Service Communautaire d'Information sur la Recherche et le Développement - CORDIS

ESTIM: engineering stress tolerance in maize

The engineering of stress tolerance in maize is based on the modulation of expression of genes encoding superoxide radical and hydrogen peroxide scavenging enzymes. To this end, gene products targeted to the chloroplasts are designed and introduced in maize. Genes of interest within this project are superoxide dismutases (SOD) and genes coding for enzymes from the ascorbate-glutathione cycle. Transformed maize containing either SOD or a hydrogen peroxide scavenging enzyme has been obtained. The procedure followed for transformation is based on co-transferring two independent plasmid vectors carrying the selectable marker gene and the chimeric genes of interest, respectively. As selectable marker gene, the CaMV35S-bar gene construct was used. The bar gene codes for phosphinothricin acetyl transferase that confers resistance to the herbicidal compound phosphinothricin. Several hundred primary transformants have been obtained of which, so far, 11 have been shown to have acceptable expression level. Scavenging enzymes have been analysed in nontransformed maize and expression levels in the primary transformants have been determined. Transformed maize has been obtained and molecular analysis of the primary transformants has been carried out. Rapid screen assay for physiological analysis has been established. The methyl viologen (MV)-assay has proven to be useful for the detection of differences in oxygen radical scavenging capacity between transgenic and non-transgenic plants. The assay can also be applied in maize.

Transgenic tobacco plants were used to facilitate the screening for gene constructs of potential interest. This has become especially relevant in light of the poor expression levels which have been obtained with the initial gene constructs. The expression levels of the transgenes remained below expectations. It was therefore decided to evaluate new gene constructs first in tobacco and only after that in maize. It is anticipated that this strategy will improve the changes for identifying the best working gene constructs.


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