Behavioral Responses Of Chrysopa Pallens (Rambur)to Ragweed Volatiles And Analysis Of Orco Gene Function

Chrysopa pallens(Rambur)is an excellent natural enemy resource,which has a significant effect of controlling the number of various insect populations in nature.In the ragweed-occurring area,it was found that the smell of ragweed can repel swarms of C.pallens,which played a protective role in the accumulation of Ophraella communa-the natural enemy of ragweed.In this study,in order to ascertain the behavioral regulation of ragweed volatiles on C.pallens,the odorant compounds that had a tendency to act on adults of C.pallens were screened out by EAG responses and behavioral tests of ragweed volatiles.Based on the C.pallens transcriptome,37 ORs were identified,and their expression patterns in different tissues of C.pallens adults were detected.The gene structure of C.pallens Orco was analyzed and its function was verified.The main findings are as follows:1.Physiological studies performed on C.pallens female and male adults using EAG responses and Y-tube tests were measured.The results showed that all the nine odor compounds in the volatile of ragweed could induce EAG response of female and male adults.Among which,the EAG response value to alpha-pinene,nonanal,camphor and limonene was higher.However,there was no significant difference in the EAG responses between the female and male adults.The Y-tube test results displayed that C.pallens showed a significant trend towards alpha-pinene and limonene,and a significant avoidance against nonanal and camphor.2.Based on the RNA-seq datas of the antennae,37 ORs genes were identified by bioinformatics analysis,and the qRT-PCR experiment was used to study the ORs expression in C.pallens female,male antennae,head,chest,abdomen,foot and wing.The results showed that 28 ORs were highly or specially expressed in the female and male antennae,which may be considered to have an important role in the olfactory recognition process.3.The total length of the C.pallens Orco identified by RNA-seq was 1467 bp,encoding a total of 488 amino acids.The biological analysis of C.pallens Orco showed that it had 7 transmembrane structures,the molecular weight of the coding protein was 55.53 kda,and the isoelectric point PI was 7.93 with 64 phosphorylation sites.The tertiary structure of the protein is mainly composed of a helix and random coil winding and folding.The development tree of Orco showed that the C.pallens Orco were closely related to other Coleoptera species.The results of Orco expression analysis showed that the Orco was highly expressed in the antennae and little in the wings of female and male adults.The Orco was silenced by RNAi technology,and the qRT-PCR analysis showed that the expression decreased significantly 24 hours after ds RNA injection.The results of EAG analysis showed that silencing of Orco would reduce the potential change of nonanal.Therefore,it can be speculated that the Orco plays an important role in the regulation of the behavior of C.pallens.