| The brown planthopper (BPH), Nilaparvata lugens (Stal)(Hemiptera: Delphacidae) is a serious pest of rice fields in Asia. In China they are mainly distributed over the Yangtze River, and have brought great economic losses to our rice production. BPH is a monophagous pest, only feeding and reproduction on the rice and wild rice. This pest has wing polymorphism, the long wing morph can fly for a long distance, and the short wing morph is not flight-capable but of a surprisingly high fecundity. A variety of factors affected wing type differentiation of BPH but the mechanism is not clear. Hormonal regulation mechanism has been widely recognized:various factors may effect the wing differentiation though the change of juvenile hormone titer.Currently for the control of brown planthopper, people mainly focused on the use of pymetrozine, imidacloprid and other pesticides. BPH has developed a high-level resistance to imidacloprid, and there are many shortcomings caused by the use of chemical pesticides. Therefore, it is urgent to develop cost-effective and environmental friendly methods for the control of BPH. Juvenile hormone epoxide hydrolase (JHEH) is a critical enzyme for degrading juvenile hormone, but the synthesis of this enzyme gene has not been research in BPH. In this paper the gene of juvenile hormone epoxide hydrolase (jheh) was cloned, the complete gene sequence was obtained. Difference of the gene expression in different periods of brachypterous and macropterous BPH strains was analysis, and the function of this gene in BPH was studied using RNAi method, which revealing the importance of jheh gene on the wing type differentiation.1. Cloning and sequence analysis of jhehThe jheh cDNA is2015bp long and contains a unique open reading frame (ORF) spanning nucleotides of1365bp. The polypeptide deduced from the ORF comprises454amino acides, containing a conserved domain of epoxide hydrolase, and also having a JHEH catalytic amino acid triplet of Asp, Glu and His, and the amino acid Tyr for consisting a negative oxygen ion hole, with the structure of being comprised of histidine (H), glycine (G), tryptophan (W) and proline (P).2. The express of the BPH jheh gene in long and short-winged strains in the different periods The study showed jheh were both expressed in the two strains. However, in the age of third instar and fouth instar, jheh expression of the long-winged BPH was significantly higher than that of the short-winged BPH.3. The expression of jheh in BPH after jheh RNAiIn this study, dsJHEH was designed according the sequence of jheh, and then was directly injected into the hemocoel of long-winged BPH. DsGFP was used for the control treatment. Results showed no significant difference of the survival rate of BPH was found between the two treatments. qPCR was used for detecting the gene expression in BPH after RNAi. It was founded that, the expression of jheh gene decreased as time passed after RNAi. One day after RNAi, the expression level dropped to40%of the control, and to8.01%six days after RNAi.4. Expression of juvenile hormone esterase gene (jhe) after jheh RNAiAfter jheh RNAi, the expression level of the gene jhe increased significantly. One day after RNAi, the expression level of jhe was2.5times of the control group, and2.91times three days after RNAi, while the expression level was basically same with the control group six days after RNAi.5. The proportional change of BPH wing type after jheh RNAiAfter jheh RNAi, the proportion of brachypterous individuals increased in long-winged BPH strains. The proportion of macropterous individuals declined to46.6%. No significant change was found for the control treatment. |
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