The Role of Leucine Aminopeptidase in Plant Defense

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9318260 Walling Aminopeptidases are exopeptidases that hydrolyze the N-terminal amino acid from peptides and proteins. In animals, aminopeptidases have an important role in nutrition and modulation of the activities of gut and brain peptide hormones by converting them to active or inactive forms. In addition, these exopeptidases may have a role in modulating half-lives of proteins in vivo. Surprisingly; little is known about aminopeptidase activity during plant development. Although aminopeptidases are known to be induced after germination and during senescence, the expression of these genes during the plant life cycle or in response to biotic or abiotic stress has not been characterized. Dr. Walling has isolated and characterized a leucine aminopeptidase (lap) cDNA clone from Lycopersicon exculentum (tomato). Leucine aminopeptidase mRNAs are induced to high levels after mechanical injury, insect feeding, and Pseudomonas syringae pv. tomato infection. LAP proteins and activity are also induced after wounding. Two wound-induced lap genes are present in the tomato. The proposed research is a multi-faceted approach to understanding the expression, localization, and function of LAPs during the plant-defense response. Furthermore, these studies will be exteded to gain a comprehensive understanding of lap gene expression throughout plant development and in response to abiotic stress. Only recently, have plant leucine aminopeptidase genes been isolated, and few directed efforts have been made to understand their expression and impact on the plant responses to the environment and to developmental cues. Elucidation of the role of LAPs during the plant defense reaction and during development will enhance our understanding of the mechanisms that favor optimal growth and development. These factors will directly impact on optimal crop productivity and potentially yield insights for strategies to enhance a plant's endogenous protection mechanisms. ***