Identification and expression analysis of the β-defensin genes in the goat

Defensins represent a family of cysteine-rich peptides that have broad-spectrum antimicrobial activities and serve as a typical kind of effector molecule in the immunity. Ruminant species have a large number of beta-defensins in the absence of alpha- and theta-defensins. It is well-known that the genomes of sheep and cattle harbor at least 43 and 57 beta-defensin genes, respectively. However, the repertoire of the goat beta-defensin gene family has not been fully elucidated. In this study, we identified a total of 50 beta-defensins from the goat genome, including 48 functional genes and 2 pseudogenes. Cross-species genomic and evolutionary analyses showed that all of the beta-defensins in goat chromosomes 8, 13 and 23 present one-to-one orthologous relationships to their sheep and cattle counterparts, whereas some beta-defensin genes in goat chromosome 27 are goat-specific. Moreover, we observed that some duplicated genes in goat chromosome 27 may be derived from gene copy number variation, and the annotation of sheep and cattle beta-defensins appears to be incomplete in the genome. Importantly, real-time PCR analysis showed that 17 beta-defensins are expressed in the small intestine with abundant cBD1s expression. These findings significant increased our knowledge of ruminant beta-defensin and provided useful information for genetic studies, as well as providing a foundation for future research exploring the role of defensins in the immune response.