Biology in the Laboratory

Biotech Labs and Food

What is Starlink corn and Bt?

The Flavr Savr tomato, also called also known as CGN-89564-2, was developed in response to consumer complaints that tomatoes were either too rotten to eat when they arrived at the store or too green. Growers had found that they could treat green tomatoes in the warehouse with ethylene, a gas that causes the tomato skin to turn red—but the tomato itself stayed hard. In the late 1980s, researchers at the biotech company Calgene discovered that the enzyme polygalactouronase (PG) controlled rotting in tomatoes. The scientists reversed the DNA sequence of PG; the effect was that tomatoes turned red on the vine, yet the skin of the tomatoes remained tough enough to withstand the mechanical pickers. However, before the Flavr Savr tomato was introduced to the market in the mid-1990s, Calgene disclosed to the public how the tomato was bioengineered—thus causing a public protest that led to the worldwide movement against genetically modified organisms (GMOs).

Starlink was a bioengineered corn variety that was genetically modified to include a gene from the bacterium Bacillus thuringiensis (Bt), which produces a protein (called an endotoxin) that kills some types of insects. Bt endotoxin has been registered as a biopesticide in the United States since 1961, and the Bt endotoxin has been used by organic farmers for biological pest control. The endotoxins only become activated in the guts of susceptible insects. Because of the significant losses to corn crops caused by the European corn borer, scientists targeted the corn plant itself as a candidate for insertion of the Bt gene.


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