Nuclear Receptor Hepatocyte Nuclear Factor (HNF4) Controls Reproduction and Survival in Cotton Aphids by Regulating Lipid Metabolism

Nuclear receptors are a family of ligand-dependent transcription factors that regulate the development, reproduction, survival, and immune responses in insects. However, the structural, biological, and molecular functions of hepatocyte nuclear factor 4 (HNF4) in aphids remain unknown. Aphids are small agricultural pests that directly affect crops due to their rapid reproductive ability, which is influenced by environmental conditions such as temperature, humidity, and photoperiod. In this study, we cloned full-length cDNA encoding HNF4 from the cotton aphid <i>Aphis gossypii</i> (<i>A. gossypii</i>, Hemiptera: Aphididae) (<i>AgHNF4</i>) and investigated its role in regulating lipid metabolic gene expression, aphid survival, and reproduction. Phylogenetic analysis revealed that <i>AgHNF4</i> shares an evolutionary lineage with other hemipteran insects. The ligand binding domain region of <i>AgHNF4</i> showed significance in nuclear localization and transcriptional activity. The expression pattern of <i>AgHNF4</i> was detected in the stages of the aphid life cycle, with notable expression during the 2nd instar, 4th instar, and adult stages. Furthermore, to understand the role of HNF4 in regulating lipid metabolic genes involved in fatty acid synthesis and transport, HNF4-silenced <i>A. gossypii</i> individuals were analyzed. The results showed downregulation of lipid metabolic genes and reduced offspring production and survival rates. Therefore, <i>A. gossypii</i> HNF4 serves as a potential target for regulating lipid metabolism, and targeting HNF4 expression could offer a promising approach to aphid pest control.