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Engineering Proteinase Inihibitor Genes For Plant Defense Against Predators, Clarence A. Ryan, Thomas Moloshok, Gregory Pearce, Gynhueng An, Robert W. Thornburg, Gerald Hall, Russell Johnson, Edward E. Farmer, Curtis Palm

Journal of the Iowa Academy of Science: JIAS

Small proteinaceous inhibitors (Mr<20,000) of the digestive serine proteinases of animals and microorganisms are found as moderately abundant proteins in storage organs and leaves of many plant genera. The proteins are powerful inhibitors of the digestive enzymes of plant predators and therefore are considered to be part of the array of defensive chemicals of plants. Proteinase inhibitor genes show excellent promise, using DNA technology, to manipulate plant genomes to express these biologically active proteins in order to improve natural defense systems. Members of two unrelated families of serine proteinase inhibitors found in tomato and potato plants, called Inhibitor I (monomer Mr 8000) and Inhibitor II (monomer Mr 12,300), are under both environmental and developmental regulation in different tissues of the plants. Genes coding for wound-inducible Inhibitors I and II have been isolated from both tomato and potato genomes and characterized. Tobacco plants have been transformed with the chimeric genes containing wound-inducible promoters fused with the reporter gene, chloramphenicol acetyl transferase, to assess promoter function and signal transmission. Transacting factors that regulate their expression in response to wounding are also being identified and purified. Intact genes are being employed to transform agriculturally important crop plants to determine their potential usefulness to enhance defensive capabilities of plants against herbivores and pathogens.