Selection signatures in melanocortin-1 receptor gene of turkeys (Meleagris gallopavo) raised in hot humid tropics

Abstract

Feather colours are used by avian species for defense, adaptation and signaling. Melanocortin-1 receptor (MC1R) gene is one of the genes responsible for feather colour. This study identified selection signatures in MC1R gene of Nigerian indigenous turkeys (NIT) using British United turkeys (BUT) as control breed to investigate the evolutionary processes that have shaped NIT with various feather colours. Complete MC1R gene of 146 NIT (76 males and 70 females) and 32 BUT (18 males and 14 females) were sequenced. Transition/transversion and codon usage biases were predicted using MEGA v6 software. The selective force acting on the gene was predicted using HyPhy software. The FST values were estimated using Arlequin v3.5. The highest transition/transversion bias was predicted for white BUT (1.00) while the lowest was predicted for black NIT (0.50). Negative dN-dS values, indicative of purifying selection, were observed in MC1R gene of all the turkeys. The highest pairwise FST was observed between the MC1R gene of white BUT and black NIT while the least was observed between lavender NIT and white NIT. No recombination event was observed in black NIT and white BUT. The relative synonymous codon usage was the same among different colours for some codons. Presence of purifying selection in MC1R gene of all the turkeys with different feather colours confirms that the gene plays role in many biological processes such as feather colouration, behaviour, pain perception, immunity, growth and adaptation. The results also suggested that the genetic mechanisms generating different feather colours in turkeys are conserved.

Keywords: Codon usage; Purifying selection; Recombination; Transition; Transversion.