Background The dazzling phenotypic characteristics of male Indian peafowl (Pavo cristatus) are attractive both to the female of the species and to humans. However, little is known about the evolution of the phenotype and phylogeny of these birds at the whole-genome level. So far, there are no reports regarding the genetic mechanism of the formation of leucism plumage in this variant of Indian peafowl. Results A draft genome of Indian peafowl was assembled, with a genome size of 1.05 Gb (the sequencing depth is 362×), and contig and scaffold N50 were up to 6.2 and 11.4 Mb, respectively. Compared with other birds, Indian peafowl showed changes in terms of metabolism, immunity, and skeletal and feather development, which provided a novel insight into the phenotypic evolution of peafowl, such as the large body size and feather morphologies. Moreover, we determined that the phylogeny of Indian peafowl was more closely linked to turkey than chicken. Specifically, we first identified that PMEL was a potential causal gene leading to the formation of the leucism plumage variant in Indian peafowl. Conclusions This study provides an Indian peafowl genome of high quality, as well as a novel understanding of phenotypic evolution and phylogeny of Indian peafowl. These results provide a valuable reference for the study of avian genome evolution. Furthermore, the discovery of the genetic mechanism for the development of leucism plumage is both a breakthrough in the exploration of peafowl plumage and also offers clues and directions for further investigations of the avian plumage coloration and artificial breeding in peafowl.

Poultry skeletal muscle provides high quality protein for humans. Study of the genetic mechanisms during duck skeletal muscle development contribute to future duck breeding and meat production. In the current study, three breast muscle samples from Shan Ma ducks at embryonic day 13 (E13) and E19 were collected, respectively. We detected microRNA (miRNA) expression using high throughput sequencing following bioinformatic analysis. qRT-PCR validated the reliability of sequencing results. We also identified target prediction results using the luciferase reporter assay. A total of 812 known miRNAs and 279 novel miRNAs were detected in six samples; as a result, 61 up-regulated and 48 down-regulated differentially expressed miRNAs were identified between E13 and E19 (|log2 fold change| ≥ 1 and p ≤ 0.05). Enrichment analysis showed that target genes of the differentially expressed miRNAs were enriched on many muscle development-related gene ontology (GO) terms and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways, especially mitogen-activated protein kinase (MAPK) signaling pathways. An interaction network was constructed using the target genes of the differentially expressed miRNAs. These results complement the current duck miRNA database and offer several miRNA candidates for future studies of skeletal muscle development in the duck.

Ten indigenous chicken breeds were originally distributed in Jiangxi Province, China, and they define a critical component of Chinese chicken genetic resources. We have investigated the population genetics of seven Jiangxi chicken breeds using 600K chicken BeadChip SNP data. To provide a genome-wide perspective for the population structure of all 10 Jiangxi chicken breeds, we herein genotyped 78 additional individuals from the seven breeds and 63 chickens from three uninvestigated breeds-Yugan Black (YG), Nancheng Black (NC) and Wanzai Yellow using 55K chicken SNP arrays. We then explored merged data of 17 101 SNPs from 235 individuals to infer the population structure of the 10 breeds. We showed that NC and YG are two regional populations of the same breed, as individuals from the two populations clustered together to form a branch separate from the other breeds in the neighbor-joining tree, they always grouped together in multidimensional principal component analyses and they displayed an identical pattern of ancestral lineage composition. Hence, NC and YG should be considered a single breed in the state-supported conservation scheme. Moreover, we conducted a genome scan for signatures of selection for black plumage. BAYESCAN and HAPFLK analyses of two contrasting groups (three blackfeathered breeds vs. six non-black-feathered breeds) consistently detected 25 putative regions under selection. Nine pigmentation-associated genes (DCT, SLC24A5, SLC30A4, MYO5A, CYP19A1, NADK2, SLC45A2, GNAQ and DCP2) reside within these regions, and these genes are interesting candidates for black plumage and provide a starting point for further identification of causative mutations for black feathers in chicken.

Bird feathers are the product of interactions between natural and artificial selection. Feather-related traits are important for chicken selection and breeding. Frizzle feather is characterized by the abnormally development of feathers in chickens. In the current study, frizzle feather characteristics were observed in a local breed called Xiushui Yellow Chicken in Jiangxi, China. To determine the molecular mechanisms that underlie frizzle feather in Xiushui Yellow Chicken, four populations of three breeds (Xiushui Yellow Chicken with frizzle feathers, Xiushui Yellow Chicken with normal feathers, Guangfeng White-Ear Yellow Chicken, and Ningdu Yellow Chicken) were selected for whole-genome resequencing. Using a comparative genome strategy and genome-wide association study, a missense mutation (g.5281494A>G) and a 15-bp deletion (g.5285437-5285451delGATGCCGGCAGGACG) in KRT75L4 were identified as candidate mutations associated with frizzle feather in Xiushui Yellow Chicken. Based on genotyping performed in a large Xiushui Yellow Chicken population, the g.5285437-5285451delGATGCCGGCAGGACG mutation in KRT75L4 was confirmed as the putative causative mutation of frizzle feather. These results deepen the understanding of the molecular mechanisms responsible for frizzle feather, as well as facilitating the molecular detection and selection of the feather phenotype in Xiushui Yellow Chickens.

The aim of this study was to compare the meat quality and evaluate the chemical composition of Chinese Ningdu yellow chicken of different weights once they have reached market age. Thirty hens at the day of age 118 were selected and divided into three groups according to their weight: light weight (1288.00 AE 69.78 g, n = 10), medium weight (1407.17 AE 39.40 g, n = 10), heavy weight (1581.6 AE 46.59 g, n = 10), and the differences in weight among these three groups are significant. Biochemical, histological, and metabonomic approaches were used to obtain index values of meat quality and chemical composition. Compared with meat from lighter chickens, muscle fiber density was significantly lower in heavier chickens, and meat pH was positively correlated with chicken weight. Though the amount of all measured amino acids were not different among three weight groups of chicken, the levels of several kinds of fatty acids exhibited significant differences or correlations, including linolenic acid, arachidonic acid, myristic acid, oleic acid, and docosahexaenoic acid (DHA). These results contribute to help customers choose the optimal chicken weight depending upon the food to be cooked.