Xu Xiaoqin, Jian Yi, Huang Lijing, Luo Wei, Wu Bangyuan, Feng Shaohua, Zhou Caiquan, Zhang Long
Key Laboratory of Southwest China Wildlife Resources Conservation, Ministry of Education, China West Normal University, Nanchong, 637000, P. R. China.
Sichuan Wildlife Rehabilitation and Breeding Research Center, China West Normal University, Nanchong, 637009, P. R. China.
BMC Genomics. 2025 Mar 3;26(1):211. doi: 10.1186/s12864-025-11390-7.
Avian β-defensins (AvBDs) represent a key family of antimicrobial host defense peptides in birds. Accumulating evidence suggests that the evolutionary trajectory of β-defensin genes is specific to the gene, timescale, and species involved, implying that species-specific ecological and life-history differences drive divergent selective pressures on these genes. However, their evolutionary dynamics, particularly the interactions with ecological factors and life-history traits, remain insufficiently explored.
Through a comprehensive survey of 25 species spanning all major clades of Galliformes, 354 AvBD genes were identified. Comparative sequence analysis, genomic organization, and phylogenetic studies collectively reveal significant evolutionary diversification characterized by gene duplication, pseudogenization, and gene loss across these species. Notably, chicken AvBD3 exhibits significant differences in its coding regions, while AvBD6 and AvBD7 appear to have copy number variations, with species-specific paralogs of AvBD6 being especially prominent. Moreover, positive selection was more frequently observed in recently diverged gene lineages compared to ancestral ones. Using 70 samples from eight galliform species, the study further identified the prevalence of species-specific amino acid alleles. Phylogenetic comparative analysis demonstrated that the evolution of nine AvBD genes (AvBD2, -4, -5, -8, -9, -10, -11, -12, and -14) is significantly associated with specific ecological factors and life-history characteristics. Additionally, the evolutionary rates of these genes showed distinct relationship with inferred infection risk, likely reflecting the multifunctionality of β-defensins and potential trade-offs between immune defense and other biological functions.
This cross-species identification and systematic evolutionary analysis of AvBDs in Galliformes deepen our understanding of the co-evolution of host defense peptides, offering valuable insights into their natural biology and evolution, and paving the way for future applications as alternatives to traditional antibiotics.
禽β-防御素（AvBDs）是鸟类抗菌宿主防御肽的一个关键家族。越来越多的证据表明，β-防御素基因的进化轨迹因所涉及的基因、时间尺度和物种而异，这意味着物种特异性的生态和生活史差异对这些基因施加了不同的选择压力。然而，它们的进化动态，特别是与生态因素和生活史特征的相互作用，仍未得到充分探索。
通过对鸡形目所有主要分支的25个物种进行全面调查，共鉴定出354个AvBD基因。比较序列分析、基因组组织和系统发育研究共同揭示了这些物种中以基因复制、假基因化和基因丢失为特征的显著进化多样化。值得注意的是，鸡的AvBD3在其编码区域表现出显著差异，而AvBD6和AvBD7似乎存在拷贝数变异，其中AvBD6的物种特异性旁系同源物尤为突出。此外，与祖先基因谱系相比，在最近分化的基因谱系中更频繁地观察到正选择。该研究使用来自8个鸡形目物种的70个样本，进一步确定了物种特异性氨基酸等位基因的普遍性。系统发育比较分析表明，9个AvBD基因（AvBD2、-4、-5、-8、-9、-10、-11、-12和-14）的进化与特定的生态因素和生活史特征显著相关。此外，这些基因的进化速率与推断的感染风险呈现出明显的关系，这可能反映了β-防御素的多功能性以及免疫防御与其他生物学功能之间的潜在权衡。
对鸡形目AvBDs进行的这种跨物种鉴定和系统进化分析加深了我们对宿主防御肽共同进化的理解，为它们的自然生物学和进化提供了有价值的见解，并为未来作为传统抗生素替代品的应用铺平了道路。
