Susceptibility Of Beet Worm, Spodoptera Exigua, To Some Insect Growth Regulators And CDNA Cloning Of Its Ecdysone Receptor Complex

The beet armyworm, Spodoptera exigua(Hb(u|¨)ner),is a polyphagous noctuid of worldwide importance that feeds on various agricultural crops, including vegetable, cotton and onamental. The heavy dependence on insecticide for control of this pest has resulted in the emergence of resistance to a variety of insecticides. Insect growth regulators(IGRs) including tebufenozide and chitin inhibitors are the major insecticides used to control Spodoptera exigua in the fields. They have selective toxicity towards different pests, and have no adverse effects on mammals, birds, fishes and other vertebtrates, as well as various beneficial insects. In order to maintain long effective controlling, we must pay more attention to sensitivity of these insecticides to beet armyworm.Ecdysteroids cause a molt by combining with the ecdysone receptor (EcR) and the ultraspiracle protein (USP) heterodimer to initiate a molting cascade including expression of transcription factors, which in turn regulate tissue-specific genes involved in molting and metamorphosis. Tebufenozide is a noval synthetic non-steroidal ecdysteroid agonist, which manifests its toxic effects through interaction with heterodimer of ecdysteroid receptor and ultraspiracle protein. Insect larvae treated with tebufenozide undergo premature lethal moulting. Chitin inhibitors can prevent chitin from synthesizing and tansporting and result in pest death.The availability of cDNA clones for EcR and USP from several insect species has opened up possibilities for the development of high throughput EcR/USP based screening assays. This can be done in several ways, and depending on the screening strategy. EcR/USP proteins can be produced by in vitro transcription and translation of cDNAs in bacteria, yeast and insect cells. Either crude or purified proteins can be used in displacement assays using labeled ecdysteroid or ponasterone A. The purpose of clonging EcR and USP...