Ecdysone-induced microRNA miR-276a-3p controls developmental growth by targeting the insulin-like receptor in Drosophila

microRNA miR-315-5p regulates developmental growth in Drosophila wings by targeting S6k

Tissue growth in Drosophila is regulated by various factors, with microRNAs (miRNAs) emerging as key players over the past decade. However, the precise roles of miRNAs in growth regulation remain incompletely understood. In this study, we explored the biological role of miR-315 in wing growth regulation. Inhibition of miR-315-5p activity using a miR-315 sponge led to an increase in wing size, whereas its overexpression resulted in reduced wing size, primarily through a decrease in wing cell size. We identified ribosomal protein kinase p-70-S6k (S6k) as a target of miR-315-5p in relation to wing growth control. Overexpression of miR-315 reduced both total S6k and phosphorylated S6k protein levels in Drosophila S2 cells and wing discs. Additionally, a luciferase reporter assay confirmed that miR-315-5p directly binds to the 3'-untranslated region of S6k. Consistently, RNAi-mediated depletion of S6k led to smaller wings, primarily due to a reduction in cell size. Notably, co-overexpression of active S6k rescued the wing defects caused by miR-315 overexpression. Overall, these findings demonstrate that miR-315 regulates wing growth by suppressing S6k expression.

miR-34-5p mediates 20E-induced autophagy in the fat body of Bombyx mori by targeting Atg1

BACKGROUND

20-Hydroxyecdysone (20E) is an important hormone that regulates insect development and metamorphosis. The fat body of insects plays a crucial role in nutrient storage and energy metabolism and is considered the exchange center for regulating insect development. The fat body undergoes remarkable transformation during insect metamorphosis and is primarily regulated by 20E. microRNAs (miRNAs) have been identified in different insects and have multiple functions in various physiological processes. However, the interaction of 20E and miRNAs in fat body regulation remains unclear.

RESULTS

We constructed six small RNA libraries using Bombyx mori fat body treated with 20E. Expression and functional analyses were conducted to identify 20E-responsive miRNAs. In total, 431 miRNAs were identified, including 389 known and 42 novel miRNAs. Differential expression analysis revealed significant expression changes in the expression of 40, 9, and 18 miRNAs at 2 h, 6 h, and 12 h after 20E treatment, respectively. The expression of 10 miRNAs was validated using quantitative real-time PCR. miR-34-5p is a highly conserved miRNA among the 10 validated miRNAs, and autophagy-related gene 1 (Atg1) was considered a target gene of miR-34-5p. The expression analysis of miR-34-5p and Atg1 exhibited an opposite expression pattern in the fat body after the 20E treatment. Dual-luciferase assay indicated that miR-34-5p could inhibit Atg1 expression by targeting a binding site in CDS region of Atg1. In larval fat body, overexpressing miR-34-5p by injecting miR-34-5p agomir suppressed the expression of Atg1 and autophagy, whereas knocking down miR-34-5p by injecting miR-34-5p antagomir induced the expression of Atg1 and autophagy. Meanwhile, Atg1 silencing by RNAi also inhibited autophagy. These results indicate that miR-34-5p participates in 20E-induced autophagy in B. mori fat body by interacting with Atg1.

CONCLUSIONS

We systematically identified and functionally characterized miRNAs associated with 20E regulation in the fat body of B. mori. miR-34-5p is involved in 20E-induced autophagy in B. mori by regulating its target gene Atg1. These results provide insight into the role of sophisticated interactions between miRNAs, 20E regulation, and autophagy in fat body remodeling and insect metamorphosis.

mir-276a Is Required for Muscle Development in Drosophila and Regulates the FGF Receptor Heartless During the Migration of Nascent Myotubes in the Testis

MicroRNAs function as post-transcriptional regulators in gene expression and control a broad range of biological processes in metazoans. The formation of multinucleated muscles is essential for locomotion, growth, and muscle repair. microRNAs have also emerged as important regulators for muscle development and function. In order to identify new microRNAs required for muscle formation, we have performed a large microRNA overexpression screen. We screened for defects during embryonic and adult muscle formation. Here, we describe the identification of mir-276a as a regulator for muscle migration during testis formation. The mir-276a overexpression phenotype in testis muscles resembles the loss-of-function phenotype of heartless. A GFP sensor assay reveals that the 3'UTR of heartless is a target of mir-276a. Furthermore, we found that mir-276a is essential for the proper development of indirect flight muscles and describe a method for determining the number of nuclei for each of the six longitudinal muscle fibers (DLMs), which are part of the indirect flight muscles.

Regulatory networks of mRNAs and miRNAs involved in the immune response of diamondback moth, Plutella xylostella to fungal infection

BACKGROUND

The entomopathogenic fungus, Isaria fumosorosea, shows promise as a biological control agent in managing the diamondback moth (DBM) Plutella xylostella, a highly destructive global pest of cruciferous vegetables. To date, the miRNA-mRNA regulatory networks underlying the immune response of DBM to I. fumosorosea infection are still poorly understood. Here, we characterize the expression profiles of miRNA and mRNA, and construct the miRNA-gene regulatory network in DBM infected with I. fumosorosea.

RESULTS

We identified 580 differentially expressed genes (DEGs) and 55 differentially expressed miRNAs (DEMs) in I. fumosorosea-infected DBM. Among these DEGs, we found 28 immunity-related genes, which mainly include pattern recognition receptors, signal modulators, and immune effectors. Integrated analysis discovered 87 negative correlation pairs between miRNA and mRNA, involving 40 DEMs and 62 DEGs in infected DBM. Additionally, 13 miRNAs and 10 corresponding mRNAs were identified as candidate miRNA-mRNA pairs for DBM immunity against fungal infection. Gene functional enrichment analysis indicated that these miRNAs could target genes associated with various pathways, such as the immune system, infectious diseases, digestive system, endocrine system, nervous system, and signal transduction. Finally, the regulatory relationships of six miRNA-mRNA pairs were validated using quantitative reverse transcription PCR.

CONCLUSIONS

For the first time, we present integrated miRNA and mRNA data to elucidate the immune response of the DBM to fungal infection. Our findings enhance the understanding of the immune response of the DBM to entomopathogenic fungi infection.

Drosophila miR-263b-5p controls wing developmental growth by targeting Akt

Tissue growth is controlled by various signaling pathways, such as the insulin/IGF-signaling (IIS) pathway. Although IIS activation is regulated by a complex regulatory network, the mechanism underlying miRNA-based regulation of the IIS pathway in Drosophila wing development remains unclear. In this study, we found that the wing size of adult flies was negatively affected by miR-263b expression. The miR-263b-mediated alteration in wing size was linked to a reduction in wing cell number. Additionally, miR-263b overexpression in Drosophila S2 cells decreased cell proliferation and increased cell death. Consequently, we identified Akt as a direct target of miR-263b-5p and found that miR-263b-mediated wing growth regulation was due to changes in Akt expression. Co-expression of Akt in miR-263b-overexpressing wings rescued the miR-263b overexpression-mediated reduction in wing growth. These results enhance our understanding of the crucial role of miRNAs in growth regulation during Drosophila wing development.

miR-276 and miR-182013-5p modulate insect metamorphosis and reproduction via dually regulating juvenile hormone acid methyltransferase

Juvenile hormone (JH) represses insect metamorphosis and stimulates reproduction. JH titers are generally low in juveniles, drop to a nadir during metamorphosis, increase after eclosion and peak in vitellogenic phase. We found that Jhamt, a rate-limiting enzyme in JH biosynthesis, mirrors JH titer patterns in the migratory locust. Knocking down Jhamt reduced JH titers, led to precocious nymphal ecdysis, metamorphosis and impaired vitellogenesis. Jhamt is negatively regulated by miR-276 and positively by miR-182013-5p. miR-276 is abundant in late nymphal but low in adults, while miR-182013-5p shows the opposite pattern. In nymphs, miR-276 binds more to Jhamt, while in adults, miR-182013-5p dominates. Functionally, miR-276 reduced Jhamt and JH levels, shortening nymphal development and inhibiting Vg expression. Conversely, miR-182013-5p increased Jhamt and JH levels, prolonging nymphal development and enhancing Vg expression. Our findings identify miR-276 and miR-182013-5p as dual regulators in JH biosynthesis, acting as "brake" and "accelerator," respectively. This study provides new insights into JH titer fluctuations and miRNA regulation in insect metamorphosis and reproduction.

MicroRNA miR-285 modulates the metamorphosis in Galeruca daurica by targeting Br-C

BACKGROUND

Galeruca daurica has become a new pest on the Inner Mongolia grasslands since an abrupt outbreak in 2009 caused serious damage. As a pupa indicator during insect metamorphosis, the early response gene of the ecdysone signaling pathway, Broad-Complex (Br-C), plays a vital role in the growth and development of insects. MicroRNAs (miRNAs) are small non-coding RNAs which mediate various biological activities, but it is unknown whether and how Br-C is regulated by miRNAs.

RESULTS

Temporal expression profiles revealed that miR-285 and Br-C basically displayed an opposite trend during larval-adult development, and Br-C was sharply up-regulated on the last day of final-instar larvae while miR-285 was significantly down-regulated. Both dual-luciferase reporter assay and miRNA-mRNA interaction assay indicated that miR-285 interacts with the coding sequence of Br-C and represses its expression. Not only overexpression but also downexpression of miR-285 led to the failure of larval to pupal to adult metamorphosis. In addition, both overexpression of miR-285 and silence of Br-C inhibited the expression of Br-C and other ecdysone signaling pathway genes, including E74, E75, ECR, FTZ-F1, and HR3. On the contrary, suppressing miR-285 obtained opposite results. Further experiments showed that 20-hydroxyecdysone down-regulated miR-285 and up-regulated Br-C and above-mentioned genes, whereas juvenile hormone alalogue (JHA) resulted in opposite effects.

CONCLUSION

Our results reveal that miR-285 is involved in mediating the metamorphosis in G. daurica by targeting Br-C in the ecdysone signaling pathway. miR-285 and its target Br-C could be as a potential target for G. daurica management. © 2024 Society of Chemical Industry.

The Biological Roles of microRNAs in Drosophila Development

Drosophila is a well-established insect model system for studying various physiological phenomena and developmental processes, with a focus on gene regulation. Drosophila development is controlled by programmed regulatory mechanisms specific to individual tissues. When key developmental processes are shared among various insects, the associated regulatory networks are believed to be conserved across insects. Thus, studies of developmental regulation in Drosophila have substantially contributed to our understanding of insect development. Over the past two decades, studies on microRNAs (miRNAs) in Drosophila have revealed their crucial regulatory roles in various developmental processes. This review focuses on the biological roles of miRNAs in specific tissues and processes associated with Drosophila development. Additionally, as a future direction, we discuss sequencing technologies that can analyze the interactions between miRNAs and their target genes, with the aim of enhancing miRNA studies in Drosophila development.