumed, scientists here feel that the toxins released may also be detrimental to human and animal health.