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• This study assembled and annotated four new plastomes from the Telephium clade. • Monophyletic Telephium clade further formed Hylotelephium and Rhodiola subclade. • No positive selection gene was observed but 19 genes had positive selection sites. • Codon usage was biased, shaped by natural selection, mutations and other factors. • 34 taxon-specific codon aversion motifs were identified from 49 plastid genes. The Telephium clade of the Crassulaceae family contains many medicinal, ornamental, and ecologically restorative plants. However, the phylogenetic relationships within the clade remain debated, and comprehensive analyses of codon usage and selection pressure in Telephium plastomes are limited. In this study, we assembled and annotated four plastomes and performed extensive analyses. The plastomes exhibited a typical quadripartite structure and high conservation. The lengths ranged from 151,357 bp to 151,641 bp with 134 genes identified. The GC content was the highest within IR, followed by LSC, and lowest in the SSC region. Meanwhile, a unique inversion was observed within the LSC region of Meterostachys sikokianus. Polymorphisms analysis revealed minimum nucleotide diversity in the IR regions, with over ten highly polymorphic regions identified. Phylogenetically, two subclades formed within the monophyletic Telephium clade, with Umbilicus as the sister group to the remaining Hylotelephium subclade members. Notably, no significant positive selection was found among the 79 plastid genes, which showed varying evolutionary patterns. However, 19 genes contained codons under positive selection. The specific functions of these sites require further investigation. Synonymous codon usage was biased and conserved across the tested plastomes, shaped by natural selection, mutations and other factors of varying influence. We also identified 34 taxon-specific codon aversion motifs from 49 plastid genes. Our plastomic analyses elucidate phylogenetic relationships and evolutionary patterns in this medicinal clade, providing a foundation for further research on these ecologically and pharmaceutically important plants. [ABSTRACT FROM AUTHOR]

Taxa of Buchnera aphidicola (hereafter " Buchnera ") are mutualistic intracellular symbionts of aphids, known for their remarkable biological traits such as genome reduction, strand compositional asymmetry, and symbiont-host coevolution. With the growing availability of genomic data, we performed a comprehensive analysis of 103 genomes of Buchnera strains from 12 host subfamilies, focusing on the genomic characterizations, codon usage patterns, and phylogenetic implications. Our findings revealed consistent features among all genomes, including small genome sizes, low GC contents, and gene losses. We also identified strong strand compositional asymmetries in all strains at the genome level. Further investigation suggested that mutation pressure may have played a crucial role in shaping codon usage of Buchnera. Moreover, the genomic asymmetries were reflected in asymmetric codon usage preferences within chromosomal genes. Notably, the levels of these asymmetries were varied among strains and were significantly influenced by the degrees of genome shrinkages. Lastly, our phylogenetic analyses presented an alternative topology of Aphididae, based on the Buchnera symbionts, providing robust confirmation of the paraphylies of Eriosomatinae, and Macrosiphini. Our objectives are to further understand the strand compositional asymmetry and codon usage bias of Buchnera taxa, and provide new perspectives for phylogenetic studies of Aphididae. [ABSTRACT FROM AUTHOR]

Taxa of Buchnera aphidicola (hereafter " Buchnera ") are mutualistic intracellular symbionts of aphids, known for their remarkable biological traits such as genome reduction, strand compositional asymmetry, and symbiont-host coevolution. With the growing availability of genomic data, we performed a comprehensive analysis of 103 genomes of Buchnera strains from 12 host subfamilies, focusing on the genomic characterizations, codon usage patterns, and phylogenetic implications. Our findings revealed consistent features among all genomes, including small genome sizes, low GC contents, and gene losses. We also identified strong strand compositional asymmetries in all strains at the genome level. Further investigation suggested that mutation pressure may have played a crucial role in shaping codon usage of Buchnera. Moreover, the genomic asymmetries were reflected in asymmetric codon usage preferences within chromosomal genes. Notably, the levels of these asymmetries were varied among strains and were significantly influenced by the degrees of genome shrinkages. Lastly, our phylogenetic analyses presented an alternative topology of Aphididae, based on the Buchnera symbionts, providing robust confirmation of the paraphylies of Eriosomatinae, and Macrosiphini. Our objectives are to further understand the strand compositional asymmetry and codon usage bias of Buchnera taxa, and provide new perspectives for phylogenetic studies of Aphididae. [ABSTRACT FROM AUTHOR]