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A metabolite profiling study has been carried out on Arabidopsis thaliana (L.) Heynh. ecotype Wassilewskija and a series of transgenic lines of the ecotype transformed with a CHS (chalcone synthase) antisense construct. Compound identifications by LC/ MS and 1 H NMR are discussed. The glucosinolate composition in rosette leaves was shown to vary naturally within this ecotype. Relatively modest environmental changes had a strong effect on the wild type level of flavonoids and some sinapate esters but much less effect on the glucosinolates. Potentially a reduction in the level of flavonoids could be expected in the transgenic lines relative to the wild type. In practice the reductions achieved were highly variable both between lines and within a given line on different occasions when the plants were grown. Possible reasons for this variability are discussed with reference to current models of gene silencing. The metabolite profiles of the transgenic lines were examined for unintended effects of the modification. An apparently major effect on the glucosinolate composition was shown to result from an unusual genetic variation in the ecotype and not from the modification. The modification did produce a different but much more subtle change in the levels of certain glucosinolates.

Genetically modified plants must be approved before release in the European Union, and the approval is generally based upon a comparison of various characteristics between the transgenic plant and a conventional counterpart. As a case study, focusing on safety assessment of genetically modified plants, we here report the development and characterisation of six independently transformed ARABIDOPSIS THALIANA lines modified in the flavonoid biosynthesis. Analyses of integration events and comparative analysis for characterisation of the intended effects were performed by PCR, quantitative Real-time PCR, and High Performance Liquid Chromatography. Analysis by cDNA microarray was used as a non-targeted approach for the identification of potential unintended effects caused by the transformation. The results revealed that, although the transgenic lines possessed different types of integration events, no unintended effects were identified. However, we found that the majority of genes showing differential expression were identified as stress-related genes and that environmental conditions had a large impact on the expression of several genes, proteins, and metabolites. We suggest that the microarray approach has the potential to become a useful tool for screening of unintended effects, but state that it is crucial to have substantial information on the natural variation in traditional crops in order to be able to interpret "omics" data correctly within the framework of food safety assessment strategies of novel plant varieties, including genetically modified plant varieties.

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