An enzyme (e.g., present in tomatoes) that starts the breakdown (softening) of the fruit tissue. Recent advances make it possible to significantly delay the softening (i.e., spoilage) process by reducing the production of polygalacturonase through genetic engineering of the plant. In 1 986, William Hiatt of the American company Calgene discovered the gene for polygalacturonase, which led to that company commercializing a tomato variety that had been genetically engineered to reduce production of polygalacturonase in that variety’s tomatoes (in 1994).