Recent advances in avian melanogenesis have pinpointed multiple genetic loci associated with color polymorphisms, predominantly in the plumage of chickens, quails, and pigeons. However, the genetic basis of melaninization in parrot plumage remains elusive. Previously, we showed that mutations in the melanosomal ion-transporter SLC45A2 lead to a complete loss of blue structural color in green parrot feathers, leaving only yellow psittacofulvin. Yet, several color morphs involving partial or complete melanin reduction are common in captive-bred parrots that have not been studied. To bridge this gap, we investigated two new color morphs of parrot plumage: non-sex-linked recessive lutino (NSL), which entirely inhibits blue structural coloration, and the sex-linked recessive cinnamon, which reduces the intensity of blue structural coloration. Our genotypic analysis revealed that tyrosinase (TYR) variants are responsible for the NSL phenotype in Fischer's lovebird and green-cheeked parakeet, while tyrosinase related protein 1 (TYRP1) variants are associated with the cinnamon phenotype in the rose-ringed parakeet. When transfected into HEK293T cells, the candidate substitutions significantly affected tyrosinase enzymatic activity. This study underscores tyrosinase and related enzymes' role in parrot feather coloration, enhancing our understanding of avian melanogenesis as well as the conserved functions of melanogenic components across different species.

• Keywords
• TYR, TYRP1, eumelanin, feather, parrot,
• MeSH
• Phenotype MeSH
• Humans MeSH
• Melanins metabolism   MeSH
• Oxidoreductases * metabolism   genetics   MeSH
• Parrots * genetics   metabolism   MeSH
• Feathers * enzymology   metabolism   MeSH
• Pigmentation * genetics   MeSH
• Avian Proteins * metabolism   genetics   MeSH
• Monophenol Monooxygenase * metabolism   genetics   MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Male MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Melanins MeSH
• Oxidoreductases * MeSH
• Avian Proteins * MeSH
• Monophenol Monooxygenase * MeSH
• tyrosinase-related protein-1 MeSH Browser

Polyketide synthases (PKSs) are crucial multidomain enzymes in diverse natural product biosynthesis. Parrots use a type I PKS to produce a unique pigment called psittacofulvin in their feathers. In domesticated budgerigars and lovebirds, the same amino acid substitution (R644W) within malonyl/acetyltransferase (MAT) domain of this enzyme has been shown to cause the blue phenotype with no psittacofulvin pigmentation, proposing a strong evolutionary constraint on the mechanism. Here, we identified seven previously unreported variants in PKS associated with defective psittacofulvin production in four diverse species, including three nonsense mutations. Intriguingly, three of the remaining nonsynonymous substitutions reside within the ketoacyl synthase (KS) domain, whereas one at MAT domain. The heterologous expression of these PKS variants in yeast confirmed complete or partial loss of psittacofulvin production. These findings establish PKS as a functionally conserved key-enzyme determining psittacofulvin-based hues among diverse parrots, highlighting multiple conserved domains essential for the PKS function.

• MeSH
• Pigments, Biological * biosynthesis   MeSH
• Mutation * MeSH
• Parrots * genetics   metabolism   MeSH
• Feathers metabolism   MeSH
• Pigmentation genetics   MeSH
• Polyketide Synthases * genetics   metabolism   MeSH
• Animals MeSH
• Check Tag
• Animals MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Pigments, Biological * MeSH
• Polyketide Synthases * MeSH