Behavioral and molecular response of the insect parasitic nematode Steinernema carpocapsae to plant volatiles.

Entomopathogenic nematodes (EPNs) use the chemical cues emitted by insects and insect-damaged plants to locate their hosts. Steinernema carpocapsae, a species of EPN, is an established biocontrol agent used against insect pests. Despite its promising potential, the molecular mechanisms underlying its ability to detect plant volatiles remain poorly understood. In this study, we investigated the response of S. carpocapsae infective juveniles (IJs) to 8 different plant volatiles. Among these, carvone was found to be the most attractive volatile compound. To understand the molecular basis of the response of IJs to carvone, we used RNA-Seq technology to identify gene expression changes in response to carvone treatment. Transcriptome analysis revealed 721 differentially expressed genes (DEGs) between carvone-treated and control groups, with 403 genes being significantly upregulated and 318 genes downregulated. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that the responsive DEGs to carvone attraction were mainly involved in locomotion, localization, behavior, response to stimulus, and olfactory transduction. We also identified four upregulated genes of chemoreceptor and response to stimulus that were involved in the response of IJs to carvone attraction. Our results provide insights into the potential transcriptional mechanisms underlying the response of S. carpocapsae to carvone, which can be utilized to develop environmentally friendly strategies for attracting EPNs.

The first two complete mitochondrial genomes for the genus Anagyrus (Hymenoptera, Encyrtidae) and their phylogenetic implications.

Anagyrus, a genus of Encyrtidae (Hymenoptera, Chalcidoidea), represents a successful group of parasitoid insects that attack various mealybug pests of agricultural and forestry plants. Until now, only 20 complete mitochondrial genomes have been sequenced, including those in this study. To enrich the diversity of mitochondrial genomes in Encyrtidae and to gain insights into their phylogenetic relationships, the mitochondrial genomes of two species of Anagyrus were sequenced, and the mitochondrial genomes of these species were compared and analyzed. Encyrtid mitochondrial genomes exhibit similarities in nucleotide composition, gene organization, and control region patterns. Comparative analysis of protein-coding genes revealed varying molecular evolutionary rates among different genes, with six genes (ATP8, ND2, ND4L, ND6, ND4 and ND5) showing higher rates than others. A phylogenetic analysis based on mitochondrial genome sequences supports the monophyly of Encyrtidae; however, the two subfamilies, Encyrtinae and Tetracneminae, are non-monophyletic. This study provides valuable insights into the phylogenetic relationships within the Encyrtidae and underscores the utility of mitochondrial genomes in the systematics of this family.

The complete mitochondrial genome of Exoristobia philippinensis (Hymenoptera: Chalcidoidea: Encyrtidae) and phylogenetic analysis.

Exoristobia philippinensis (Hymenoptera: Encyrtidae) is a worldwide parasitic wasp. This work presents the mitochondrial genome (mitogenome) of E. philippinensis for the first time. The complete mitochondrial genome of E. philippinensis was sequenced and annotated, which was 15,751 bp in length, and encoded 13 protein-coding genes (PCGs), 22 transfer RNA genes (tRNAs), and two ribosomal RNA genes (rRNAs). All 13 PCGs were initiated by the ATN (ATG, ATT, and ATA) codon, terminated with the stop codon TAA except for ND1 which ends with TAG. Phylogenetic analysis showed that E. philippinensis has a sister relationship with the genus Lamennaisia.

Impact of mitotype diversity on metabarcoding biodiversity estimations in Insecta and Arachnida using different sample preparation strategies.

DNA barcoding and metabarcoding have been increasingly used in species delimitation and species diversity assessment, respectively, and the molecular markers used in animals are mainly derived from mitochondrial DNA. It is well known that the phenomenon of multiple mitochondrial haplotypes within the same specimen (hereafter referred to as "mitotype diversity") may have a negative impact on the proper assessment of biodiversity by metabarcoding. However, few studies have focused on the incidence of this phenomenon and its effects on metabarcoding results using different sample preparation strategies, such as mock community construction using pooled high-throughput sequencing (HTS) data, DNA-pooling and Tissue-pooling. In this study, we investigated mitotype diversity and its influence on metabarcoding based on 398 specimens from 66 species of Insecta and 82 specimens from 16 species of Arachnida by HTS of the mitochondrial cox1 gene fragment. The results revealed that mitotype diversity was common in the studied taxa and significantly increased the number of operational taxonomic units (OTUs) using the three sample preparation strategies. The results also showed that the bioinformatics pipeline based on authentic amplicon sequence variants was more reliable than the pipeline based on OTUs. Regarding the sample preparation strategies of DNA-pooling and Tissue-pooling commonly used in metabarcoding, our results revealed that their results of metabarcoding were quite similar, and the Tissue-pooling strategy was therefore preferred because of its simplicity. Our study calls for additional attention to the interference of mitotype diversity on the results of DNA metabarcoding in biodiversity assessment.

Description of three new species and new distributional data for four species of Anagyrus (Hymenoptera: Encyrtidae) from China.

Anagyrus brevifuniculus Zu & Li, sp. nov., A. maculistigmus Zu & Li, sp. nov. and A. pseudobicolor Zu & Li, sp. nov. are described; A. tricolor (Girault) is newly recorded from the Palaearctic region and A. matritensis (Mercet) from China. New distributional data for A. fusciventris (Girault) and A. jenniferae Noyes & Hayat are also provided.