We report the activity concentrations calculated from the assay that measured

plant proteinase inhibitors that are similarly characterized by their specificity toward proteases. PIs are considered attractive tools for crop improvement because their significant protective role in natural defense mechanisms has been well-documented. MK-8245 Defensive capacities of plant PIs rely on inhibition of the insect��s digestive proteases thus limiting the availability of amino acids necessary for normal insect growth and development. Transfer of PI genes to plants is a widely accepted technique for engineering enhanced levels of insect tolerance in plants. It has been conclusively demonstrated that over-expression of heterologous PI genes significantly reduced or inhibited larval growth and feeding on transgenic plants. The inhibition has been shown to be quite effective as demonstrated with bitter gourd PIs where more than 80% of Helicoverpa armigera serine proteases were inhibited by feeding on the transgenic PI plants. Expression of rice cysteine PI genes, oryzacystatin I and II, was shown to increase resistance to several coleopteran pests, as well as nematodes, that commonly use cysteine proteases for protein digestion. In addition to insects, sweet potato and taro PI genes were shown to control microbial pathogens in tobacco. In a reciprocal experiment where PI gene expression was suppressed in transgenic potato, an increase in larval weights of Colorado potato beetle and beet armyworm was reported. One of the major challenges of the PI based insect control strategy has been the management of the inherent and induced 160807-49-8 complexity of the insect gut proteases. Since non-targeted proteases often can compensate for the blocked proteases, several approaches may be needed to combat this problem. One relatively recent approach was shown to be effective when tobacco and potato inhibitors of the same class were expressed simultaneously in the transgenic plant. On the other hand, expression in tomato of two different classes of potato PI genes was shown effective for control of both a lepidopteran and a dipteran insect. The potential to control more than one pest by gene stacking and for targeting nematodes and microbial pathogens makes the PI approach highly desirable for crop improvement. Clearly, however, the continued success of the PI based applicati