Transcriptomic analysis of pre-diapause larvae of Chilo suppressalis (Walker) (Lepidoptera: Pyralidae) in natural populations

De novo transcriptome assembly and differential gene expression analysis in different developmental stages of Agriotes sputator (click beetle)

Wireworms, the larva of click beetle (Agriotes species), are one of the most destructive pests of horticultural crops in North America, responsible for considerable economic losses in Canada. Agriotes sputator (A. sputator) species is a predominant wireworm pest attacking potato fields in Eastern Canada. However, no information about its genome-wide gene expression profile, specifically for the genes involved with development is available to date. Therefore, we generated the transcriptome profile of A. sputator during five developmental stages, including the three larval stages and adult male and female click beetle. Out of 714.7 million raw reads, de novo assembly generated 564,561 transcripts. The data were subjected to differential expression analysis using DESeq2, gene ontology, annotation, and pathway analyses. A total of 34,709 differentially expressed genes (DEGs) were significant (log2 fold change > 2, padj < 0.05) across the developmental stages. Functional analysis of DEGs identified development signaling, metabolism, transport, cellular mechanisms, and drug metabolism (cytochrome p450) pathways. This study provides comprehensive sequence resources and potential gene differences at different developmental stages of A. sputator. These findings will represent a major step towards developing sustainable methods to control this widely distributed pest in agricultural fields.

Enhancing bioactivity of Callistemon citrinus (Curtis) essential oil through novel nanoemulsion formulation

The main focus of this study was to create a stable and efficient nanoemulsion (NE) using Callistemon citrinus essential oil (EO). Various factors affecting the NE's stability were optimized including oil %, Tween 80%, time of sonication, and its accelerated stability was examined. The research also considered the antibacterial, antifungal, and larvicidal effects of the optimized NE (B10). The optimum NE stood out for its stability, featuring a particle size of 33.15 ± 0.32 nm. Analysis via IR spectroscopy confirmed successful EO encapsulation in B10. The formulation remained stable for six months, with B10 showing significantly higher antibacterial and antifungal potency compared to the pure oil. When samples were subjected to tests against Fusarium oxysporum, B10 exhibited a MIC value of 62.5 mg/mL, whereas the pure oil showed a MIC value of 250 mg/mL. This indicates that the B10 formulation was 50 times more effective than the EO. In terms of antibacterial activity against Escherichia coli, the MIC value was 0.256 mg/mL for B10 and 4 mg/mL for the EO. Also, pure oil and B10 displayed larvicidal effects against Chilo suppressalis (Walker) larvae, with B10 eliminating 95.2% of larvae in 48 h. Overall, stable and optimum C. citrinus NE with its strong antimicrobial qualities, shows promise as an effective fungicide and insecticide.

Time-Series Transcriptomic Analysis Reveals the Molecular Profiles of Diapause Termination Induced by Long Photoperiods and High Temperature in Chilo suppressalis

Survival and adaptation to seasonal changes are challenging for insects. Many temperate insects such as the rice stem borer (Chilo suppressalis) overcome the adverse situation by entering diapause, wherein development changes dynamically occur and metabolic activity is suppressed. The photoperiod and temperature act as major environmental stimuli of diapause. However, the physiological and molecular mechanisms that interpret the ecologically relevant environmental cues in ontogenetic development during diapause termination are poorly understood. Here, we used genome-wide high-throughput RNA-sequencing to examine the patterns of gene expression during diapause termination in C. suppressalis. Major shifts in biological processes and pathways including metabolism, environmental information transmission, and endocrine signalling were observed across diapause termination based on over-representation analysis, short time-series expression miner, and gene set enrichment analysis. Many new pathways were identified in diapause termination including circadian rhythm, MAPK signalling, Wnt signalling, and Ras signalling, together with previously reported pathways including ecdysteroid, juvenile hormone, and insulin/insulin-like signalling. Our results show that convergent biological processes and molecular pathways of diapause termination were shared across different insect species and provided a comprehensive roadmap to better understand diapause termination in C. suppressalis.