Understanding the molecular and chemical basis of plant-insect communication.

Abstract

Plant defense signaling involves a complex network of interacting signals majorly regulated by phytohormones. A large number of studies have shown the critical role played by the phytohormones jasmonic acid (JA), salicylic acid (SA), ethylene (ET) and abscisic acid (ABA) in this However; all these studies have been majorly limited to the context of folivory (leaf eating herbivory) although there are many other interactions present in nature. One such interaction is frugivory (fruit herbivory) of eggplant: Solanum melongena (Solanaceae) by the specialist insect herbivore Leucinodes orbonalis Guenee [shoot and fruit borer (SFB), Lepidoptera: Pyrallidae]. Eggplant, being one of the most important vegetable crops in Asia faces major threat from SFB, with infestation potential to the extent of 70 to 93 percent. None of the pest management strategies employed in field offered resistance to SFB to an adequate level. The chemistry of plant-insect interaction in this case is poorly understood. In this study, we report the involvement of two phytohormones ABA and ET in eggplant fruit response towards SFB attack. Our results show the increased metabolite level of ABA and increased transcript level accumulation of identified eggplant putative ET biosynthetic genes in response to SFB feeding. Our findings report that two major classes of defense metabolites of Solanaceae family, steroidal alkaloids and phenolics abundantly present in eggplant fruit did not respond to frugivory. Future studies focusing on the role played by these phytohormones and their downstream targets can provide new insights about this crop-pest interaction that can be exploited in pest management strategies.