Basic characterization of avian β‐defensin genes in the Japanese quail, Coturnix japonica

In this study, we identified a cluster of 14 avian β‐defensins ( AvBD ; approximately 66 kbp) in the Japanese quail, Coturnix japonica . Except for AvBD12 ( CjAvBD12 ) and ‐ 13 , the CjAvBDs coding sequences exhibited greater than 78.0% similarity to the respective orthologous chicken AvBD genes ( GgAvBD ). The putative amino acid sequence encoded by each CjAvBD contained six cysteine residues and the GXC (X1‐2) motif considered essential for the β ‐defensin family. Each CjAvBDs also formed a sub‐group with the respective orthologous genes of various bird species in a phylogenetic tree analysis. Synteny between the CjAvBD cluster and GgAvBD cluster was confirmed. The CjAvBD cluster was mapped on the long‐arm end of chromosome 3 by linkage analysis based on single nucleotide polymorphisms (SNPs) of CjAvBD1 and CjAvBD12 (approximately 46kbp), as well as GgAvBD cluster. We also confirmed that CjAvBD1 , ‐ 4 , ‐ 5 , ‐ 9 , and ‐ 10 are transcribed in 20 tissues, including immune and digestive tissues. However, our experimental data indicated that the CjAvBD cluster lacks the AvBD3 and ‐ 7 loci, whereas the CjAvBD101α , ‐ 101β , and ‐ 101θ loci arose from gene duplication of the AvBD6 orthologous locus in the CjAvBD cluster after differentiation between Coturnix ‐ Gallus .