Plants employ an intricate and dynamic defense system that includes physiological, biochemical, and molecular mechanisms to counteract the effects of herbivorous attacks. In addition to their tolerance to phytotoxins, beet armyworm has quickly developed resistance to deltamethrin; a widely used pyrethroid insecticide in cotton fields. The lethal concentration (LC₅₀) required to kill 50% of the population of deltamethrin to gossypol-fed Spodoptera exigua larvae was 2.34-fold higher than the control group, suggesting a reduced sensitivity as a consequence of the gossypol diet. Piperonyl butoxide (PBO) treatment was found to synergize with deltamethrin in gossypol-fed S. exigua larvae. To counteract these defensive plant secondary metabolites, beet armyworm elevates their production of detoxification enzymes, including cytochrome P450 monooxygenases (P450s). Gossypol-fed beet armyworm larvae showed higher 7-ethoxycoumarin-O-deethylase (ECOD) activities and exhibited enhanced tolerance to deltamethrin after 48 and 72 h when compared to the control. Moreover, gossypol pretreated S. exigua larvae showed faster weight gain than the control group after transferring to a deltamethrin-supplemented diet. Meanwhile, gossypol-induced P450s exhibited high divergence in the expression level of two P450 genes: CYP6AB14 and CYP9A98 in the midgut and fat bodies contributed to beet armyworm tolerance to deltamethrin. Knocking down of CYP6AB14 and CYP9A98, via double-stranded RNAs (dsRNA) in a controlled diet, rendered the larvae more sensitive to the insecticide. These data demonstrate that generalist insects can exploit secondary metabolites from host plants to enhance their defense systems against other toxic chemicals. Impairing this defense pathway by RNA interference (RNAi) holds a potential to eliminate the pest’s tolerance to insecticides and, therefore, reduce the required dosages of agrochemicals in pest control.

RNA secondary structure elements in the mRNA 3ʹ-untranslated regions (3ʹUTR) play important roles in post-transcriptional regulation. RNA structure elements in the viral RNA provide valuable model for studying diverse regulation mechanisms. Herpesvirus genomes are double-stranded DNA with GC-rich sequences, which can be transcribed into abundant GC-rich RNAs. It is valuable to explore the structures and function of those GC-rich RNAs. We identified a G₂-quadruplex-forming sequence named PQS18-1 in the 3ʹUTR of the unique immediate early gene of Pseudorabies virus (PRV), an important member of alphaherpesvirus subfamily. The RNA PQS18-1 was folded into parallel G-quadruplex structure, enhancing gene expression. Both non-G-quadruplex mutant and G₃-quadruplex mutant in the 3ʹUTR showed lower gene expression level than the wildtype G₂-quadruplex. A chemical compound destroyed PQS18-1 G₂-quadruplex and suppressed gene expression, accordingly reducing PRV replication by one titre in the PK15 cells at 24 hours post infection. Our findings indicated that the RNA G₂-quadruplex in 3ʹUTR was essential for high expression of IE180 gene, and it could be a specific post-transcription regulation element in response to small molecules or other macromolecules. This study discovers a novel RNA G₂-quadruplex in the 3ʹUTR of an immediate early gene of alphaherpesvirus, and provides a new nucleic acid target for anti-virus drug design.

Graphene oxide (GO), as a promising synergistic agent of pesticides against pests, exhibits broad application prospects in the agricultural field. However, the synergistic mode of GO on acaricides remains unclear. Herein, an acaricide delivery nanosystem using GO nanosheets as nanocarriers, for the first time, was constructed and characterized to deliver four global top-selling acaricides (avermectin, bifenazate, etoxazole and spirodiclofen) to control Tetranychus cinnabarinus (a crop-threatening spider mite pest). The results showed that GO adsorbed on and impaired the cuticle of mites by binding to a cuticle protein (CPR) and inhibiting the expression of the CPR gene, thereby increasing the cuticle permeability of mites, which significantly enhanced the efficiency of acaricides. Additionally, silencing the CPR gene by RNAi resulted in dehydration, disturbed the construction of the cuticle layer, and increased the cuticle permeability and sensitivity of mites to GO–acaricides, which was consistent with the synergistic phenotype of GO on acaricides, demonstrating that the molecular mechanism of synergistic effects of GO on acaricides against T. cinnabarinus was mediated by the low-expressed CPR gene. The use of GO–acaricides in agriculture will reduce the application of chemical acaricides and their adverse impacts on public health and the environment.

The beet armyworm, Spodoptera exigua (Hubner), is one of the major crop pests and is a target for current pest control approaches using insecticides. In this study three cuticular protein genes CPG316, CPG860 and CPG4855 have been cloned from 0 h pupal integument of S. exigua through race PCR Strategy. The deduced amino acid sequences were found to contain the RR-2 consensus region of other insect cuticular proteins and construct phylogenetic trees for each protein. Using quantitative RT-PCR, the developmental expression of the three genes through several larval and the early pupal stages was studied. All three genes contribute to the endocuticle although CPG316 may have a different role from the other two genes. All three newly isolated genes were analyzed and their functions were determined by using direct injection of the dsRNA into early 5^th instar larvae. All genes are expressed in the larvae and early pupae but in different patterns. Furthermore, phenotypic results show that these genes have differing effects on the development of cuticle, its flexibility and a big role in metamorphosis in both larval and pupal stages.