The FLAVR SAVR™ tomato (Lycopersicon esculentum) was developed through a specific genetic modification to exhibit decreased polygalacturonase (PG) activity. The novel variety was developed by insertion of an additional copy of the PG encoding gene in the “antisense” orientation, resulting in reduced translation of the endogenous PG messenger RNA (mRNA). The PG enzyme is the chief mechanism of pectin degradation in tomato fruit leading to fruit softening. The transgenic variety ripens normally but experiences less pectin breakdown and, therefore, has increased thickness and consistency that benefits all stages of harvesting and processing.<br>The FLAVR SAVR™ tomato was created by Agrobacterium-mediated transformation in which the<br>transfer-DNA (T-DNA) contained a copy of the tomato PG encoding gene in the antisense orientation. In addition, the T-DNA contained sequences encoding the enzyme neomycin phosphotransferase II (NPTII). The expression of NPTII activity was used as a selectable trait to screen transformed plants for the presence of the antisense-PG gene. Transcription of the antisense-PG gene did not result in the expression of any novel protein. There was no incorporation of translatable plasmid DNA sequences outside of the T-DNA region.<br>The mechanism of decreased PG activity in FLAVR SAVR™ tomato is likely linked to the hybridization of antisense and sense mRNA transcripts, resulting in a decreased amount of free positive sense mRNA available for protein translation. The measured level of PG activity in transgenic FLAVR SAVR™ tomato was found to be less than 1% of PG activity found in the unmodified parental line. The presence of NPTII protein has been judged to be insignificant with respect to any human health risk due to exposure. Alpha-tomatine is the principal naturally occurring glycoalkaloid in tomato, and the level of a-tomatine decreases as the fruit matures so that the amounts in vine-ripened red tomatoes are negligible. Solanine and chaconine, which are the main glycoalkaloids occurring in potato, have been found in tomato in lesser amounts. A comparison of the amounts of a-tomatine in transgenic and non-transgenic tomatoes did not reveal any statistically significant difference and the levels were within the normal range<br>reported for tomatoes. Other than reduced polygalacturonase activity, the disease, pest and other agronomic characteristics of the FLAVR SAVR™ tomato were comparable to unmodified varieties.