Chemosensory proteins (CSP) are a class of acidic soluble proteins which have various functions in chemoreception, resistance and immunity, but we still have very little knowledge on this gene family in fig wasps, a peculiar insects group (Hymenoptera, Chalcidoidea) that shelter in the fig syconia of Ficus trees. Here, we made the first comprehensive analysis of CSP gene family in the 11 fig wasps at whole-genome level. We manually annotated 104 CSP genes in the genomes of the 11 fig wasps, comprehensively analyzed them in gene characteristics, conserved cysteine patterns, motif orders, phylogeny, genome distribution, gene tandem duplication, and expansion and contraction patterns of the gene family. We also approximately predicted the gene expression by codon adaptation index analysis. Our study shows that the CSP gene family is conserved in the 11 fig wasps; the CSP gene numbers in pollinating fig wasps are less than in non-pollinating fig wasps, which may be due to their longer history of adaptation to fig syconia; the expansion of CSP gene in two non-pollinating fig wasps, Philotrypesis tridentata and Sycophaga agraensis, may be a species-specific phenomenon. These results provide us with useful information for understanding the evolution of the CSP gene family of insects in diverse living environments.

Fig wasps are a group of insects (Hymenoptera: Chalcidoidea) that live in the compact syconia of fig trees (Moraceae: Ficus). Accurate classification and phylogenetic results are very important for studies of fig wasps, but the taxonomic statuses of some fig wasps, especially the non-pollinating subfamilies are difficult to determine, such as Epichrysomallinae and Sycophaginae. To resolve the taxonomic statuses of Epichrysomallinae and Sycophaginae, we obtained transcriptomes and mitochondrial genome (mitogenome) data for four species of fig wasps. These newly added data were combined with the data of 13 wasps (data on 11 fig wasp species were from our laboratory and two wasp species were download from NCBI). Based on the transcriptome and genome data, we obtained 145 single-copy orthologous (SCO) genes in 17 wasp species, and based on mitogenome data, we obtained 13 mitochondrial protein-coding genes (PCGs) for each of the 17 wasp species. Ultimately, we used 145 SCO genes, 13 mitochondrial PCGs and combined SCO genes and mitochondrial genes data to reconstruct the phylogenies of fig wasps using both maximum likelihood (ML) and Bayesian inference (BI) analyses. Our results suggest that both Epichrysomallinae and Sycophaginae are more closely related to Agaonidae with a high statistical support.

Wolbachia are widely distributed in arthropods and nematodes, acquiring nutrients from the hosts, and inducing remarkable reproductive modulations on the hosts. To investigate the interaction of Wolbachia and insects, Wolbachia are often artificially eliminated from Wolbachia-infected hosts, which may produce negative effects of antibiotics. In the present study, based on the transcriptomic data of a fig wasp species Ceratosolen solmsi with two sibling lineages, one natively infected and the other noninfected with Wolbachia, we investigated the expression patterns of genes. The comparison results of differently expressed genes (DEGs) between Wolbachia infected and noninfected samples show that males have many more DEGs than females. The male unique upregulated genes are enriched in biological processes mainly related to biosynthesis, transport, positive regulation of I-kappaB kinase/NF-kappaB signaling, MAPK cascade, and pathogenesis; the male unique downregulated genes are enriched in biological processes mainly related to transport, oxidation–reduction, cellular responses to oxidative stress, lipid oxidation, cytoskeleton organization, actin filament-based process, and localization. In addition, for the Wolbachia’s gene expression, the number of genes up-regulated in males is higher than that in females. The results revealed divergent patterns of the host–Wolbachia interactions between males and females in the fig wasp species.