Characteristics of plant proteinase inhibitors and their applications in combating phytophagous insects

Plant proteinase inhibitors (PIs), which play a potent defensive role against predators and pathogens, are natural, defense-related proteins often present in seeds and induced in certain plant tissues by herbivory or wounding. This review describes the main classes of proteinase inhibitors, the distribution and localization, general properties, the main functions, and commercial applications of plant PIs. This paper also introduces the proteinase inhibitor IIs (PIN 2) and its molecular biology, including transgenic plants expressing proteinase inhibitors against insect, pests, and pathogens, esp. in lettuce (Lactuca sativa L.) and Chinese flowering cabbage (Brassica campestris ssp. parachinensis), which are widely cultivated or distributed in Southeast Asia, especially in South China, including Hong Kong. The morphorlogical and molecular characteristics of PIN 2-rich American black nightshade (Solanum americanum Mill.) was described. In addition, prospects for the application of plant PIs are also discussed.