Transgenes in plants: protection against viruses and insects

Protective transgenes introduced into plants can be classified as directed against insects, fungi, bacteria or viruses. Mechanisms by which they protect plants in some cases are relatively simple and understood while in most cases they present only the field of rapidly progressing investigations. A brief review of the recent concepts of the resistance induced in plants against viruses by virus-derived transgenes is presented with emphasising the RNA mediated resistance. The RNA mediated resistance seems to operate in Nicotiana benthamiana plants transformed in our laboratory with cDNA of the PPV CP gene: both translatable and untranslatable versions of the cDNA made the transformed plants resistant against PPV. The resistant plants contained more than one copy of the transgene. To protect against insects plants were in our laboratory transformed with potato proteinase inhibitor II gene (PPI-II). The PPI-II gene expressed in model plants inhibited trypsin activity to an expected level.