FLAVR-SAVR

Flavr-Savr is the first commercially grown genetically modified tomato licensed for human consumption. It was developed by a California based company, Calgene in 1992 and sent to FDA for approval, on May 17, 1994 FDA completed its evaluation and concluding that the tomato is safe as the conventional one.

It was developed by a technique known as Antisense RNA-technology, plants outer surface is generally made up of carbohydrate polymer like pectin, lignin, cellulose which confirms the texture and firmness. During the time of ripening tomato develops a enzyme knows as Polygalactourodase and the concentration of the enzyme increases in the cell as the plant gradually ripe. this enzyme is mainly responsible for softening of the tomato, it digest the cell wall pectin which is cause of destruction of cell wall firmness, so tomatoes become more and more soften as the concentration of polygalactourodase increase and more and more susceptible to different fungal attack.
In this process the mRNA which is responsible for coding this enzyme is been locked in the nucleus with the help of Antisense-RNA, and which ultimate get degraded by RNase-H like enzyme. so reducing the number of enzyme coding mRNA in the cell reduces the concentration of enzyme and giving a extra few days to their live and making you worriless, you can use the tomato without being in hurry in your kitchen.
But the tomato didn’t last long in the market, its production ceased in 1997, and the mounting cost prevents the company from making profits.
there is good flash video on this you can visit - agbiosafety.unl.edu/flash/antisense.swf