Comparative Analysis of Tandem Repeats and Transposable Elements in Three Coastal Suaeda Species

In order to analyze the types, abundance, chromosomal distribution patterns, and interspecific differences of repetitive sequences in three common species of coastal Suaeda, the sequence similarity-based clustering analysis and fluorescence in situ hybridization techniques were used for the comparative analysis of their repetitive sequences. The results revealed that there were tandem repeats and transposable elements in all the three species. Among them, the telomeric sequences, 5S rDNA, and 35S rDNA were identified as the conserved tandem repeats across the three species, while the other two tandem repeats were identified as being specific to Suaeda glauca. These tandem repeats tended to be enriched in the chromosome telomeres, subtelomeres, and chromosomal arms. Furthermore, the transposable elements in the three Suaeda species were mainly composed of retrotransposons and DNA transposons. Notably, the genome of Ty3/gypsy retrotransposons were found to have a higher genomic proportion, while the Ty1/copia retrotransposons and DNA transposons were relatively less abundant. Except for the CRM lineage, which was mainly clustered in the centromeric region, most of transposable elements exhibited a dispersed distribution across the chromosomes, while some transposable elements with lower genomic abundance were not detected. According to the analysis results of repetitive sequence and chromosomal distribution, the genomic relationship between Suaeda australis and Suaeda salsa was closer than that of Suaeda glauca. These findings would provide a basis for understanding the characteristics of repetitive sequences and the evolutionary relationships among the three species of coastal Suaeda.