Molecular and Potential Regulatory Mechanisms of Melanin Synthesis in Harmonia axyridis

• Published in: International journal of molecular sciences Vol. 21; no. 6; p. 2088
• Main Authors: Xiao, Da, Chen, Xu, Tian, Renbin, Wu, Mengmeng, Zhang, Fan, Zang, Liansheng, Harwood, James D, Wang, Su
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 18.03.2020; MDPI
• Subjects: Adults; Aromatic-L-amino-acid decarboxylase; Dihydroxyphenylalanine; dopa decarboxylase; Dopamine; dopamine melanin; Elytra; Enzymes; Epidermis; Genes; Harmonia axyridis; Hydroxylase; Insects; Larvae; Melanin; Melanization; pannier; Phenotypes; Phenotypic variations; Physiology; Pigmentation; Polymorphism; RNA-mediated interference; Studies; Transcription factors; Tyrosine; Tyrosine 3-monooxygenase; tyrosine hydroxylase; Harmonia axyridis; dopamine melanin; DOPA decarboxylase; Pannier; tyrosine hydroxylase
• ISSN: 1422-0067; 1661-6596; 1422-0067
• DOI: 10.3390/ijms21062088

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 .