Leucine aminopeptidase A is a regulator of the wound and defense responses in tomato

When plants are wounded, either through mechanical wounding or through insect infestation, the ocatdecanoid pathway is activated; producing systemin, oligogalacturonic acid, C6 volatiles, and the oxylipins 12-OPDA and jasmonic acid (JA). These signals stimulate the accumulation of proteins and chemicals that will deter insect infestation. Leucine aminopeptidase A is a wound induced enzyme with an unknown function. LapA-silenced (LapA-SI) lines that do not accumulate LapA RNAs or protein upon wounding were used to investigate the role of LAP-A in tomato. LapA-SI lines have an impaired late (but not early) wound response and reduced defenses to Manduca sexta feeding. Exogenous jasmonic acid (JA) could not restore the wound response in LapA-SI plants, indicating that LAP-A acts downstream of the biosynthesis of JA, and is not regulated through COI1. LAP-A is necessary for a full wound response and modulates the wound response in tomato. LapA over-expressing (LapA-OX) lines were used to further investigate the role of LAP-A in the wound response. LapA-OX lines accumulated LapA RNAs and proteins in healthy plants. LAP-A was not sufficient to activate the wound response. After wounding, LapA-OX plants hyper-accumulated Pin gene transcripts (but not early wound-response gene RNAs). This response was quantitatively and temporally distinct from the wound response in wild type plants. LAP-A appeared to amplify the accumulation of Pin RNAs in the presence of other wound signals This hyper-accumulation of Pin RNAs was not reproducible through the application of exogenous JA however, indicating that it was wounding specific. LapA-OX plants had a greater resistance to feeding by Manduca sexta larvae. LAP-A represents the first aminopeptidase that has a regulatory function in plants, while its exact role is still being determined, LAP-A plays a critical role in facilitating the expression of wound response products, and deterring herbivory.