Submitted to: Journal of Chemical Ecology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/14/2007
Publication Date: 4/1/2007
Citation: Lawrence, S.D., Novak, N.G., Blackburn, M.B. 2007. Inhibition of proteinase inhibitor transcripts by leptinotarsa decemlineata regurgitant in lycopersicon esculentum. Journal of Chemical Ecology 33:1041-1048. Interpretive Summary: Colorado potato beetle costs hundreds of millions of dollars for pesticide control and yield loss each year in the United States. Understanding the natural defenses of the plant to this insect pest will allow scientists to know which genes should be manipulated to produce a plant that is better able to mount a defensive response to insect attack. Plants respond by mounting a defense to the actual mechanical damage, but they also respond to chemicals produced by the insect. We have begun the characterization of one of these chemicals, which is probably a protein that inhibits two proteins in the plant that are defensive to Colorado potato beetle. The insect protein may have evolved to counteract the plant defenses. This work increases our understanding of the specific plant/pest interaction and suggests that another control system may be necessary for these defense proteins in the plant to evade the Colorado potato beetle's attack. This research will be of interest to scientists studying plant resistance to pests.
Technical Abstract: One mechanism by which plants defend themselves against insect herbivores is the production of plant proteinase inhibitors, which can inhibit digestion in the midgut, thus affecting growth and survival. In this work, the effect of Colorado potato beetle (CPB) (Leptinotarsa decemilineata (Say) regurgitant on Lycopersicon esculentum defenses is investigated. When regurgitant from 4th instar CPB larvae was applied to wounded tomato leaves, the wound-induced transcripts for the proteinase inhibitors pin1 and pin2 were reduced. Boiling the regurgitant abolished its ability to reduce the pin transcripts. Ultrafiltration of the regurgitant demonstrated that it contained a component between 10,000 and 30,000 MW that inhibited wound-induced pin1 and pin2 expression, suggesting that it may be a protein. This may represent a mechanism that the CPB has evolved to elude the plant's induced response to infestation.