Comparative Study On Effects Of Sublethal Doses Indoxacarb On Juvenile Hormone And JHE Gene MRNA Expression Level Of Nilaparvata Lugens Stal (Hemiptera:Delphacidae) And Chilo Suppressalis (Walker) (Lepidoptera:Crambidae)

Both the rice stem borer, Chilo suppressalis (Walker)(Lepidoptera:Crambidae) and the brown planthopper, Nilaparvata lugens (Stal) (Hemiptera:Delphacidae) are important rice pests. In recent years, the new pyrazoline-type insectide indoxacarb was widely used to control Lepidopterous pests of rice, such as stem borer Chilo suppressalis, yellow rice borer Tryporyza incertulas and rice leaffolder Cnaphalocrocis medinalis Guenee. The present studies on physiological and biochemical changes in brown planthopper had shown that indoxacarb inhibits BPH reproductive. The fecundity of insects is mainly regulated by the synthesis of vitellin and vitellogenin, and vitellogenin synthesis is regulated by JH. JHE, a member of the carboxylesterase family, hydrolyzes JH into biologically inactive JH acid. In this study, we integrated the analysis of changes in JH III titer and JHE mRNA levels both in indoxacarb treated N. lugens adult females and Chilo suppressalis larve. The comparative analysis of effects of sublethal doses of indoxacarb on target and non-target insect pests reproductive in the same environment had significant guidance for integrated pest management, control efficacy evaluation and reasonable use of indoxacarb.1. Effects of Sublethal doses of indoxacarb on juvenile hormone and Nljhe mRNA expression level of Nilaparvata lugens Stal (Hemiptera: Delphacidae) adult femalesAll of the tested concentrations of indoxacarb caused a significant decrease in JH Ⅲ titer of N. lugens adult females both before and after mating, and JH Ⅲ titer decreased with the increasing of insecticide concentration. There was a significant negative correlation between JH Ⅲ titer and the concentrations of indoxacarb. JH Ⅲ titer decreased by 32.2%,31.7% and 44.5% at 1,3,5 days before mating compared with the untreated controls, and 42.8%,52.3% and 46.4% at 1,3,5 days after mating, respectively after indoxacarb treatments. JH Ⅲ titer in N. lugens adult females after mating was higher than that of before mating.The expression of Nljhe mRNA of N. lugens adult females both before and after mating was linear positively related to indoxacarb concentration, which was increased with the increase of indoxacarb concentration, especially before and after mating 3d. Nljhe mRNA average expression levels were 4.8,5.0,4.4 and were 6.5,7.6,5.3 times the control levels before and after mating at 1,3 and 5d, respectively. Indoxacarb significantly induced female adults of the brown planthopper Nljhe mRNA expression levels both before and after mating. Furthermore, Nljhe mRNA expression levels after mating were higher than before mating at 1,3 and 5d, indicating that mating induced Nljhe mRNA expression levels of female adults.2. Effects of sublethal doses of indoxacarb on juvenile hormone and Csjhe mRNA expression level of Chilo suppressalis (Walker) (Lepidoptera:Crambidae) nymphThe partial cDNA Sequence of juvenile hormone esterase from Chilo suppressalis were identified by reverse transcription-polymerase chain reaction (RT-PCR), a 1292bp region, which shares 78%,74% and 71% overall identity with Bombyx mori (Lepidoptera:BombMsidae), Mythimna separata (Lepidoptera: Noctuidae)and Choristoneura fumiferanai Lepidoptera.:Tortricidae)JHE homologues, respectively.Juvenile hormone Ⅲ titer in 4th instar larvae of Chilo suppressalis was significantly reduced with increasing concentration of indoxacarb, which was decreased by 37.7%,32.0%,22.3% 和 11.0% respectively, after the 3rd nymph were exposure to 0.8、0.4、0.2、0.1 g/L indoxacarb for three days compared with the untreated insects, suggesting the insecticide inhibited the synthesis of juvenile hormone. There was no significant difference in the average concentration of juvenile hormone Ⅲ in 5th instar larvae after treatment, but in addition to 0.8 g/L treatment, the JH Ⅲ average content was less than that in the 4th larvae, indicating that JH III content in penultima instar began began to decline.Compared to the control insects, the expression levels of Csjhe mRNA in 4th larve were significantly increased with increasing concentration of indoxacarb, except for 0.1 g/L indoxacarb treament. Csjhe mRNA average relative expression levels were 1.38,1.92 and 5.25 times the control levels in 4th instar larvae. With 0.1,0.2 g/L indoxacarb treament, Csjhe mRNA expression levels were 1.46,1.87 times the control in 5th instar larvae, which decreased in other concentrations treatment.3. Comparative analysis of effects of sublethal doses of indoxacarb on juvenile hormone and JHE gene mRNA expression level of Nilaparvata lugens Stal (Hemiptera:Delphacidae) adult females and Chilo suppressalis (Walker)(Lepidoptera:Crambidae) nymphThe changes of juvenile hormone Ⅲ and JHE gene mRNA expression level of Nilaparvata lugens Stal adult females before and after mating was identical with which in 4th instar larvae of Chilo suppressalis after indoxacarb exposure. The result suggested that indoxacarb inhibited the synthesis of juvenile hormone and induced the expression of JHE gene mRNA. The comparative studies showed that indoxacarb regulated reproduction in brown planthopper and stem borer by inhibiting JH synthesis Through comparative study, further revealed the regulation mechanism of indoxacarb inhibiting reproduction, and showed that indoxacarb was suitable for control pests of rice.