Characterization of the Adult Head Transcriptome and Identification of Migration and Olfaction Genes in the Oriental Armyworm Mythimna separate

Transcriptomic analysis of Mythimna separata ovaries and identification of genes involved in reproduction

The migratory insect Mythimna separata is a major pest of grain crops in Asia. Unfortunately, the molecular mechanisms that control and regulate reproduction in this species remain unclear. In this study, transcriptome sequencing was utilized to identify genes associated with ovary development and oogenesis. Clean sequences totaling 117.71 Gb were assembled into 178,534 unigenes with a mean length of 647.37 bp and N50 length of 837 bp. Transcriptome analysis showed that 7921 unigenes were significantly expressed in ovaries with 4403 and 3518 unigenes up- and down-regulated, respectively. Enrichment analysis with the Kyoto Encyclopedia of Genes and Genomes database suggested that 729 differentially expressed genes were significantly enriched in the top 20 pathways (q-values <0.05). Twenty genes were associated with ovary development and oogenesis and included lipases, Nanos, small heat shock proteins (sHsps) and histones; these were further verified by qRT-PCR and may play essential roles in M. separata reproduction. Collectively, our findings reveal underlying mechanisms of M.separata reproduction and may lead to RNAi-based management strategies targeting reproductive physiology.

Identification of Odorant-Binding and Chemosensory Protein Genes in Mythimna separata Adult Brains Using Transcriptome Analyses

Large numbers of chemosensory genes have been identified in the peripheral sensory organs of the pest Mythimna separata (Walker) to increase our understanding of chemoreception-related molecular mechanisms and to identify molecular targets for pest control. Chemosensory-related genes are expressed in various tissues, including non-sensory organs, and they play diverse roles. To better understand the functions of chemosensory-related genes in non-sensory organs, transcriptomic analyses of M. separata brains were performed. In total, 29 odorant-binding proteins (OBPs) and 16 chemosensory proteins (CSPs) putative genes were identified in the transcriptomic data set. The further examination of sex- and tissue-specific expression using RT-PCR suggested that eight OBPs (OBP5, -7, -11, -13, -16, -18, -21, and -24) and eight CSPs (CSP2–4, -8, CSP10–12, and -15) genes were expressed in the brain. Furthermore, bands representing most OBPs and CSPs could be detected in antennae, except for a few that underwent sex-biased expression in abdomens, legs, or wings. An RT-qPCR analysis of the expression profiles of six OBPs (OBP3–5, -9, -10, and -16) and two CSPs (CSP3 and CSP4) in different tissues and sexes indicated that OBP16 was highly expressed in male brain, and CSP3 and CSP4 were female-biased and highly expressed in brain. The expression levels of OBP5 and OBP10 in brain were not significantly different between the sexes. The findings expand our current understanding of the expression patterns of OBPs and CSPs in M. separata sensory and non-sensory tissues. These results provide valuable reference data for exploring novel functions of OBPs and CSPs in M. separata and may help in developing effective biological control strategies for managing this pest by exploring novel molecular targets.

Olfactory coding of intra- and interspecific pheromonal messages by the male Mythimna separata in North China

Moths often use multi-component pheromones with fixed ratios to keep intraspecific communication and interspecific isolation. Unusually, the Oriental armyworm Mythimna separata in North China use only Z11-16:Ald as the essential component of its sex pheromone to find mates. To understand how this species keeps behavioral isolation from other species sharing Z11-16:Ald as a major pheromone component, we study the olfactory coding of intra- and interspecific pheromonal messages in the males of M. separata. Firstly, we functionally characterized the long trichoid sensilla in male antennae by single sensillum recording. Two types of sensilla were classified: the A type sensilla responded to Z11-16:Ald and Z9-14:Ald, and the B type sensilla mainly to Z9-14:Ald, and also to Z11-16:Ac, Z11-16:OH, and Z9-16:Ald. Next, we examined the glomerulus responses in the antennal lobes to these compounds by using in vivo optical imaging. The results showed that among the three subunits of the macroglomerular complex (MGC), Z11-16:Ald activated the cumulus, Z9-14:Ald activated the dorso-anterior and the cumulus, Z11-16:OH and Z11-16:Ac activated the dorso-anterior and dorso-posterior, respectively. However, Z9-16:Ald activated an ordinary glomerulus. Thirdly, we tested the behavioral responses of the males to these compounds in the wind tunnel. Addition of Z9-14:Ald at the ratio of 1:10 greatly reduced the attractiveness of Z11-16:Ald, addition of Z9-16:Ald or Z11-16:OH at the ratio of 1:1 also had behavioral antagonistic effects, while addition of Z11-16:Ac had no effect on the attractiveness of Z11-16:Ald. Finally, we used antennal transcriptome data and the Xenopus expression system to identify the receptor of Z9-14:Ald in M. separata. The Xenopus oocytes co-expressing MsepOR2 and MsepORco showed a strong response to Z9-14:Ald. Two-color fluorescence in situ hybridization validated that the cells expressing MsepOR2 and MsepOR3, tuned to Z9-14:Ald and Z11-16:Ald respectively, were localized in the different sensilla of male antennae. Comparing the sex pheromone communication channel of the related species, our results suggest that the conserved olfactory pathways for behavioral antagonists play a crucial role in behavioral isolation of noctuid species.

The de novo transcriptome of workers head of the higher group termite Globitermes sulphureus Haviland (Blattodea: Termitidae)

The subterranean termite Globitermus sulphureus is an important Southeast Asian pest with limited genomic resources that causes damages to agriculture crops and building structures. Therefore, the main goal of this study was to survey the G. sulphureus transcriptome composition. Here, we performed de novo transcriptome for G. sulphureus workers’ heads using Illumina HiSeq paired-end sequencing technology. A total of 88, 639, 408 clean reads were collected and assembled into 243, 057 transcripts and 193, 344 putative genes. The transcripts were annotated with the Trinotate pipeline. In total, 27, 061 transcripts were successfully annotated using BLASTX against the SwissProt database and 17, 816 genes were assigned to 47, 598 GO terms. We classified 14, 223 transcripts into COG classification, resulting in 25 groups of functional annotations. Next, a total of 12, 194 genes were matched in the KEGG pathway and 392 metabolic pathways were predicted based on the annotation. Moreover, we detected two endogenous cellulases in the sequences. The RT-qPCR analysis showed that there were significant differences in the expression levels of two genes β-glucosidase and endo-β-1,4-glucanase between worker and soldier heads of G. sulphureus. This is the first study to characterize the complete head transcriptome of a higher termite G. sulphureus using a high-throughput sequencing. Our study may provide an overview and comprehensive molecular resource for comparative studies of the transcriptomics and genomics of termites.

Design, synthesis, insecticidal activity and 3D-QSR study for novel trifluoromethyl pyridine derivatives containing an 1,3,4-oxadiazole moiety

A series of trifluoromethyl pyridine derivatives containing 1,3,4-oxadiazole moiety was designed, synthesized and bio-assayed for their insecticidal activity. The result of bio-assays indicated the synthesized compounds exhibited good insecticidal activity against Mythimna separata and Plutella xylostella, most of the title compounds show 100% insecticidal activity at 500 mg L⁻¹ and >80% activity at 250 mg L⁻¹ against the two pests. Compounds E18 and E27 showed LC₅₀ values of 38.5 and 30.8 mg L⁻¹ against Mythimna separata, respectively, which were close to that of avermectin (29.6 mg L⁻¹); compounds E5, E6, E9, E10, E15, E25, E26, and E27 showed 100% activity at 250 mg L⁻¹, which were better than chlorpyrifos (87%). CoMFA and CoMSIA models with good predictability were proposed, which revealed the electron-withdrawing groups with an appropriate bulk at 2- and 4-positions of benzene ring could enhance insecticidal activity.

Novel trifluoromethyl pyridine derivatives bearing 1,3,4-oxadiazole whereas synthesized, their which showed good insecticidal activity; a 3D-QSAR model with good predictability was is proposed.