TRANSGENIC PLANTS RESISTANT TO INSECTS

Proteinase inhibitors are secondary metabolites present in all plants and it seems that their major role is protection of plants against attacks of animals, insects and microorganisms. One of the family of proteinase inhibitors are squash inhibitors of serine proteinases purified from seeds belonging to genera Cucurbita, Cucumis and Momordica. Squash inhibitors consist of 29-32 amino acid residues and are considered to be the smallest inhibitors of the serine proteinases known. Because of shortness, genes for these inhibitors could be synthesised and modified at different ways. Modifications could lead to changes in inhibitor activity. Tobacco as a model plant was transformed with 12 different genes of squash inhibitors. Stable integration of transgenes in putative transgenic plants was determined by PCR analysis using genomic DNA and primers that anneal to promoter and terminator region. The first step of proteinase inhibitor gene expression in transgenic plants was revealed by RT-PCR analysis. In entomological tests where larvae were fed with leaves, influence of transgenic T0 plants, as well as non-transgenic control plants on retardation of larval growth of S. littoralis was examined. Results of entomological tests showed that it is possible to express squash proteinase inhibitors in plants at level that significantly reduces S. littoralis larval growth.