Interaction Between Endoparasitoid Microplitis Mediator (Hymenoptera: Braconidae) And Nucleopolyhedrovirus In Larvae Of Helicoverpa Armigera (Lepidoptera: Noctuidae)

Helicoverpa armigera could cause economic loss by feeding on cotton and tomato all over the world. H. armigera could be parasitized by Microplitis mediator and nuclear polyhedrosis virus separately. However, no research had indicated the interaction between the two parasites when they occupied the same host simultaneously. Here we reported the interaction between HearNPV and M.mediator and sequenced the transcriptome of H. armigera parasitized by M. mediator. We also researched the gene function of lectin 3 by RNAi technology. Referable value could be provided by our results for using biological control strategy reasonably and decreasing damages when using the two nature enemies of cotton bollworm concurrently. New viewpoint and theoretical basis of interaction between parasites and host were obtained from our research.The main results were shown below:1 Resistance of H. armigera to virus infection was strengthed after the parasitization by M.mediator, however, death of host due to virus infection was appeared in lower instars. The survival of parasitoid wasp declined and the development of M. mediator prolonged because of virus infection.Antagonistic effect was shown between the two parasites when the infection interval between parasitism and virus inoculation was long enough.2 Transcriptome of H. armigera parasitized by M. mediator was sequenced. Total 54,881,412 clean reads and 8.23 G raw data were obtained on the parasitized cotton bollworm larvar. 47,666,820 clean reads and 7.15 G raw data was get in the non-parasitizied host. 37,051 transcripts were annotated successfully in protein database. A total of 1,743 differentials gene were filtrated by differential genes expression analysis,1,366 genes were up-regulated and 377 genes down.3 Expression of key genes DOR STAT REL from immune pathway were up-regulated in parasitized larvar. Expression of melanization genes PPO and SERI were up-regulated whereas the expression of PPASE down-regulated. Expression of antimicrobial peptide GLV and CEC were affected by M.mediator parasitism. Expression of non-parasitized cotton worm GLV and CEC was up-regulated significantly after injection with E. coli or Metarhizium. Expression of GLV and CEC in parasitized cotton bollworm declined after injection with Metarhizium.4 Bioinformatics analysis and amino acid Multiple Alignment of LEC3 showed upper consistency with other insects. The interface of dsRNA showed that melanization genes such as TyrDO and pheo were up-regulated, IMD pathway gene DOR were also up-regulated. The enzyme of reducted glutathione were down regulated significantly. The expression of virus genes delayed after injection of LEC3 dsRNA, the morality of H. armigera caused by HearNPV declined too. The results indicate that the parasitism could weaken the virulence of NPV by inhibiting the expression of LEC3.