MiR-2b-2-5p regulates lipid metabolism and reproduction by targeting <i>CREB</i> in <i>Bactrocera dorsalis</i>

In female animals, metabolic homoeostasis and reproductive fitness are critical to population expansion. The trade-off between lipid storage and reproduction inevitably occurs. However, most studies have focused on the complex network of relationships between reproductive and metabolic physiology at the transcriptional level. In this study, we identified a microRNA, miR-2b-2-5p, in a highly invasive quarantine pest, Bactrocera dorsalis. Knockdown of miR-2b-2-5p by antagomiR microinjection impaired ovarian development, reduced fecundity, and decreased triglyceride (TAG) storage in the fat body, whereas overexpression of miR-2b-2-5p by injection of its mimic caused reproductive defects similar to knockdown but increased TAG. Bioinformatics analysis and dual luciferase assay indicated that cyclic AMP response element (CRE)-binding protein (CREB) was the target gene of miR-2b-2-5p. RNAi-mediated knockdown of CREB led to excessive lipid storage and reproductive defects. Further starvation treatment revealed that miR-2b-2-5p functions by fine-tuning CREB expression in response to dietary stimuli. These results suggest that miR-2b-2-5p acts as a monitor to regulate CREB mRNA levels in the fat body, maintaining lipid homoeostasis and keeping the reproductive system on track. Thus, our study not only provides new insights into the interaction between metabolism and reproduction at the posttranscriptional level in B. dorsalis, but also providing a potential eco-friendly control strategy (RNAi-based biopesticides targeting essential miRNAs) for this notorious agricultural pest.在雌性动物中，代谢稳态与繁殖适合度对种群扩张至关重要。脂质储存与繁殖之间不可避免地存在权衡关系。然而，当前多数研究聚焦于转录层面上生殖与代谢生理学之间的复杂调控网络。本研究在极具入侵性的检疫性害虫橘小实蝇（Bactrocera dorsalis）中鉴定出一种微小RNA（microRNA, miR-2b-2-5p）。通过拮抗miRNA（antagomiR）显微注射敲低miR-2b-2-5p的表达，会损害卵巢发育、降低繁殖力，并减少脂肪体中的甘油三酯（triglyceride, TAG）储存；而通过注射其模拟物过表达miR-2b-2-5p，则会引发与敲低实验相似的生殖缺陷，但会提升甘油三酯储存水平。生物信息学分析与双荧光素酶报告基因实验（dual luciferase assay）结果显示，cAMP应答元件（cyclic AMP response element, CRE）结合蛋白（CRE-binding protein, CREB）是miR-2b-2-5p的靶基因。通过RNA干扰（RNAi）介导敲低CREB的表达，会导致过量脂质储存与生殖缺陷。进一步的饥饿处理实验表明，miR-2b-2-5p可通过在膳食刺激下精细调控CREB的表达发挥功能。上述结果提示，miR-2b-2-5p可作为一种监控因子，在脂肪体内调节CREB的mRNA水平，维持脂质稳态并保障生殖系统正常运转。因此，本研究不仅为解析橘小实蝇中代谢与生殖在转录后层面的互作机制提供了新视角，还为这种重大农业害虫提供了一种潜在的环境友好型防控策略——以关键微小RNA为靶点的基于RNA干扰的生物农药。