Plant proteinase inhibitors: a defensive response against insects. (Review)

Plants protect themselves against pests using their wide chemical defense arsenal. Among several defense proteins, proteinase inhibitors appear to be an important group. Proteinase inhibitors are widely present in plants and they are often found in storage organs. They are known to be inducible in plants by injuries, such as insect damage. Because these proteins inhibit digestive enzymes of insect larvae and microbial proteases, they may be considered as mechanisms to improve the plant defense against pests. In recent years, growing research on plant proteinase inhibitors has confirmed their important role in plant defense, although several aspects are still controversial. Although many plants have related proteinase inhibitors, which have been shown to affect metabolism and/or development of different insects, these plants do not seem to share a common inhibitor induction mechanism. This is an emerging field and much work is yet to be done.