Genomic analysis of two Chinese isolates of hyphantria cunea nucleopolyhedrovirus reveals a novel species of alphabaculovirus that infects hyphantria cunea drury (lepidoptera: arctiidae).

BACKGROUND: Baculoviruses act as effective biological control agents against the invasive pest Hyphantria cunea Drury. In this study, two Chinese Hyphantria cunea nucleopolyhedrovirus (HycuNPV) isolates, HycuNPV-BJ and HycuNPV-HB, were deep sequenced and compared with the Japanese isolate, HycuNPV-N9, to determine whole-genome level diversity and evolutionary history. RESULTS: The divergence of the phylogenetic tree and the K2P distances based on 38 core-gene concatenated alignment revealed that two Chinese HycuNPV isolates were a novel species of Alphabaculovirus that infected Hyphantria cunea in China. The gene contents indicated significant differences in the HycuNPV genomes between the Chinese and Japanese isolates. The differences included gene deletions, acquisitions and structural transversions, but the main difference was the high number of single nucleotide polymorphisms (SNPs). In total, 10,393 SNPs, corresponding to approximately 8% of the entire HycuNPV-N9 genome sequence, were detected in the aligned reads. By analyzing non-synonymous variants, we found that hotspot mutation-containing genes had mainly unknown functions and most were early expressing genes. We found that the hycu78 gene which had early and late promoter was under positive selection. Biological activity assays revealed that the infectivity of HycuNPV-HB was greater than that of HycuNPV-BJ, and the killing speed of HycuNPV-HB was faster than that of HycuNPV-BJ. A comparison of molecular genetic characteristics indicated that the virulence differences between the two isolates were affected by SNP and structural variants, especially the homologous repeat regions. CONCLUSIONS: The genomes of the two Chinese HycuNPV isolates were characterized, they belonged to a novel species of Alphabaculovirus that infected Hyphantria cunea in China. We inferred that the loss or gain of genetic material in the HycuNPV-HB and HycuNPV-BJ genomes resulted in new important adaptive capabilities to the H. cunea host. These results extend the current understanding of the genetic diversity of HycuNPV and will be useful for improving the applicability of this virus as a biological control agent.

Analysis of antennal transcriptome and odorant binding protein expression profiles of the recently identified parasitoid wasp, Sclerodermus sp.

We constructed an antennal transcriptome of the parasitoid wasp, Sclerodermus sp. (Hymenoptera: Bethylidae). Our analysis of the transcriptome yielded 51,830,552 clean reads. A total of 46,269 unigenes were assembled, among which 29,582 unigenes exhibited significant similarity (E-values≤10(-5)) to sequences in the NCBI nonredundant protein database. Gene ontology (GO) and cluster of orthologous groups (COG) analyses were used for the functional classification of these unigenes. We identified ten odorant binding proteins (OBPs), ten chemosensory proteins (CSPs), eight olfactory receptors (ORs), three ionotropic receptors (IRs), six gustatory receptors (GRs), and two sensory neuron membrane proteins (SNMPs). The expression profiles of the ten OBPs were determined based on a qPCR analysis of RNA extracted from the antennae, legs, and abdomens of wingless and winged female adults and whole larvae and pupae. The highest levels of OBP5, OBP6, OBP7, and OBP9 expression were observed in the antennae of adult females. The highest levels of OBP1, OBP2, and OBP4 expression were observed in the abdomen of winged females. The highest levels of OBP3 and OBP10 expression were observed in larvae and pupae, respectively, whereas OBP8 was expressed at high levels in both larvae and pupae. Our findings establish a foundation for future studies of the molecular mechanisms of chemosensory perception in Sclerodermus sp.

Analysis of chemosensory gene families in the beetle Monochamus alternatus and its parasitoid Dastarcus helophoroides.

We assembled antennal transcriptomes of pest Monochamus alternatus and its parasitoid Dastarcus helophoroides to identify the members of the major chemosensory multi-gene families. Gene ontology (GO) annotation indicated that the relative abundance of transcripts associated with specific GO terms was highly similar in the two species. In chemosensory gene families, we identified 52 transcripts encoding putative odorant-binding proteins (OBPs), 19 chemosensory proteins (CSPs), 10 olfactory receptors (ORs), 8 ionotropic receptors (IRs), 2 gustatory receptors (GRs), and 5 sensory neuron membrane proteins (SNMPs) in these two transcriptomes. Predicted protein sequences were compared with Dendroctonus ponderosae, Tribolium castaneum and Drosophila melanogaster. The results of phylogenetic trees showed that some clusters included only OBPs or CSPs from D. helophoroides, some clusters included only OBPs or CSPs from M. alternatus, while some clusters included OBPs or CSPs from both M. alternatus and D. helophoroides. The identification of the chemosensory genes and the phylogenetic relationship of these genes between two species might provide new ideas for controlling M. alternatus and improving current strategies for biological control.