Li Junyan, Zhao Xiaochao, Xu Pengwei, Lai Juan, Gong Gaowa, Wang Penglong, Zhang Yanni, Chen Xuerou, Guo Fang, Wang Xiaomin, Liu Yongfeng, Luo Xiaoping
Key Laboratory of Grass-Feeding Livestock Healthy Breeding and Livestock Product Quality Control, Veterinary Research Institute, Inner Mongolia Academy of Agricultural and Animal Husbandry Sciences, Hohhot, 010031, China.
GeneMind Biosciences Company Limited, Shenzhen, 518001, China.
BMC Genomics. 2025 Sep 1;26(1):793. doi: 10.1186/s12864-025-11980-5.
The nematode superfamily Strongyloidea represents a prevalent group of gastrointestinal parasites in ruminants and livestock, posing substantial veterinary and economic burdens worldwide. Here we present the first mitochondrial genomic investigation for reconstructing Strongyloidea phylogeny and investigating niche-specific selection dynamics across gastrointestinal habitats (abomasum, small intestine, and large intestine). This study presents a preliminary exploration of the evolutionary adaptations of these agriculturally relevant parasites through comprehensive mitogenomic analysis.
Phylogenomic reconstruction revealed strong anatomical clustering with high nodal support. Comparative synteny analyses revealed conserved mitogenome architectures across Strongyloidea species, characterized by pronounced AT-richness. Codon usage patterns showed high consistency in Strongyloide (94% A/U-ending preferred codons), with ENC-plot and neutrality analyses confirming natural selection as the dominant driver. Pervasive purifying selection was observed, but abomasal species showed higher ω values than intestinal counterparts, particularly in ND4. In addition, positive selection was detected exclusively in CYTB within the small intestinal lineage. RELAX analysis identified differential selection signals among the three branches, with significant relaxation observed in ND5 and ND6 genes in the abomasal species. Amino acid polymorphism analyses revealed higher sequence variation in ND genes compared to the highly conserved COX genes.
Our findings demonstrated niche-associated evolutionary trajectories between abomasal and intestinal Strongyloidea branches, reflected in both phylogenetic patterns and molecular evolution rates. The mitogenomic framework established here provided a foundation for future studies integrating expanded datasets, genomic data, and microenvironmental parameters to elucidate precise niche adaptation mechanisms in these economically important parasites.
圆线总科线虫是反刍动物和家畜中常见的一类胃肠道寄生虫，在全球范围内造成了巨大的兽医和经济负担。在此，我们首次进行线粒体基因组研究，以重建圆线总科的系统发育，并研究胃肠道不同生境（皱胃、小肠和大肠）中特定生态位的选择动态。本研究通过全面的线粒体基因组分析，对这些与农业相关的寄生虫的进化适应性进行了初步探索。
系统发育基因组重建显示出强烈的解剖学聚类，节点支持率高。比较共线性分析揭示了圆线总科物种间保守的线粒体基因组结构，其特征是富含AT。密码子使用模式在圆线总科中显示出高度一致性（94%的首选密码子以A/U结尾），ENC图和中性分析证实自然选择是主要驱动力。观察到普遍的纯化选择，但皱胃物种的ω值高于肠道物种，特别是在ND4中。此外，仅在小肠谱系的CYTB中检测到正选择。RELAX分析确定了三个分支之间的差异选择信号，在皱胃物种的ND5和ND6基因中观察到显著的放松。氨基酸多态性分析显示，与高度保守的COX基因相比，ND基因的序列变异更高。
我们的研究结果表明，皱胃和肠道圆线总科分支之间存在与生态位相关的进化轨迹，这在系统发育模式和分子进化速率中都有体现。这里建立的线粒体基因组框架为未来整合扩展数据集、基因组数据和微环境参数的研究提供了基础，以阐明这些经济上重要的寄生虫精确的生态位适应机制。
