Ionotropic receptor 8a is involved in the attraction of Helicoverpa armigera to acetic acid.

Ionotropic receptors (IRs) were first found in Drosophila melanogaster, and derive from ionotropic glutamate receptors (iGluRs), which are implicated in detecting acids, ammonia, amine, temperature and humidity. Although IRs are involved in sensing acid odors in a few insects, such as D. melanogaster, Aedes aegypti, and Manduca sexta, the function of IRs in Helicoverpa armigera is still unknown. IR8a was confirmed to be a co-receptor associated with acid detection. From the results of phylogenetic analysis, HarmIR8a displayed high similarity compared to homologs in D. melanogaster, M. sexta, and A. aegypti, suggesting that HarmIR8a might have a consistent function as a co-receptor for acid detection. In this study, clustered regularly interspaced palindromic repeats (CRISPR) / CRISPR-associated protein 9 (Cas9)-mediated genome editing was implemented to knockout HarmIR8a for in vivo functional analysis. Electrophysiological and behavioral assays were performed to compare the differences between HarmIR8a knockout mutants and wild type individuals. From electroantennogram (EAG) analysis, we found that wild type H. armigera adults could detect short-chain carboxylic acids. In addition, wind tunnel experiments showed that 1% acetic acid attracted wild type H. armigera adults. However, acid sensing and attraction were reduced or abolished in the HarmIR8a knockout mutants. Our data suggest that HarmIR8a is important for H. armigera to detect short-chain carboxylic acids and mediate attraction behavior to acetic acid.

[Analysis of microsatellite loci from Bactrocera dorsalis based on transcriptome dataset].

The transcriptome database of the oriental fruit fly, Bactrocera dorsalis (Hendel), was used to identify the functional gene-microsatellite (EST-SSR) markers and to analyze the SSR loci information. In total, 1890 EST-SSR loci were identified, of which, 1296 SSR sequences could be used for primer design. The average distribution frequency of the transcriptomic SSRs was 1/10. 21 kb. However, these distribution frequencies varied considerably among different types of repeat SSRs. The tri-nucleotide repeat SSRs were found to have the highest frequency among the different types of repeat SSRs in the EST-SSR of B. dorsalis. Combining with other literatures, we inferred that the tri-nucleotide repeat SSRs were the most abundant EST-SSR in all of insects. In this study, 42 pairs of EST-SSR primers were designed and 18 pairs produced amplification bands of expected sizes. According to the results of other related literatures, the practices and challenges of strategy for SSR isolation from insect transcriptome databases were discussed, and the problems which should be considered in the screening of insect transcriptomic EST-SSR were put forward.