Leucine Aminopeptidase: A Regulator of the Late Branch of Wound Signaling

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This proposal focuses on understanding the tomato leucyl aminopeptidase A (LapA). LAP controls tomato defenses after wounding and insect feeding. When LAP protein is reduced in transgenic LapA-SI plants, the proteins and chemicals that antagonize insect growth are produced at lower levels. LapA-SI plants incur more damage and tobacco hornworms are larger relative to insects from wild-type plants. In addition, on plants that make excessive amounts of LAP-A protein (LapA-OX), caterpillars consume less foliage and larval masses are reduced. The LapA-OX plants provide an important and new mechanism of insect resistance, since plant stature and fertility are not impaired. Understanding how LAP-A controls tomato defenses will be an important addition to our general knowledge of gene regulation in plants. Goal 1 is to determine the susceptibility or resistance of LapA-SI and LapA-OX plants to insects that use different modes of feeding. If LapA-OX plants provide resistance to many insect species, an important and new mechanism to protect plants from insect pests will have been discovered. Goal 2 is to use genetic, biochemical and plant transformation technologies to determine if the peptidase activity of LAP-A is essential for its role in controlling defenses against insects. This is important since LAPs from other organisms have multiple functions. Finally, Goal 3 is to determine the cellular process that is regulated by LAP-A. A new model that links the many signals that influence wounding in tomato and LAP-A is proposed. This model will be rigorously tested using molecular, biochemical and transgenic plant strategies. By supporting or refuting this model, these experiments will aide in defining the complex and largely unexplored defense network that plants employ against insects. These studies should result in new strategies for engineering an environmentally safe resistance to insects into crops and horticultural plants, benefiting agriculture and society at large. The proposed experiments range from whole organism studies to molecular responses and spans the fields of plant biology and entomology. This research program will provide a unique, interdisciplinary training environment for a graduate and undergraduate students and a postdoctoral fellow.