Supplementary Material for: Concerted Evolution of Genus-Specific Centromeric Satellite DNA in Eremias (Lacertidae, Reptilia)

Background
Tandemly repeated satellite DNA sequences are an important part of animal genomes. They are involved in chromosome interactions and the maintenance of the integral structure of the nucleus, regulation of chromatin conformation and gene expression, chromosome condensation and movement during cell division. Satellite DNAs located in the centromeric heterochromatin evolve rapidly and likely affect hybrid fertility and fitness. However, their studies are taxonomically highly biased. In lacertid lizards, satDNA has been extensively studied in the subfamily Lacertinae, but the subfamily Eremiadinae has been largely overlooked.
Results
In this work, we describe a novel 177 bp-long centromeric satDNA family EremSat177, which is present in all studied species of the genus Eremias, but not in related genera. EremSat177 is not homologous to any previously identified centromeric satellites. Using fluorescence in situ hybridization, we demonstrate its centromeric localization in E. velox and E. arguta. We also show its tandem organization and intra-genomic homogenization by in silico analysis in the genome of E. argus. The phylogenetic analysis of consensus EremSat177 sequences from 12 Eremias species demonstrates that the same monomer subfamily is the most abundant in all these species, and its evolution mainly follows the species phylogeny as revealed by the mtDNA sequences.
Conclusion
The EremSat177 represents a novel, lineage-specific centromeric satellite DNA, which role in centromere functioning should be revealed in further research.

背景
串联重复卫星DNA（tandemly repeated satellite DNA）是动物基因组的重要组成部分。它们参与染色体相互作用、细胞核整体结构的维持、染色质构象与基因表达的调控、细胞分裂过程中的染色体凝缩与移动。位于着丝粒异染色质中的卫星DNA进化迅速，且可能影响杂交后代的育性与适合度。然而，相关研究在分类学上存在显著偏差。在蜥蜴科（Lacertidae）蜥蜴中，蜥蜴亚科（Lacertinae）的卫星DNA已得到广泛研究，但麻蜥亚科（Eremiadinae）则在很大程度上被忽视了。

结果
本研究报道了一个全新的、长度为177 bp的着丝粒卫星DNA家族EremSat177，该序列存在于所有被研究的麻蜥属（Eremias）物种中，但未在近缘属中发现。EremSat177与此前已鉴定的所有着丝粒卫星DNA均无同源性。通过荧光原位杂交（fluorescence in situ hybridization, FISH）技术，我们证实其在快步麻蜥（E. velox）和密点麻蜥（E. arguta）的着丝粒区域定位。此外，通过对丽斑麻蜥（E. argus）基因组的生物信息学分析，我们揭示了该序列的串联组织形式与基因组内同质化现象。对12个麻蜥物种的EremSat177共识序列进行的系统发育分析表明，该单体型亚家族在所有受试物种中均为丰度最高的类型，且其进化历程主要遵循基于线粒体DNA（mitochondrial DNA, mtDNA）序列构建的物种系统发育关系。

结论
EremSat177代表了一类全新的、谱系特异性的着丝粒卫星DNA，其在着丝粒功能中扮演的角色有待后续研究进一步揭示。