Repetitive Sequences, Codon Usage Bias and Phylogenetic Analysis of the Plastome of Miliusa glochidioides.

Annonaceae is the largest family in Magnoliales, exhibiting the greatest diversity among and within genera. In this study, we conducted an analysis of repetitive sequences and codon usage bias in the previously acquired plastome of Miliusa glochidioides. Using a concatenated dataset of shared genes, we constructed the phylogenetic relationships among 27 Annonaceae species. The results showed that the size of the plastomes in the Annonaceae ranged from 159 to 202 kb, with the size of the inverted repeat region ranging from 40 to 65 kb. Within the plastome of M. glochidioides, we identified 42 SSRs, 36 tandem repeats, and 9 dispersed repeats. These SSRs consist of three nucleotide types and eight motif types, with a preference for A/T bases, primarily located in the large single-copy regions and intergenic spacers. Tandem and dispersed repeat sequences were predominantly detected in the IR region. Through codon usage bias analysis, we identified 30 high-frequency codons and 11 optimal codons. The plastome of M. glochidioides demonstrated relatively weak codon usage bias, favoring codons with A/T endings, primarily influenced by natural selection. Phylogenetic analysis revealed that all four subfamilies formed monophyletic groups, with Cananga odorata (Ambavioideae) and Anaxagorea javanica (Anaxagoreoideae) successively nested outside Annonoideae + Malmeoideae. These findings improve our understanding of the plastome of M. glochidioides and provide additional insights for studying plastome evolution in Annonaceae.

The complete chloroplast genome of Miliusa glochidioides (Annonaceae) and phylogenetic analysis.

The chloroplast (cp) genome of Miliusa glochidioides has been fully sequenced. The cp genome of this species has a typical quadripartite structure comprised of four parts: a large single copy (LSC; 88,782 bp) region, a small single copy (SSC; 18,949 bp) region, and two inverted repeat (IR; 26,029 bp each) regions. The full length of the cp genome is 159,789 bp; its GC content is 36.7%, and it encodes a total of 129 genes including 84 protein-coding genes, 37 tRNA genes, and 8 rRNA genes. Among the protein-coding genes, nine (rps16, rpl2, rpl16, atpF, rpoC1, petB, petD, ndhA, and ndhB) contain one intron, and three (rps12, clpP, and ycf3) have two introns. A maximum-likelihood (ML) phylogenetic tree shows that M. glochidioides is a sister to Chieniodendron hainanense.