Molecular and Potential Regulatory Mechanisms of Melanin Synthesis in .

Melanization is a common phenomenon in insects, and melanin synthesis is a conserved physiological process that occurs in epidermal cells. Moreover, a comprehensive understanding of the mechanisms of melanin synthesis influencing insect pigmentation are well-suited for investigating phenotype variation. The Asian multi-colored (Harlequin) ladybird beetle, , exhibits intraspecific polymorphism based on relative levels of melanization. However, the specific characteristics of melanin synthesis in remains elusive. In this study, we performed gene-silencing analysis of the pivotal inverting enzyme, tyrosine hydroxylase (TH), and DOPA decarboxylase (DDC) in the tyrosine metabolism pathway to investigate the molecular and regulatory mechanism of melanin synthesis in . Using RNAi of and genes in fourth instar larvae, we demonstrated that dopamine melanin was the primary contributor to the overall body melanization of . Furthermore, our study provides the first conclusive evidence that dopamine serves as a melanin precursor for synthesis in the early pupal stage. According to transcription factor , which is essential for the formation of melanic color on the elytra in , we further demonstrated that suppression of can significantly decrease expression levels of and . These results in their entirety lead to the conclusion that transcription factor can regulate dopamine melanin synthesis in the dorsal elytral epidermis of .