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Risk Assessment
Record information and status
Record ID
Date of creation
2010-09-20 07:32 UTC (german_bch@bvl.bund.de)
Date of last update
2020-07-16 14:10 UTC (german_bch@bvl.bund.de)
Date of publication
2020-07-21 07:03 UTC (nina.opitz@bmel.bund.de)

This document is also available in the following languages:
General Information
  • Germany
Title of risk assessment
6786-01-0145 (adv. 42010.0145); Summary of the risk assessment of a deliberate release (field trial) of genetically modified poplars (Populus x canescens) transformed with plasmid p70gshI, issued by the German Competent Authority
Date of the risk assessment
Competent National Authority(ies) responsible for the risk assessment
Federal Office of Consumer Protection and Food Safety
Mauerstrasse 39-42
Germany, 10117
Url:http://www.biosafety-bch.de (english language),BVL Homepage (English)
Methodology and points to consider
Potential adverse effects identified in the risk assessment
The execution of this field trial is not expected to have a negative impact on human or animal health, or on the environment.
Estimation of the overall risk
Adverse effects on human or animal health or on the environment are not expected.
Receiving environment(s) considered
2 field sites in Germany, details see German LMO/GMO location register ( https://apps2.bvl.bund.de/stareg_web/localeSwitch.do?language=en&page=/showflaechen.do?)
LMO detection and identification methods proposed
PCR-based method, construct-specific
Additional Information
Additional Information
These genetically modified grey poplars express the gshl gene from Escherichia coli which codes for a γ-glutamylcysteine synthetase. γ-glutamylcysteine synthase plays an important role in the synthesis of glutathione (glutamyl-cysteinyl-glycine, GSH) insofar as it specifically catalyses the ligation of glutamic acid and cysteine to form glutamylcysteine under energy consumption. Other γ-ECS substrates are not known. Glutathione is formed in a second step, in which glycine is bound to the dipeptide by glutathione synthetase. Increased levels of glutathione are synthesised in these plants compared with control plants.

Glutathione performs several functions in plant cells. As an antioxidant, it protects plant cells against oxidation, acts as a reserve for organic sulphur and as a precursor for phytochelatins [(γ-glutamylcysteine)n-glycine; n=2-11] it contributes to the detoxification of xenobiotics and heavy metals. This is brought about by the formation of stable complexes with metal ions from the thiol group of the cysteine residues of phytochelatins, which are pumped under ATP consumption into the plant cell vacuoles where they are stored.

To transform the grey poplar the start codon of the endogenous gshI gene from E. coli was modified from TTG to ATG in the p70gshl construct. This causes an amino acid exchange from leucine to methionine. Expression of the gshl gene takes place under the control of the 35S promoter from the cauliflower mosaic virus (CaMV) with a double enhancer region and the CaMV 35S termination signal. Southern blot analysis demonstrated that two copies of the gshl gene were transferred into the genome of the ggs11 transformant.

Results of studies on the ggs11 transformant showed that the transfer of the gshl gene leads to increased expression of active γ-ECS in the cytosol and that increased levels of glutathione are synthesised in these plants compared with control plants. In contrast, in comparison to the wild type there was no increase in either the total protein content of the examined leaves from the transgenic plant or in the level of glutathione reductase activity recorded. Phenotypic differences between the GM grey poplar and the wild type were not observed.

γ-glutamylcysteine synthetase (γ-ECS) is found in all plants. Therefore the enzyme is not expected to have toxic properties.

An increased production of glutathione is considered essential if the plant to perform its intended function, i.e. the improved uptake of heavy metals. The formation of phytochelatins necessary for this may alter the source-sink distribution of the individual components (in particular cysteine and glutamic acid). This process will be the focus of studies to be conducted within the scope of the deliberate release (field trial). This is not expected to have harmful effects on human health or the environment.

The ggs11 plants produce more glutathione in the stem and in old and young leaves than the non-transformed wild type. In the roots of both plant groups no differences in glutathione synthesis were found. Results of studies on absorption of cadmium from the soil solution revealed that in comparison to the non-transgenic control plants, only the young leaves of the ggs11 plants exhibited a significantly higher Cd content. In the roots, stem and old leaves, as well as in the whole plants, the Cd concentrations did not differ between the GM plants and the non-GM control plants. To date, it is not known to what extent the transgenic plants differ from non-transgenic grey poplars and other plants that grow in the area of the release site with regard to their capacity to absorb additional pollutants and to store these in different plant organs. This question is to be examined within the scope of the proposed deliberate release (field trial).

The modified grey poplar plants were selected using the nptII-gene product NPT. Hence the plants must be considered to be resistant against antibiotics like neomycin and kanamycin.

The genetically modified plants are not intended for use in the production of foodstuffs or animal feed.

Grey poplar has the capacity to form adventitious shoots (stolons, root suckers) from its roots. Any residual material with the potential to re-sprout shall be inactivated by applying herbicide. During the release period, the trial sites are to be monitored for the emergence of stolons. The fields are to be monitored and treated with herbicide for a period of two years after completion of the trials; any emerging root suckers are to be killed off with herbicides. During and after the trials, monitoring is to include a 15 m area surrounding the release sites. The possibility that the grey poplar root system might also grow beyond the area of the release site during the course of the trial and that suckers could develop from these roots is thus taken into account.

In studies and observations carried out to date on the morphological characteristics of the GM grey poplar plants in question, both under greenhouse conditions and within the framework of a currently ongoing field trial, the applicant reports that no differences between the transgenic and the non-transgenic plants were found. Evidence of increased vitality or fertility of the transgenic poplars which would promote the persistence or invasiveness of the GM plants has not been found. Root parts that may remain in the ground following trial completion and post-trial monitoring are not expected to result in the persistence of the GM plants. Therefore, the risk of the GM grey poplar persisting in the environment or establishing new plants in this manner is extremely low.

The genetic modification transferred to the plants basically confers a selective advantage under the conditions of heavy metal contamination expected at the release sites. However, taking into account the measures planned during the trial (trial duration, prevention of flowering) and following completion of the project (post-trial monitoring), the GM grey poplars are not expected to have the ability to establish on these sites.
For these reasons neither the establishment nor the uncontrolled persistence of these GM plants is to be expected.

Grey poplar is dioecious. The GM plants intended for release originate from the female grey poplar clone INRA 717 1-B4. Pollen formation and dispersal can thus be ruled out. The pollen of Populus species is dispersed by wind. However, if the trial plants were to reach the flowering stage, the possibility of in-crossing and the development of fruit on the GM grey poplars could not be excluded.

According to the applicant, the GM poplars for the proposed deliberate release have been propagated vegetatively since the summer of 2002. By the time they are to be planted out (spring 2003) they will have reached a stage of development that roughly corresponds to one-year-old trees. Generally speaking, grey poplars reach the generative stage after about 7 to 15 years; under conditions of stress it appears that flowering may occur earlier. The traits transferred give no reason to expect a significant reduction in the time taken for the transgenic plants to reach sexual maturity.

The applicant plans to conclude the trial after three years, i.e. before the generative stage has been reached. Furthermore, the applicant plans to monitor the trees for emerging flower buds prior to leaf development in the spring, and to remove any occurring flower buds before anthesis in order to prevent any sexual exchange with other plants in the environment. Corresponding measures are described in the regulations set down in provision II.6 of the decision on this notification.

Experience shows that in trees which flower prior to leaf development the formation of flower buds can be reliably identified before the flowers open. As a result, the pollen-mediated transfer of genetic information from other plants to the GM poplars is not expected to occur.

At the end of the trial, the GM grey poplars are to be removed from the soil and burned in an incinerator equipped with the appropriate filters, together with the leaves that have accumulated and been collected over the period of the deliberate release, except in the case that parts of these trees are needed for further analysis. The approval authority expects this to be done in an environmentally sound manner.

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