Complex sentence: Bt corn is a variant of maize that has been genetically altered to express the bacterial Bt protein, which is poisonous to certain insect pests and is widely used in organic gardening.
Split into simpler sentences: Bt corn is a variant of maize that has been genetically altered to express one or more proteins from the bacteria, Bt. The protein is poisonous to certain insect pests and is widely used in organic gardening.