have demonstrated that LAP-A has a regulatory role in the immune response in tomato. Background on plant immune response In order to survive, plants must be able to respond to many biotic and abiotic stresses, including pathogen attack, piercing/sucking insects, herbivory, and mechanical wounding. These stresses activate specialized signal transduction pathways, which are specific to the stressor and the amount of tissue damage inflicted. Similar to mechanical wounding, chewing insects, such as the tobacco hornworm (Manduca sexta, one of the major pests of tomato), cause extensive tissue damage activating the jasmonic acid (JA)-mediated response (Walling 2000). This JA-mediated response revolves around the octadecanoid pathway, which is responsible for the synthesis of JA and several other potent signaling molecules, and ends in the regulation of two sets of genes whose expression changes over time. The early genes amplify the wounding signal and can be detected 30 minutes to 2 hours after damage (Ryan 2000). Late gene expression can be seen 4–24 hours after wounding. Products of late-response genes act as deterrents to chewing-insect feeding, often by decreasing the nutritional value of the food ingested or interfering with insect gut function (Walling 2000). For example, serine proteinase inhibitors (Pins) interfere with digestive proteases in the insect gut and polyphenol oxidases (PPO) act to decrease the nutritive value of plant leaves after ingestion by herbivores (Johnson et al. 1989; Ryan 2000; Orozco-Cardenas 2001). Please see the Picture 3 for a summary of the wound response in tomato. The plant response in this octadecanoid pathway is similar to mammalian prostaglandin and leukotriene pathways (Ref Walling 2000). This particular pathway is inhibited by salicylic acid. Octadecanoid pathway (LAP-A), a product of the octadecanoid pathway in some solanaceous plants, has been shown by Fowler et al. to have a regulatory role in the late wound response of tomato. Experiments were conducted using three genotypes of tomato plants: wildtype (WT), (LapA-SI) plants that were silenced for LAP-A, and LapA-OX that constitutively expressed LAP-A. Late-gene expression was inhibited in wounded LapA-SI plants, and the LapA-SI plants were also more susceptible to tobacco hornworm feeding, relative to wildtype (WT) plants. In comparison, the wounded LapA-OX leaves exhibited heightened levels of late gene RNA accumulation, an increased resistance to herbivory, and extended expression of late wound-response genes. These data suggest that LAP-A functions in regulating both the intensity and the persistence of the late wound response. However, unwounded LapA-OX did