Characteristics of the Accessible Chromatin Landscape and Transcriptome under Different Temperature Stresses in <i>Bemisia tabaci</i>

Bemisia tabaci is an important invasive pest with worldwide distribution and strong temperature tolerance. Previous studies have shown that temperature tolerance varies significantly between the different invasive populations. Several key factors involved in epigenetic regulation have been identified and verified in B. tabaci; therefore, epigenetic adaptation mechanisms may also exist. This study aimed to detect changes in the chromatin accessibility landscape and genome-wide transcriptome under different temperature stresses in B. tabaci. Assay for transposase-accessible chromatin with high-throughput sequencing and RNA-seq analyses indicated that transcriptional activity of the genes strongly correlates with chromatin accessibility. Chromatin transcription-activated gene expression regulation is dominant during high-temperature stress in B. tabaci, mainly through the transcriptional repression of genes related to low-temperature stress resistance. Furthermore, B. tabaci resists low-temperature stress by regulating enzyme activities and withstands high-temperature stress by regulating metabolism and synthesis of organic substances, both achieved by altering chromatin accessibility. In summary, this study provides a theoretical basis for exploring changes in gene expression and chromatin accessibility under different temperature stresses, offering a new approach to unravelling regulatory mechanisms underlying the onset of molecular regulation in response to various temperature stress conditions

Krüppel-homologue 1 regulates the development of Tuta absoluta and its cascade regulation pattern in the juvenile hormone signalling pathway

Tomato leaf miner, Tuta absoluta (Meyrick), is one of the most destructive quarantine pests globally. It has been confirmed that Krüppel-homologue 1 (kr-h1) plays a key role in the regulation of juvenile hormone (JH). However, it is unclear how kr-h1 regulates the synthesis of JH and its cascade regulation pattern in tomato leaf miner. Here, we obtained the six JH signalling genes (kr-h1, Methoprene-tolerant, Forkhead box O, Juvenile acid methyltransferase, Juvenile hormone esterase and Fatty acid synthase 2), and applied RNA interference to explore the role of kr-h1 and the seven genes (plus Vitellogenin) regulation relationship in T. absoluta. Bioinformatics analysis revealed the structural characteristics of kr-h1 protein and JH receptor Met, which contained eight C2H2 zinc finger structures and three typical domains of the bHLH-PAS family, respectively. The expression levels of Met and Vg were upregulated after RNAi of kr-h1 gene, while the gene levels of JHAMT and FAS2 were downregulated. Furthermore, topical application of JH analogue to second instar larvae could induce the expression of kr-h1 and inhibit the expression of Met. Our study reveals the mechanism by which kr-h1 regulates JH pathway genes, which could be applied to control the growth of tomato leaf miners

Phototactic Changes in <i>Phthorimaea absoluta</i> Long-Wavelength Opsin Gene Mutants (<i>LW2^−/−</i>) and Short-Wavelength Opsin Gene Mutant (<i>BL^−/−</i>) Strains

Phthorimaea absoluta (Meyrick) is an invasive pest that has caused damage to tomatoes and other crops in China since 2017. Pest control is mainly based on chemical methods that pose significant threats to food safety and environmental and ecological security. Light-induced control, a green prevention and control technology, has gained attention recently. However, current light-trapping technology is non-specific, attracting targeted pests alongside natural enemies and non-target organisms. In this study, we characterized the phototactic behavior of tomato leaf miners for the development a specific light-trapping technology for pest control. In situ hybridization revealed opsin expression throughout the body. Furthermore, we investigated the tropism of pests (wild T. absoluta, Toxoptera graminum, and Bemisia tabaci) and natural enemies (Nesidiocoris tenuis and Trichogramma pintoi) using a wavelength-lamp tropism experiment. We found that 365 ± 5 nm light could accurately trap wild P. absoluta without trapping natural enemies and other insects. Finally, we analyzed the phototactic behavior of the mutant strains LW2(−/−) and BL(−/−). LW2 and BL mutants showed significant differences in phototactic behavior. The LW2(−/−) strain was attracted to light at 390 ± 5 nm and the BL(−/−) strain was unresponsive to any light. Our findings will help to develop specific light-trapping technology for controlling tomato leaf miners, providing a basis for understanding pest population dynamics and protecting crops against natural enemies