Analysis of the complete mitochondrial genome of Panax quinquefolius reveals shifts from cis-splicing to trans-splicing of intron cox2i373.

Panax quinquefolius is a perennial plant with medicinal values. In this study, we assembled the complete mitochondrial genome (mitogenome) of P. quinquefolius using PMAT assembler. The total length of P. quinquefolius mitogenome is 573,154 bp. We annotated a total of 34 protein-coding genes (PCGs), 35 tRNA genes, and 6 rRNA genes in this mitogenome. The analysis of repetitive elements shows that there are 153 SSRs, 24 tandem repeats and 242 pairs of dispersed repeats this mitogenome. Also, we found 24 homologous sequences with a total length of 64,070 bp among its mitogenome and plastome, accounting for 41.05 % of the plastome, and 11.18 % of the mitogenome, showing a remarkable frequent sequence dialogue between plastome and mitogenomes. Besides, a total of 583 C to U RNA editing sites on 34 PCGs of high confidence were predicted by using Deepred-mt. We also inferred the phylogenetic relationships of P. quinquefolius and other angiosperms based on mitochondrial PCGs. Finally, we observed a shift from cis- to trans-splicing in P. quinquefolius for two mitochondrial introns, namely cox2i373 and nad1i728, and a pair of 48 bp short repetitive sequences may be associated with the breaking and rearrangement of the cox2i373 intron. The fragmentation of the cox2i373 intron was further confirmed by our PCR amplification experiments. In summary, our report on the P. quinquefolius mitogenome provides a new perspective on the intron evolution of the mitogenome.

Comprehensive analysis of the mitochondrial genome of Rehmannia glutinosa: insights into repeat-mediated recombinations and RNA editing-induced stop codon acquisition.

Rehmannia glutinosa is an economically significant medicinal plant. Yet, the structure and sequence of its mitochondrial genome has not been published, which plays a crucial role in evolutionary analysis and regulating respiratory-related macromolecule synthesis. In this study, the R. glutinosa mitogenome was sequenced employing a combination of Illumina short reads and Nanopore long reads, with subsequent assembly using a hybrid strategy. We found that the predominant configuration of the R. glutinosa mitogenome comprises two circular chromosomes. The primary structure of the mitogenome encompasses two mitochondrial chromosomes corresponding to the two major configurations, Mac1-1 and Mac1-2. The R. glutinosa mitogenome encoded an angiosperm-typical set of 24 core genes, nine variable genes, three rRNA genes, and 15 tRNA genes. A phylogenetic analysis using the 16 shared protein-coding genes (PCG) yielded a tree consistent with the phylogeny of Lamiales species and two outgroup taxa. Mapping RNA-seq data to the coding sequences (CDS) of the PCGs revealed 507 C-to-U RNA editing sites across 31 PCGs of the R. glutinosa mitogenome. Furthermore, one start codon (nad4L) and two stop codons (rpl10 and atp6) were identified as products of RNA editing events in the R. glutinosa mitogenome.

Comparative chloroplast genomes study of five officinal Ardisia Species: Unraveling interspecific diversity and evolutionary insights in Ardisia.

Ardisia S.W. (Primulaceae), naturally distributed in tropical and subtropical regions, has edible and medicinal values and is prevalent in clinical and daily use in China. More genetic information for distinct species delineation is needed to support the development and utilization of the genus Ardisia. We sequenced, annotated, and compared the chloroplast genomes of five Ardisia species: A. brunnescens, A. pusilla, A. squamulosa, A. crenata, and A. brevicaulis in this study. We found a typical quadripartite structure in all five chloroplast genomes, with lengths ranging from 155,045 to 156,943 bp. Except for A. pusilla, which lacked the ycf15 gene, the other four Ardisia species contained 114 unique genes, including 79 protein-coding genes, 30 tRNAs, and four rRNAs. In addition, the rps19 pseudogene gene was present only in A. brunnescens. Five highly variable DNA barcodes were identified for five Ardisia species, including trnT-GGU-psbD, trnT-UGU-trnL-UAA, rps4-trnT-UGU, rpl32-trnL-UAG, and rpoB-trnC-GAA. The RNA editiing sites of protein-coding genes in the five Ardisia plastome were characterized and compared, and 274 (A. crenata)-288 (A. brevicaulis) were found. The results of the phylogenetic analysis were consistent with the morphological classification. Sequence alignment and phylogenetic analysis showed that ycf15 genes were highly divergent in Primulaceae. Reconstructions of ancestral character states indicated that leaf margin morphology is critical for classifying the genus Ardisia, with a rodent-like character being the most primitive. These results provide valuable information on the taxonomy and evolution of Ardisia plants.

The Complete Mitochondrial Genome of Paeonia lactiflora Pall. (Saxifragales: Paeoniaceae): Evidence of Gene Transfer from Chloroplast to Mitochondrial Genome.

Paeonia lactiflora (P. lactiflora), a perennial plant renowned for its medicinal roots, provides a unique case for studying the phylogenetic relationships of species based on organelle genomes, as well as the transference of DNA across organelle genomes. In order to investigate this matter, we sequenced and characterized the mitochondrial genome (mitogenome) of P. lactiflora. Similar to the chloroplast genome (cpgenome), the mitogenome of P. lactiflora extends across 181,688 base pairs (bp). Its unique quadripartite structure results from a pair of extensive inverted repeats, each measuring 25,680 bp in length. The annotated mitogenome includes 27 protein-coding genes, 37 tRNAs, 8 rRNAs, and two pseudogenes (rpl5, rpl16). Phylogenetic analysis was performed to identify phylogenetic trees consistent with Paeonia species phylogeny in the APG Ⅳ system. Moreover, a total of 12 MTPT events were identified and 32 RNA editing sites were detected during mitogenome analysis of P. lactiflora. Our research successfully compiled and annotated the mitogenome of P. lactiflora. The study provides valuable insights regarding the taxonomic classification and molecular evolution within the Paeoniaceae family.

Characterizing the chloroplast genome of Mammillaria elongata DC. 1828 in the Cactaceae family and unveiling its phylogenetic affinities within the genus Mammillaria.

With its nearly 200 species, the Mammillaria genus is the most species-rich within the Cactaceae family, yet surprisingly, few of its chloroplast genomes have been studied. We focused on the species Mammillaria elongata DC. 1828, a petite cactus native to Mexico and favored by horticulturists, yet whose phylogenetic relationships remain uncertain due to a lack of genomic data. We extracted the DNA from a sample obtained in China, sequenced it using the NovaSeq 6000 platform, and assembled the chloroplast genome using GetOrganelle software. Our assembly resulted in a chloroplast genome of 110,981 base pairs with an overall GC content of 36.28%, which included 100 genes (95 unique). Notably, several protein-coding genes were absent. Phylogenetic analysis using 59 shared genes across nine Mammillaria species and one Obregonia species revealed that M. elongata and M. gracilis are closely related, suggesting a recent common ancestor and possible shared evolutionary pressures or ecological niches. This study provides crucial genomic data for M. elongata and hints at intriguing phylogenetic relationships within the Mammillaria genus.

Genetic diversity of Coffea arabica L. mitochondrial genomes caused by repeat- mediated recombination and RNA editing.

Background: Coffea arabica L. is one of the most important crops widely cultivated in 70 countries across Asia, Africa, and Latin America. Mitochondria are essential organelles that play critical roles in cellular respiration, metabolism, and differentiation. C. arabica's nuclear and chloroplast genomes have been reported. However, its mitochondrial genome remained unreported. Here, we intended to sequence and characterize its mitochondrial genome to maximize the potential of its genomes for evolutionary studies, molecular breeding, and molecular marker developments. Results: We sequenced the total DNA of C. arabica using Illumina and Nanopore platforms. We then assembled the mitochondrial genome with a hybrid strategy using Unicycler software. We found that the mitochondrial genome comprised two circular chromosomes with lengths of 867,678 bp and 153,529 bp, encoding 40 protein-coding genes, 26 tRNA genes, and three rRNA genes. We also detected 270 Simple Sequence Repeats and 34 tandem repeats in the mitochondrial genome. We found 515 high-scoring sequence pairs (HSPs) for a self-to-self similarity comparison using BLASTn. Three HSPs were found to mediate recombination by the mapping of long reads. Furthermore, we predicted 472 using deep-mt with the convolutional neural network model. Then we randomly validated 90 RNA editing events by PCR amplification and Sanger sequencing, with the majority being non-synonymous substitutions and only three being synonymous substitutions. These findings provide valuable insights into the genetic characteristics of the C. arabica mitochondrial genome, which can be helpful for future study on coffee breeding and mitochondrial genome evolution. Conclusion: Our study sheds new light on the evolution of C. arabica organelle genomes and their potential use in genetic breeding, providing valuable data for developing molecular markers that can improve crop productivity and quality. Furthermore, the discovery of RNA editing events in the mitochondrial genome of C. arabica offers insights into the regulation of gene expression in this species, contributing to a better understanding of coffee genetics and evolution.

Comparative analysis of the plastid and mitochondrial genomes of Artemisia giraldii Pamp.

Artemisia giraldii Pamp. is an herbaceous plant distributed only in some areas in China. To understand the evolutionary relationship between plastid and mitochondria in A. giraldii, we sequenced and analysed the plastome and mitogenome of A. giraldii on the basis of Illumina and Nanopore DNA sequencing data. The mitogenome was 194,298 bp long, and the plastome was 151,072 bp long. The mitogenome encoded 56 genes, and the overall GC content was 45.66%. Phylogenetic analysis of the two organelle genomes revealed that A. giraldii is located in the same branching position. We found 13 pairs of homologous sequences between the plastome and mitogenome, and only one of them might have transferred from the plastid to the mitochondria. Gene selection pressure analysis in the mitogenome showed that ccmFc, nad1, nad6, atp9, atp1 and rps12 may undergo positive selection. According to the 18 available plastome sequences, we found 17 variant sites in two hypervariable regions that can be used in completely distinguishing 18 Artemisia species. The most interesting discovery was that the mitogenome of A. giraldii was only 43,226 bp larger than the plastome. To the best of our knowledge, this study represented one of the smallest differences between all sequenced mitogenomes and plastomes from vascular plants. The above results can provide a reference for future taxonomic and molecular evolution studies of Asteraceae species.