Spider venom contains a mixture of peptide toxins, some able to kill insects specifically to
those considered as important pest. In this study, a peptide toxin produced by the Macrothele
gigas spider, Magi 6, was cloned and expressed in tobacco plants, as this toxin has
been shown to constitute an effective insecticide. For this purpose, a genetic construction
for the cDNA that codifies for Magi 6 was subcloned in a plant expression vector using the
35S promoter and the 50
-end leader from tobacco mosaic virus, in order to transform
tobacco leaf disks. The resulting plants demonstrated the presence of Magi 6 gene in the
tobacco genome using PCR, and transcription of the cDNA was verified by means of RTPCR.
The expression of the Magi 6 peptide in tobacco was demonstrated by Western blot,
which exhibited the expected size, thus suggesting a correct processing of the signal
peptide. No morphological alterations in the different transgenic lines were observed, nor
any change in plant growth. Subsequently, experiments were carried out challenging
detached leaves or whole plants with the herbivorous insect Spodoptera frugiperda. The
bioassays indicated that the transgenic lines were significantly more resistant than the
wild type plants. This work demonstrated that the expression of Magi 6 peptide in
transgenic plants conferred resistance to insect attack and opens the possibility of
employing this peptide to improve the resistance of diverse plants.