Transcriptome Analysis Reveals Genes Associated With Sexual Dichromatism of Head Feather Color in Mallard.

Jiwen Wang,Lei Wang,Yisi Liu,Shengchao Ma,Yang Xi,Chunchun Han,Qian Xu,Hehe Liu,Jianmei Wang,Jiwei Hu,Lili Bai,Liang Li

doi:10.3389/fgene.2021.627974

Abstract

Sexual dimorphism of feather color is typical in mallards, in which drakes exhibit green head feathers, while females show dull head feather color. We showed that more melanosomes deposited in the males’ head’s feather barbules than females and further form a two-dimensional hexagonal lattice, which conferred the green feather coloration of drakes. Additionally, transcriptome analysis revealed that some essential melanin biosynthesis genes were highly expressed in feather follicles during the development of green feathers, contributing to melanin deposition. We further identified 18 candidate differentially expressed genes, which may affect the sharp color differences between the males’ head feathers, back feathers, and the females’ head feathers. TYR and TYRP1 genes are associated with melanin biosynthesis directly. Their expressions in the males’ head feather follicles were significantly higher than those in the back feather follicles and females’ head feather follicles. Most clearly, the expression of TYRP1 was 256 and 32 times higher in the head follicles of males than in those of the female head and the male back, respectively. Hence, TYR and TYRP1 are probably the most critical candidate genes in DEGs. They may affect the sexual dimorphism of head feather color by cis-regulation of some transcription factors and the Z-chromosome dosage effect.

Highlights

Plumage color differences between males and females are common in most avian species, such as Anna’s hummingbird, chicken, Japanese quail, mallard, turkey, and zebra finch (Zuk et al, 1990; Collins and Cate, 1996; Zann 1996)
We further revealed the underlying genes that affect the sexual dimorphism of feather color in mallards
More melanosomes are deposited in the males’ head’s feather barbules than females, which may cause the sexual dimorphism of head feather color in mallards directly

Summary

Introduction

Plumage color differences between males and females are common in most avian species, such as Anna’s hummingbird, chicken, Japanese quail, mallard, turkey, and zebra finch (Zuk et al, 1990; Collins and Cate, 1996; Zann 1996). The nuptial plumage of adult males is beautiful and colorful, but the plumage color of females is dull. These characteristics are known as sexual dimorphism in avian species (Andersson 1994). In the long process of sexual selection, the male’s nuptial feathers give the carrier a mating advantage (Slagsvold and Lifjeld 1992). Models of sexual selection have suggested that the feather color characteristics of males are flexible, reflecting the viability and body condition of the carrier (Zahavi 1975; Andersson 1986; Grafen 1990)

Methods

Results

Discussion

Conclusion