The horticulture and urban entomology team has made achievements in the study of the regulation mechanism of metabolic homeostasis in the orange small fruit fly.

Nanhu News Network News (Correspondent Xie Junfei Zhang Zhenyu) On October 5, the research team of Professor Zhang Hongyu of our university published a report entitled "miR-275/305 cluster is essential for maintaining energy metabolic homeostasis by the insulin signaling pathway in" in the well-known journal PLoS Genetics Bactrocera dorsalis's article for the first time confirmed in the orange fruit fly that microRNAs (miR-275/305 clusters) are involved in the steady-state regulation of energy metabolism, and the research results have important scientific significance
for understanding the physiological regulation of insect metabolism.

As an important environmental limiting factor, dietary nutrition is essential
for insect growth, development and reproduction.
In most Diptera, feathered adults must ingest a certain amount of protein to reach sexual maturity and reproduce
.
In addition, organisms need to constantly adjust the metabolic state between tissues and organs to adapt to fluctuations in nutrition, precise control of metabolic homeostasis is critical for cell differentiation and tissue integrity, metabolic disorders can lead to serious physiological diseases such as obesity and insulin resistance
.
However, the molecular mechanisms that insects use to adjust their metabolism in response to different nutrient changes are still poorly
understood.

The study first identified the effect of eating yeast on the metabolism of adult orange flies (elevated triglycerides, glycogen and total sugar content).

The latest research has found that diet can reshape the miRNA expression profile, and further through RNAi interference miRNA biosynthesis pathway genes found that interference with AGO1 and DCR1 can also affect the metabolic state of adult worms, indicating that dietary yeast may affect the metabolic state
of orange fruit flies through miRNA.
A total of 19 differentially expressed miRNAs were identified by small RNA high-throughput sequencing
.
Among them, the evolutionarily conserved miR-275/305 cluster showed a positive synergistic response in response to yeast food stimulation, and was highly expressed
in fat-rich tissues such as fat body and intestine of orange fruit fly.
Using CRISPR/Cas9 gene editing technology, knockout of miR-275 and miR-305 significantly reduced triglyceride and glycogen content, while total sugar content increased significantly, and impaired the ability of orange fruit flies to fly (Figure 1).

Figure 1.
Mutations miR-275 and miR-305 affect adult energy metabolism

In order to further explore the mechanism of action of miR-275 and miR-305, the authors used two omics association analysis to screen target genes in the whole gene range, and then used microinjection, double luciferase detection, RNA co-precipitation and in situ hybridization to finally confirm that miR-275 and miR-305 acted on the 3'UTR region of SLC2A1 and GLIS2 to inhibit their expression
。 Functional analysis showed that SLC2A1 and GLIS2 were involved in carbon degradation and lipid metabolism processes, respectively, and that by interfering with target genes through RNAi, the metabolic phenotypes
caused by the inhibition of miR-275 and miR-305 could be partially rescued.
Further studies found that injection of exogenous insulin significantly promoted the transcription of miR-275/305 clusters and inhibited the expression of SLC2A1/GLIS2, while interfering with the insulin receptor substrate IRS showed the opposite trend
.
Interfering with the TOR pathway can also affect the transcription
of target genes.
These results suggest that the metabolic network mediated by the miR-275/305 cluster is regulated
by the insulin signaling pathway.

Based on the above conclusions, the authors propose a network model of miR-275/305 clusters regulating energy metabolism homeostasis (Figure 2
).
After ingestion of dietary yeast, the activated insulin signaling pathway promotes the transcription of miR-275/305 clusters, which inhibit transcription after binding to the target gene SLC2A1/GLIS2, thereby ensuring normal metabolic physiology, and the TOR pathway can also independently regulate target genes without affecting the transcription
of miRNAs.
Under yeast deprivation conditions, TOR and insulin signaling pathway activity is inhibited, miRNA transcription decreases, and miRNA-mediated inhibition weakens, manifested by enhanced SLC2A1/GLIS2 transcription to maintain the supply
of energy required for basic metabolism.

Figure 2.
The miR-275/305 cluster maintains the homeostasis of energy metabolism in orange flies through the insulin signaling pathway

Xie Junfei, doctoral student of Huazhong Agricultural University, is the first author of the paper, Professor Zhang Hongyu and Professor Li Xiaoxue are the co-corresponding authors, and the doctoral students Zheng Wenping and Cai Chaohui and graduate students Chen Hao are involved in some of the research work
.
This research was supported
by the National Key R&D Program (2019YFD1002100) and the National Modern Agricultural Industry Technology System (CARS-26).

Professor Zhang Hongyu's team has long been committed to the research of horticultural and urban pest catastrophic laws and green prevention and control, invasive organisms and biosafety, and has made a series of research progresses, some of which have been in Nature Communications, ISME J, PLoS Pathogens, Cells, Frontiers in Microbiology, Evolutionary Applications, Insect Mol Biol and other high-level journals published
.

English Abstract:

Increasing evidence indicates that miRNAs play crucial regulatory roles in various physiological processes of insects, including systemic metabolism.
However, the molecular mechanisms of how specific miRNAs regulate energy metabolic homeostasis remain largely unknown.
In the present study, we found that an evolutionarily conserved miR-275/305 cluster was essential for maintaining energy metabolic homeostasis in response to dietary yeast stimulation in Bactrocera dorsalis.
Depletion of miR-275 and miR-305 by the CRISPR/Cas9 system significantly reduced triglyceride and glycogen contents, elevated total sugar levels, and impaired flight capacity.
Combined in vivo and in vitro experiments, we demonstrated that miR-275 and miR-305 can bind to the 3’UTR regions of SLC2A1 and GLIS2 to repress their expression, respectively.
RNAi-mediated knockdown of these two genes partially rescued metabolic phenotypes caused by inhibiting miR-275 and miR-305.
Furthermore, we further illustrated that the miR-275/305 cluster acting as a regulator of the metabolic axis was controlled by the insulin signaling pathway.
In conclusion, our work combined genetic and physiological approaches to clarify the molecular mechanism of metabolic homeostasis in response to different dietary stimulations and provided a reference for deciphering the potential targets of physiologically important miRNAs in a non-model organism.

Original link:

https://journals.
plos.
org/plosgenetics/article?id=10.
1371/journal.
pgen.
1010418

Reviewed by: Zhang Hongyu