Comparative study of the sublethal effects of indoxacarb on juvenile hormone titer and juvenile hormone esterase mRNA expression of Nilaparvata lugens and Chilo suppressalis in rice

Both the rice stem borer, Chilo suppressalis, and the brown planthopper, Nilaparvata lugens are important rice pests. The study is a comparative analysis on the effects of indoxacarb on the pest's juvenile hormone OH) titer and juvenile hormone esterase (JHE) mRNA expression. RT-PCR and RACE were used to amplify the full length Csjhe (JHE of C suppressalis) cDNA from C suppressalis. The full length cDNA is 1841 bp in length and contains a 1734 bp open reading encoding 577 amino acid residues. An amino acid sequence alignment shows that Csjhe shares high identity with other three other lepidopterans homologues including Manduca sexta, Bombyx moil, and Choristoneura ftniferana. JH III titer in 4th instar larvae of C. suppressalis was significantly reduced with 0.1, 0.2, 0.4 and 0.8 g/L indoxacarb, which were decreased by 11.0%, 223%, 32.0% and 37.7% respectively, the expression levels of Csjhe mRNA were 1.38, 1.92 and 5.25 times the control levels in 4th instar larvae with 0.2, 0.4 and 0.8 g/L indoxacarb. Similarly, all of the tested concentrations of indoxacarb caused a significant decrease in JH III titer of N. lugens adult females after indoxacarb treatments, Nljhe (JHE of N. lugens) mRNA average expression levels were 4.8, 5.0 and 4.4 times before mating and 6.5, 7.6 and 53 times after mating compared to the control at 1, 3 and 5 days, respectively. The comparative studies of the effects of indoxacarb on JH Ill titer and JHE mRNA further have a significance to a guided integrated pest management. (C) 2017 Korean Society of Applied Entomology, Taiwan Entomological Society and Malaysian Plant Protection Society. Published by Elsevier B.V. All rights reserved.