Plant essential oils induce expression of heat shock proteins and antioxidant enzyme activity in carob moth, Ectomyelois ceratoniae (Lepidoptera: Pyralidae)

Abstract

Rising concerns about the negative eff ects of chemical compounds in pest control have made it increasingly necessary to fi nd new environmentally friendly compounds to combat insect pests. In recent years, the use of plant derivatives, such as, essential oils have proved very promising. Despite the many studies on essential oils, there are very few studies on the eff ect of these oils on induction of Heat shock proteins (HSPs) and antioxidant enzymes. Therefore, it was hypothesized that the exposure of insects to essential oils induce stress, which it is likely induces the production of heat shock proteins and antioxidant enzymes. Thus, Ectomyelois ceratoniae Clark (Lepidoptera: Pyralidae) was used as a model insect to study the lethal and sublethal eff ect of the fumigant toxicity of the essential oils extracted from the plants Thymus daenensis Celak and Satureja khuzistanica Jamzad. Gas Chromatography/Mass Spectrometry indicated that thymol and carvacrol were the major component of T. daenensis and S. khuzistanica extracts, respectively. Exposing E. ceratoniae to sublethal doses of the essential oils (LC30) and using RT-qPCR indicated that the expression levels of HSP70 and HSP90 were signifi cantly increased. Activities of antioxidant enzymes including SOD, CA, POX, GST and the concentration of MDA increased following exposure to sublethal doses of both essential oils. These fi ndings clearly show that in addition to the reported eff ects of essential oils, oxidative stress and induction of free radical production could be another mode of the action of essential oils on insects.