# MicroRNA Novel-m0027-3p Negatively Regulates Jhamt Gene and Affects Juvenile Hormone Biosynthesis in Apis mellifera Larvae

## TL;DR

A new microRNA in honeybees, novel-m0027-3p, was found to control juvenile hormone production by targeting a key enzyme gene, affecting larval development.

## Contribution

The study identifies novel-m0027-3p as a regulator of Jhamt, linking miRNA activity to juvenile hormone biosynthesis in honeybees.

## Key findings

- Novel-m0027-3p suppresses the expression of the JH biosynthesis gene AmJhamt in honeybee larvae.
- Larvae with increased novel-m0027-3p had lower juvenile hormone levels and reduced downstream gene activity.
- Inhibiting novel-m0027-3p increased juvenile hormone titers and upregulated signaling genes.

## Abstract

Honeybees play a crucial role in sustaining agricultural production and maintaining ecosystem balance. MicroRNAs (miRNAs) are involved in bee development and caste differentiation by regulating gene transcription and translation. Our findings indicate that hormones act as a key bridge in the miRNA-mediated regulation of honeybee physiology. Specifically, miRNA novel-m0027-3p can directly target juvenile hormone (JH) acid methyl transferase (Jhamt), a key gene involved in JH synthesis, thereby modulating JH titers and signaling pathways during larval development. Our study provides insights into how miRNAs regulate hormone pathways to affect honey bee development.

Juvenile hormone (JH) is a key regulator of larval development in honeybees. Its biosynthesis involves multiple enzymatic steps and is modulated by a complex regulatory network that includes microRNAs (miRNAs). Juvenile hormone acid methyltransferase (JHAMT) catalyzes the final step in JH synthesis. This study demonstrates that the miRNA novel-m0027-3p negatively regulates the expression of the Jhamt gene in Apis mellifera larvae (AmJhamt), thereby mediating JH biosynthesis. Bioinformatics predictions indicate that novel-m0027-3p potentially targets six hormone-related genes (22 mRNAs), including AmJhamt. Dual-luciferase reporter assays and mimics/inhibitor-miRNA feeding confirmed that novel-m0027-3p significantly suppresses the expression of the target gene AmJhamt. In vivo experiments showed that larvae fed with the mimics of novel-m0027-3p exhibited decreased JH titers and significantly downregulated expression of JH signaling downstream genes AmHex70b and AmKr-h1. Conversely, larvae fed with the inhibitors of novel-m0027-3p displayed significantly elevated JH titers and markedly upregulated expression of AmHex70b and AmKr-h1. Our findings provide experimental evidence for the coupling between miRNAs and hormonal pathways in honeybees.