As a classical molecular marker, microsatellite (simple sequence repeat, SSR) has been widely used in the study of genetics and evolution of mammals. However, there are widespread problems about lack of comparative analysis and low quality of genomic data. Based on high-quality chromosome-level genomes, we compared the SSR distribution patterns of 81 mammals species belonging to 13 orders in evolution landscape. In this study, the number of SSRs decreased with the increase of repetition times, and the terminal of exon/intron were enrichment areas of SSRs. We also found that the proportion and dominant repeat units of each type of P-SSR varied among mammalian branches, which could become the evolutionary dynamics for them to adapt to diverse environmental pressures. In particular, the phylogenetic PCA results demonstrated the particularity of some mammals (Tachyglossus aculeatus and Ornithorhynchus anatinus) in evolutionary status, which was consistent with morphological cognition. Meanwhile, there were significant differences in the GC content of each category of P-SSR across mammalian taxa. Besides, the CVs (coefficient of variations) of the RCNs of trinucleotide and hexanucleotide P-SSRs were at a low level in the exon regions, while the dinucleotide or tetranucleotide P-SSRs were at a high level. Furthermore, the results of functional annotation showed that signal transduction played a pivotal role in mammalian biological activities. In conclusion, our research will help to improve the characteristic information of mammalian SSRs and explore their evolutionary background.
Keywords: Chromosome-level genome; Comparative analysis; Distribution pattern; Functional annotation; Mammals; Microsatellite.
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