Extensive transcriptome and microarray studies are yielding a propensity of new knowledge about the classes of genes whose expression is modulated by plant pest interactions. PI genes have often been found among the gene classes coupled to the defense response. In our study of the interaction of the sugar beet root maggot with the sugar beet root, a gene that encodes a serine PI was found to be up-regulated in a sugar beet line with moderate MEDChem Express 1805787-93-2 resistance to the maggot. Since serine proteases comprise the major digestive enzymes in the root maggot midguts, these findings suggested that the BvSTI gene may be part of the overall resistance mechanism that protects the plant from insect attack. To investigate the potential function of the BvSTI PI gene in insect resistance, the gene was reconstructed for over-expression in transgenic plants. We report on the expression of the sugar beet BvSTI transgene in N. benthamiana plants and bioassay of the transgenic plants for insect resistance to five Lepidoptera insect pests. Plants have an assortment of defensive genes whose products harm insects and pathogens. Among the mechanisms of plant defense are genes that in response to wounding lead to the expression of proteinase inhibitors that disrupt protein digestion in insect midguts. Over-expression of heterologous PI genes in crop plants has resulted in enhanced resistance to a wide spectrum of insect pests. However, the ongoing challenge of the PI based insect control strategy is the need to discover and characterize new and novel PIs to address the inherent and Tonabersat induced complexity of the insect gut proteases. PIs such as those derived from non-host plants to which the targeted insect has had minimal or no prior exposure can generally be most useful for enhancing insect resistance in engineered plants. In a study of sugar beet root defense responses, a single serine PI gene was identified among the more than 150 sugar beet genes whose expression was found to be modulated by a dipteran pest of sugar beet, the root maggot. Expression of the BvSTI gene was determined to be up-regulated by mechanical-and insect-wounding in sugar beet lines used in breeding for root maggot resistance. The observed lack or reduced accumulation and activity of BvSTI PI in tissues of susceptible and less resistant lines emphasized the potentially important role of the BvSTI PI in insect pest defense mechanisms. In this study, the prospect of over-expressing the sugar beet BvSTI gene for control of lepidopteran insect pests in genetically modified N.