Juvenile hormone regulation of microRNAs is mediated by E75 in the Dengue vector mosquito Aedes aegypti

Lufenuron affects the fecundity of Panonychus citri by regulating the methyl farnesoate-ponasterone A network

In insects, the juvenile hormone (JH) and 20-hydroxyecdysone (20E) pathways jointly regulate fecundity, but only methyl farnesoate (MF) and ponasterone A exist in mites. Comparative transcriptomic analysis in Panonychus citri showed that E75B was significantly downregulated when exposed to lufenuron. Knockdown of E75B significantly affects the expression of vitellogenin (Vg), Fushi tarazu factor 1 (Ftz-f1) and juvenile hormone acid O-methyltransferase (JHAMT), reducing fecundity in mites. The knockdown of Ftz-f1 produced a more significant effect than the knockdown of E75B, indicating that the ponasterone A pathway positively regulates fecundity in P. citri. After the knockdown of JHAMT, the expression levels of both Vg and Ftz-f1 and fecundity were significantly increased, along with the inhibition of Kr-h1, suggesting that JHAMT was negatively correlated with fecundity in the regulatory network. Knockdown of Kr-h1 inhibited the expression of Vg and Ftz-f1 and fecundity, and whether the drop in fecundity is caused by Kr-h1 or Ftz-f1 is unclear. Subsequent feeding with MF induced Kr-h1 and Vg expression, whereas no significant effects were observed for JHAMT and Ftz-f1. Therefore, the MF pathway stimulates fecundity independently. RNA interference (RNAi) showed that JHAMT and Ftz-f1 inhibited each other, resulting in opposite effects of MF and ponasterone A pathways on steady-state fecundity when either factor changed. Meanwhile, JHAMT knockdown led to increased fecundity, indicating that the stimulating effect of the ponasterone A pathway was greater than the inhibiting effect of the MF pathway, and demonstrating the dominant role of the ponasterone A pathway. Therefore, the interaction between JHAMT and Ftz-f1 may be closely associated with the maintenance of MF-ponasterone A regulatory network homeostasis and is involved in the reduction of fecundity in P. citri induced by exposure to lufenuron.

Endocrine factors modulating vitellogenesis and oogenesis in insects: An update

The endocrine system plays a pivotal role in shaping the mechanisms that ensure successful reproduction. With over a million known insect species, understanding the endocrine control of reproduction has become increasingly complex. Some of the key players include the classic insect lipid hormones juvenile hormone (JH) and ecdysteroids, and neuropeptides such as insulin-like peptides (ILPs). Individual endocrine factors not only modulate their own target tissue but also play crucial roles in crosstalk among themselves, ensuring successful vitellogenesis and oogenesis. Recent advances in omics, gene silencing, and genome editing approaches have accelerated research, offering both fundamental insights and practical applications for studying in-depth endocrine signaling pathways. This review provides an updated and integrated view of endocrine factors modulating vitellogenesis and oogenesis in insect females.

Regulation of insect behavior by non-coding RNAs

The adaptation of insects to environments relies on a sophisticated set of behaviors controlled by molecular and physiological processes. Over the past several decades, accumulating studies have unveiled the roles of non-coding RNAs (ncRNAs) in regulating insect behaviors. ncRNAs assume particularly pivotal roles in the behavioral plasticity of insects by rapidly responding to environmental stimuli. ncRNAs also contribute to the maintenance of homeostasis of insects by fine-tuning the expression of target genes. However, a comprehensive review of ncRNAs' roles in regulating insect behaviors has yet to be conducted. Here, we present the recent progress in our understanding of how ncRNAs regulate various insect behaviors, including flight and movement, social behavior, reproduction, learning and memory, and feeding. We refine the intricate mechanisms by which ncRNAs modulate the function of neural, motor, reproductive, and other physiological systems, as well as gene expression in insects like fruit flies, social insects, locusts, and mosquitos. Furthermore, we discuss potential avenues for future studies in ncRNA-mediated insect behaviors.

Genome-wide analysis of Panonychus citri microRNAs with a focus on potential insecticidal activity of 4 microRNAs to eggs and nymphs

Panonychus citri McGregor (Acari: Tetranychidae), a destructive citrus pest, causes considerable annual economic losses due to its short lifespan and rapid resistance development. MicroRNA (miRNA)-induced RNA interference is a promising approach for pest control because of endogenous regulation of pest growth and development. To search for miRNAs with potential insecticidal activity in P. citri, genome-wide analysis of miRNAs at different developmental stages was conducted, resulting in the identification of 136 miRNAs, including 73 known and 63 novel miRNAs. A total of 17 isomiRNAs and 12 duplicated miRNAs were characterized. MiR-1 and miR-252-5p were identified as reference miRNAs for P. citri and Tetranychus urticae. Based on differential expression analysis, treatments with miR-let-7a and miR-315 mimics and the miR-let-7a antagomir significantly reduced the egg hatch rate and resulted in abnormal egg development. Overexpression or downregulation of miR-34-5p and miR-305-5p through feeding significantly decreased the adult eclosion rate and caused molting defects. The 4 miRNAs, miR-let-7a, miR-315, miR-34-5p, and miR-305-5p, had important regulatory functions and insecticidal properties in egg hatching and adult eclosion. In general, these data advance our understanding of miRNAs in mite biology, which can assist future studies on insect-specific miRNA-based green pest control technology.

miR-2940-1 is involved in the circadian regulation of oviposition in Aedes albopictus

The vast majority of all global species have circadian rhythm cycles that allow them to adapt to natural environments. These regular rhythms are regulated by core clock genes and recent studies have also implicated roles for microRNAs in this regulation. Oviposition is an important circadian behavior in the reproductive cycle of insect vectors of diseases, and little is known about the rhythm or its regulation in mosquitoes. Aedes albopictus is a diurnal mosquito that transmits arboviruses and is the major cause of outbreaks of dengue fever in China. We analyzed the oviposition rhythm patterns of A. albopictus under different light/dark conditions and show that the mosquitoes have an oviposition peak between zeitgeber time 9 (ZT 9) and ZT 12. Furthermore, the antagomir-mediated knockdown of expression of the microRNA miR-2940-1 affected the oviposition rhythm of A. albopictus. These data support the conclusion that miR-2940-1 is involved in the regulation of oviposition rhythm in A. albopictus and provide a foundation for using oviposition rhythms as a new target for vector mosquito control.

Low concentrations of cyantraniliprole negatively affects the development of Spodoptera frugiperda by disruption of ecdysteroid biosynthesis and carbohydrate and lipid metabolism

In addition to the acute lethal toxicity, insecticides might affect population dynamics of insect pests by inducing life history trait changes under low concentrations, however, the underlying mechanisms remain not well understood. Here we examined systemic impacts on development and reproduction caused by low concentration exposures to cyantraniliprole in the fall armyworm (FAW), Spodoptera frugiperda, and the putative underlying mechanisms were investigated. The results showed that exposure of third-instar larvae to LC10 and LC30 of cyantraniliprole significantly extended larvae duration by 1.46 and 5.41 days, respectively. Treatment with LC30 of cyantraniliprole significantly decreased the pupae weight and pupation rate as well as the longevity, fecundity and egg hatchability of female adults. Consistently, we found that exposure of FAW to LC30 cyantraniliprole downregulated the mRNA expression of four ecdysteroid biosynthesis genes including SfNobo, SfShd, SfSpo and SfDib and one ecdysone response gene SfE75 in the larvae as well as the gene encoding vitellogenin (SfVg) in the female adults. We also found that treatment with LC30 of cyantraniliprole significantly decreased the whole body levels of glucose, trehalose, glycogen and triglyceride in the larvae. Our results indicate that low concentration of cyantraniliprole inhibited FAW development by disruption of ecdysteroid biosynthesis as well as carbohydrate and lipid metabolism, which have applied implications for the control of FAW.

Leucine aminopeptidase1 controls egg deposition and hatchability in male Aedes aegypti mosquitoes

Aedes aegypti are vectors for several arboviruses infecting hundreds of millions of people annually. Controlling mosquito populations by regulating their reproduction is a potential strategy to minimize viral transmission in the absence of effective antiviral therapies or vaccines. Here, we demonstrate that leucine aminopeptidase1 (LAP1), detected by a SWATH-MS-based proteomic screen of female spermathecae, is a crucial determinant in mosquito population expansion. Mitochondrial defects and aberrant autophagy of sperm in LAP1 mutant males (LAP1-/-), prepared using CRISPR/Cas9 system, result in a reduction of reproduction in wild-type females that mated with them. The fitness of LAP1-/- males is strong enough to efficiently transmit genetic changes to mosquito populations through a low number of hatchable offspring. Thus, LAP1-/- males represent an opportunity to suppress mosquito populations and further studies should be undertaken to characterize LAP1's suitability for gene drive usage.

Identification and Characterization of Development-Related microRNAs in the Red Flour Beetle, Tribolium castaneum

MicroRNAs (miRNAs) play important roles in insect growth and development, but they were poorly studied in insects. In this study, a total of 883 miRNAs were detected from the early embryo (EE), late larva (LL), early pupa (EP), late pupa (LP), and early adult (EA) of Tribolium castaneum by microarray assay. Further analysis identified 179 differentially expressed unique miRNAs (DEmiRNAs) during these developmental stages. Of the DEmiRNAs, 102 DEmiRNAs exhibited stage-specific expression patterns during development, including 53 specifically highly expressed miRNAs and 20 lowly expressed miRNAs in EE, 19 highly expressed miRNAs in LL, 5 weakly expressed miRNAs in EP, and 5 abundantly expressed miRNAs in EA. These miRNAs were predicted to target 747, 265, 472, 234, and 121 genes, respectively. GO enrichment analysis indicates that the targets were enriched by protein phosphorylation, calcium ion binding, sequence-specific DNA binding transcription factor activity, and cytoplasm. An RNA interference-mediated knockdown of the DEmiRNAs tca-miR-6-3p, tca-miR-9a-3p, tca-miR-9d-3p, tca-miR-11-3p, and tca-miR-13a-3p led to defects in metamorphosis and wing development of T. castaneum. This study has completed the identification and characterization of development-related miRNAs in T. castaneum, and will enable us to investigate their roles in the growth and development of insect.

miR-309a is a regulator of ovarian development in the oriental fruit fly Bactrocera dorsalis

Fecundity is arguably one of the most important life history traits, as it is closely tied to fitness. Most arthropods are recognized for their extreme reproductive capacity. For example, a single female of the oriental fruit fly Bactrocera dorsalis, a highly invasive species that is one of the most destructive agricultural pests worldwide, can lay more than 3000 eggs during its life span. The ovary is crucial for insect reproduction and its development requires further investigation at the molecular level. We report here that miR-309a is a regulator of ovarian development in B. dorsalis. Our bioinformatics and molecular studies have revealed that miR-309a binds the transcription factor pannier (GATA-binding factor A/pnr), and this activates yolk vitellogenin 2 (Vg 2) and vitellogenin receptor (VgR) advancing ovarian development. We further show that miR-309a is under the control of juvenile hormone (JH) and independent from 20-hydroxyecdysone. Thus, we identified a JH-controlled miR-309a/pnr axis that regulates Vg2 and VgR to control the ovarian development. This study has further enhanced our understanding of molecular mechanisms governing ovarian development and insect reproduction. It provides a background for identifying targets for controlling important Dipteran pests.

The ovary is a very critical organ for insect reproduction. Especially, many insect pests are famous for their large reproductive capacity. Therefore, understanding the molecular mechanisms involved in ovarian development could significantly contribute in the development of new insect pest control strategies. In this study, we report that miR-309a regulates the development of the ovary in an important dipteran pest, B. dorsalis, through a transcriptional factor, pannier (GATA-binding factor A/pnr), which in turn directly mediates the expression of yolk vitellogenin 2 (Vg 2) and vitellogenin receptor (VgR). Moreover, miR-309a is under the upstream control of juvenile hormone (JH). Here, in Dipterans, a novel JH-miR-309a-pnr-Vg-related genes regulatory pathway was found in ovarian development. This finding advances our understanding of a mechanism regulating insect ovarian development and provides new insights for potential targets to control dipteran pests through the reproductive strategy.

UVB irradiation differential regulate miRNAs expression in skin photoaging

Background

UVB irradiation can cause acute damage such as sunburn, or photoaging and melanoma, all of which are major health threats.

Objective

This study was designed to investigate the mechanism of skin photoaging induced by UVB radiation in mice through the analysis of the differential expression of miRNAs.

Methods

A UVB irradiation photoaging model was constructed. HE and Masson special stains were used to examine the modifications in the epidermis and dermis of mice. The miRNA expression profiles of the mouse skin model exposed to UVB radiation and the normal skin of mice were analyzed using miRNA-sequence analysis. GO and Pathway analysis were employed for the prediction of miRNA targets.

Results

A total of 23 miRNAs were evaluated for significantly different expressions in comparison to normal skin. Among them, 7 miRNAs were up-regulated and 16 were down-regulated in the skin with photoaging of mice exposed to UVB irradiation. The differential expression of miRNA is related to a variety of signal transduction pathways, among which mmu-miR-195a-5p and mitogen-activated protein kinase (MAPK) signal pathways are crucial. There was a significant differential expression of miRNA in the skin of normal mice in comparison with the skin with photoaging induced by UVB irradiation.

Study limitations

Due to time and energy constraints, the specific protein level verification, MAPK pathway exploration, and miR-195a-5p downstream molecular mechanism need to be further studied in the future.

Conclusions

UVB-induced skin photoaging can be diagnosed and treated using miRNA.