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.

RNA editing is a crucial mechanism regulating gene expression in plant organellar genomes, which optimizes protein structures through base substitution and plays a vital role in plant growth, development, and stress adaptation. This study revises the conventional understanding restricting MORF proteins to seed plants by reporting their first identification in ferns, an early vascular plant lineage. We sequenced chloroplast genomes of O. japonica and P. vachellii, revealing one MORF9 homolog in O. japonica and three homologs (MORF1/8/9) in P. vachellii through comparative transcriptomics and structural validation. All identified MORF proteins harbor conserved MORF-box domains, suggesting structural and potentially functional conservation with angiosperms. Crucially, MORF members differentially regulate organellar RNA editing: chloroplast editing frequencies are predicted to show dose-dependent enhancement (0.7–1.0 in conserved sites), potentially influenced by MORF presence or copy number. In O. japonica, chloroplast editing exhibits tissue-specific patterns (conserved sites 0.7–1.0; tissue-specific sites lower efficiency at 0.1–0.2), while this study’s mitochondrial editing results show a balanced frequency distribution (0–1 range). Amino acid substitution analysis demonstrates MORF-mediated hydrophobic optimization (Ser→Leu > 30%, Pro→Leu > 18%), likely underpinning fern adaptability. This work provides crucial initial evidence for a conserved MORF-mediated RNA editing module shared between these early vascular plants (ferns) and angiosperms, offering fundamental insights into the evolutionary trajectory of plant organellar gene regulation.

In recent years, the evolution and phylogeny of plastid genomes have attracted much attention from scholars all over the world. Annonaceae is the largest family in Magnoliales with the greatest diversity among and within genera. Thus comparative analyses of its plastomes will be informative. In this study, the complete chloroplast genome ofMiliusa glochidioideswas sequenced by next-generation sequencing technology. Using two Magnoliaceae species as out-group, a comparative analysis of the existing 13 Annonaceae plastomes was conducted, and a phylogenetic relationship was constructed based on four methods. Our results show that the Annonaceae plastomes have great variation in the evolution process. The genome size is between 159kb and 202kb while the gene content ranges from 127 to 165. The number of genes in the IR region is between 5 and 39. Plastomes underwent significant structural rearrangements, including one inversion and multiple large-scale expansion (6-20kb) in the lR region, and shrinkage and inversions in the SSC region. Compared with Magnoliaceae, two fragments (pafII-atpEand 5'-rps12-psbJ) were inversed in Annonaceae. The phylogenetic relationship based on 78 common protein genes showed thatCananga odoratawas located at the base of Annonaceae. Annonoideae was a monophyletic group, andChieniodendron hainanensewas located inside the Malmeoideae. A total of 737 simple sequence repeats (SSRs) were detected in the study, and the distribution of SSRs varied from species. It is mainly dominated by A/T bases (mononucleotide) and is located in the intergenic region. In conclusion, the plastomes of Annonaceae have undergone great variation during evolution, especially the large-scale expansion of the IR region. Our study provides more information for studying the plastome evolution of Annonaceae.