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).