Organelle Genomes Research Articles

PMAT: an efficient plant mitogenome assembly toolkit using low-coverage HiFi sequencing data.

Complete mitochondrial genomes (mitogenomes) of plants are valuable resources for nucleocytoplasmic interactions, plant evolution, and plant cytoplasmic male sterile line breeding. However, the complete assembly of plant mitogenomes is challenging due to frequent recombination events and horizontal gene transfers. Previous studies have adopted Illumina, PacBio, and Nanopore sequencing data to assemble plant mitogenomes, but the poor assembly completeness, low sequencing accuracy, and high cost limit the sampling capacity. Here, we present an efficient assembly toolkit (PMAT) for de novo assembly of plant mitogenomes using low-coverage HiFi sequencing data. PMAT has been applied to the de novo assembly of 13 broadly representative plant mitogenomes, outperforming existing organelle genome assemblers in terms of assembly accuracy and completeness. By evaluating the assembly of plant mitogenomes from different sequencing data, it was confirmed that PMAT only requires 1× HiFi sequencing data to obtain a complete plant mitogenome. The source code for PMAT is available at https://github.com/bichangwei/PMAT. The developed PMAT toolkit will indeed accelerate the understanding of evolutionary variation and breeding application of plant mitogenomes.

Decoding the complete organelle genomic architecture of Stewartia gemmata: an early-diverging species in Theaceae

BackgroundTheaceae, comprising 300 + species, holds significance in biodiversity, economics, and culture, notably including the globally consumed tea plant. Stewartia gemmata, a species of the earliest diverging tribe Stewartieae, is critical to offer insights into Theaceae's origin and evolutionary history.ResultWe sequenced the complete organelle genomes of Stewartia gemmata using short/long reads sequencing technologies. The chloroplast genome (158,406 bp) exhibited a quadripartite structure including the large single-copy region (LSC), a small single-copy region (SSC), and a pair of inverted repeat regions (IRs); 114 genes encoded 80 proteins, 30 tRNAs, and four rRNAs. The mitochondrial genome (681,203 bp) exhibited alternative conformations alongside a monocyclic structure: 61 genes encoding 38 proteins, 20 tRNAs, three rRNAs, and RNA editing-impacting genes, including ATP6, RPL16, COX2, NAD4L, NAD5, NAD7, and RPS1. Comparative analyses revealed frequent recombination events and apparent rRNA gene gains and losses in the mitochondrial genome of Theaceae. In organelle genomes, the protein-coding genes exhibited a strong A/U bias at codon endings; ENC-GC3 analysis implies selection-driven codon bias. Transposable elements might facilitate interorganelle sequence transfer. Phylogenetic analysis confirmed Stewartieae's early divergence within Theaceae, shedding light on organelle genome characteristics and evolution in Theaceae.ConclusionsWe studied the detailed characterization of organelle genomes, including genome structure, composition, and repeated sequences, along with the identification of lateral gene transfer (LGT) events and complexities. The discovery of a large number of repetitive sequences and simple sequence repeats (SSRs) has led to new insights into molecular phylogenetic markers. Decoding the Stewartia gemmata organellar genome provides valuable genomic resources for further studies in tea plant phylogenomics and evolutionary biology.

Comprehensive Analysis of the Complete Mitochondrial Genome of Rehmannia chingii: An Autotrophic Species in the Orobanchaceae Family.

Rehmannia chingii is an important medicinal plant with immense value in scientific research. However, its mitochondrial genome (mitogenome) has not yet been characterized. Herein, based on whole-genome Illumina short reads and PacBio HiFi reads, we obtained the complete mitogenome of R. chingii through a de novo assembly strategy. We carried out comparative genomic analyses and found that, in comparison with the plastid genome (plastome) showing a high degree of structural conservation, the R. chingii mitogenome structure is relatively complex, showing an intricate ring structure with 16 connections, owing to five repetitive sequences. The R. chingii mitogenome was 783,161 bp with a GC content of 44.8% and contained 77 genes, comprising 47 protein-coding genes (CDS), 27 tRNA genes, and 3 rRNA genes. We counted 579 RNA editing events in 47 CDS and 12,828 codons in all CDSs of the R. chingii mitogenome. Furthermore, 24 unique sequence transfer fragments were found between the mitogenome and plastome, comprising 8 mitogenome CDS genes and 16 plastome CDS genes, corresponding to 2.39% of the R. chingii mitogenome. Mitogenomes had shorter but more collinear regions, evidenced by a comparison of the organelles of non-parasitic R. chingii, hemiparasitic Pedicularis chinensis, and holoparasitic Aeginetia indica in the Orobanchaceae family. Moreover, from non-parasitic to holoparasitic species, the genome size in the mitogenomes of Orobanchaceae species did not decrease gradually. Instead, the smallest mitogenome was found in the hemiparasitic species P. chinensis, with a size of 225,612 bp. The findings fill the gap in the mitogenome research of the medicinal plant R. chingii, promote the progress of the organelle genome research of the Orobanchaceae family, and provide clues for molecular breeding.

Remarkable mitochondrial genome heterogeneity in Meniocus linifolius (Brassicaceae).

Detailed analyses of 16 genomes identified a remarkable acceleration of mutation rate, hence mitochondrial sequence and structural heterogeneity, in Meniocus linifolius (Brassicaceae). The powerhouse, mitochondria, in plantsfeature high levels of structural variation, while the encoded genes are normally conserved. However, the substitution rates and spectra of mitochondria DNA within the Brassicaceae, a family with substantial scientific and economic importance, have not been adequately deciphered. Here, by analyzing three newly assembled and 13 known mitochondrial genomes (mitogenomes), we report the highly variable genome structure and mutation rates in Brassicaceae. The genome sizes and GC contents are 196,604bp and 46.83%, 288,122bp and 44.79%, and 287,054bp and 44.93%, for Meniocus linifolius (Mli), Crucihimalaya lasiocarpa (Cla), and Lepidium sativum (Lsa), respectively. In total, 29, 33, and 34 protein-coding genes (PCGs) and 14, 18, and 18 tRNAs are annotated for Mli, Cla, and Lsa, respectively, while all mitogenomes contain one complete circular molecule with three rRNAs and abundant RNA editingsites.The Mli mitogenome features four conformations likely mediatedby the two pairs of long repeats, while at the same time seems to have an unusual evolutionary history due to higher GC content, loss of more genes and sequences, but having more repeats and plastid DNA insertions. Corroborating with these, an ambiguous phylogenetic position with long branch length and elevated synonymous substitution rate in nearly all PCGs are observed for Mli. Taken together, our results reveal a high level of mitogenome heterogeneity at the family level and provide valuable resources for further understanding the evolutionary pattern of organelle genomes in Brassicaceae.

An eFP reference gene expression atlas for mangosteen

Mangosteen is the queen of fruits with many health benefits and high pharmaceutical potential but remains an underutilized crop. There are several reports of mangosteen organelle genomes and transcriptomes from various tissues but a reference genome or transcriptome is still lacking. In this study, we aimed to generate a publicly accessible reference transcriptome of Garcinia mangostana variety Manggis (local fruit in Southeast Asia) to facilitate research in mangosteen functional genomics. De novo assembly was performed using Trinity with all the Illumina sequence datasets and generated 369,861 transcripts with an N50 of 1,433 bp. SuperTranscripts and TGICL transcript clustering approaches were taken to reduce redundant transcripts, in which the latter generated a more comprehensive reference transcriptome with a higher N50 value, Benchmarking Universal Single-Copy Orthologs (BUSCO) score, and read mapping rates. A total of 118,165 (43.7 %) unigenes were functionally annotated. To visualize gene expression across different mangosteen tissues, developmental stages, and experiments based on the reference transcriptome, we constructed a mangosteen electronic Fluorescent Pictograph (eFP) browser. This allows users to easily visualize the expression of genes in absolute, relative, and compare modes. In addition, researchers can perform online BLAST search against the in-house BAR SequenceServer for homologous sequences that match mangosteen transcripts to explore corresponding expression patterns via direct links to the eFP browser. This reference transcriptome and eFP browser (accessible at https://bar.utoronto.ca/efp_mangosteen/cgi-bin/efpWeb.cgi) provide a useful online tool for future research and improvement of mangosteen.

Comparative analysis of organelle genomes provides conflicting evidence between morphological similarity and phylogenetic relationship in diatoms

Diatoms (Bacillariophyta) are abundant phytoplankton groups in marine environments, which contribute approximately 20% of global carbon fixation through photosynthesis. Moreover, diatoms exhibit the highest species diversity (approximately 18,000 diatom species) among marine photosynthetic eukaryotes, which were identified by morphological characteristics. Molecular phylogenetic analyses could shed new insights into the evolutionary relationships of diverse diatom species. Nevertheless, a comprehensive understanding of the phylogenetic relationships of diatom species still remains unclear because the available molecular data are insufficient compared with their high species diversity. Furthermore, several novel diatom species were reported from field samples with no molecular evidence. In particular, the phylogenies of diatom species constructed using organelle genomes revealed that several diatom genera are paraphyletic with high supporting values. We constructed high-resolution phylogenetic trees of diatom species using organelle genomes (plastids and mitochondria) and compared the morphologies in several paraphyletic diatom genera. Especially, the clades Nitzschia and Thalassiosira include several different diatom genera with high phylogenetic supports. Our study demonstrated that some morphological characteristics (e.g., genus characters) of several diatom genera could not represent current genus boundaries. Based on the results, we highlight the necessity for taxonomic reinvestigation. To reestablish this in diatoms, it will be essential to incorporate more genome data from a broader range of taxon samples, along with a comparison of morphological characteristics.

Asteraceae genome database: a comprehensive platform for Asteraceae genomics.

Asteraceae, the largest family of angiosperms, has attracted widespread attention for its exceptional medicinal, horticultural, and ornamental value. However, researches on Asteraceae plants face challenges due to their intricate genetic background. With the continuous advancement of sequencing technology, a vast number of genomes and genetic resources from Asteraceae species have been accumulated. This has spurred a demand for comprehensive genomic analysis within this diverse plant group. To meet this need, we developed the Asteraceae Genomics Database (AGD; http://cbcb.cdutcm.edu.cn/AGD/). The AGD serves as a centralized and systematic resource, empowering researchers in various fields such as gene annotation, gene family analysis, evolutionary biology, and genetic breeding. AGD not only encompasses high-quality genomic sequences, and organelle genome data, but also provides a wide range of analytical tools, including BLAST, JBrowse, SSR Finder, HmmSearch, Heatmap, Primer3, PlantiSMASH, and CRISPRCasFinder. These tools enable users to conveniently query, analyze, and compare genomic information across various Asteraceae species. The establishment of AGD holds great significance in advancing Asteraceae genomics, promoting genetic breeding, and safeguarding biodiversity by providing researchers with a comprehensive and user-friendly genomics resource platform.

AlliumDB: a central portal for comparative and functional genomics in Allium.

The genus Allium belongs to the botanical family Amaryllidaceae and includes economically important crops such as onion, garlic, bunching onion, and leek, used as vegetables, spices, and traditional medicines. The large sizes of Allium genomes hamper the genetic dissection of agronomically important traits and molecular breeding. With the growing accumulation of genomic, resequencing, transcriptome, and phenotypic data, the demand for an integrative Allium database is increasing. Here we present a user-friendly database, AlliumDB (https://allium.qau.edu.cn), as a functional genomics hub integrating public and in-house data. The database contains all currently available nuclear and organelle genomes for Allium species, with genes comprehensively annotated based on Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses, orthology, gene families, protein families (Pfam), and non-coding RNA families (Rfam). Transcriptome and variation profiles are integrated into dynamic visualization tools. We took phenotypic photographs and generated trait records for hundreds of Allium germplasms collected worldwide, which are included in the database. We incorporated JBrowse for the visualization of gene structures, RNA sequencing data, and variation data. Analysis tools such as the basic local alignment search tool (BLAST), sequence fetch, enrichment, and motif analyses are available to explore potential gene functions. This database incorporates comprehensive Allium genotypic and phenotypic datasets. As the community assembles new genomes and generates resequencing data for Allium germplasms, the database will be improved and continuously updated with these multi-omics data and comparative genomic studies. We expect the AlliumDB database to become a key resource for the study of Allium crops.

Paternal leakage of plastids rescues inter-lineage hybrids in Silene nutans.

Organelle genomes are usually maternally inherited in angiosperms. However, biparental inheritance has been observed, especially in hybrids resulting from crosses between divergent genetic lineages. When it concerns the plastid genome, this exceptional mode of inheritance might rescue inter-lineage hybrids suffering from plastid-nuclear incompatibilities. Genetically differentiated lineages of Silene nutans exhibit strong postzygotic isolation owing to plastid-nuclear incompatibilities, highlighted by inter-lineage hybrid chlorosis and mortality. Surviving hybrids can exhibit variegated leaves, which might indicate paternal leakage of the plastid genome. We tested whether the surviving hybrids inherited the paternal plastid genome and survived thanks to paternal leakage. We characterized the leaf phenotype (fully green, variegated or white) of 504 surviving inter-lineage hybrids obtained from a reciprocal cross experiment among populations of four genetic lineages (W1, W2, W3 and E1) of S. nutans from Western Europe and genotyped 560 leaf samples (both green and white leaves for variegated hybrids) using six lineage-specific plastid single nucleotide polymorphisms. A high proportion of the surviving hybrids (≤98 %) inherited the paternal plastid genome, indicating paternal leakage. The level of paternal leakage depended on cross type and cross direction. The E1 and W2 lineages as maternal lineages led to the highest hybrid mortality and to the highest paternal leakage from W1 and W3 lineages in the few surviving hybrids. This was consistent with E1 and W2 lineages, which contained the most divergent plastid genomes. When W3 was the mother, more hybrids survived, and no paternal leakage was detected. By providing a plastid genome potentially more compatible with the hybrid nuclear background, paternal leakage has the potential to rescue inter-lineage hybrids from plastid-nuclear incompatibilities. This phenomenon might slow down the speciation process, provided hybrid survival and reproduction can occur in the wild.

Whole mitochondrial and chloroplast genome sequencing of Tunisian date palm cultivars: diversity and evolutionary relationships

BackgroundDate palm (Phoenix dactylifera L.) is the most widespread crop in arid and semi-arid regions and has great traditional and socioeconomic importance, with its fruit well-known for its high nutritional and health value. However, the genetic variation of date palm cultivars is often neglected. The advent of high-throughput sequencing has made possible the resequencing of whole organelle (mitochondria and chloroplast) genomes to explore the genetic diversity and phylogenetic relationships of cultivated plants with unprecedented detail.ResultsWhole organelle genomes of 171 Tunisian accessions (135 females and 36 males) were sequenced. Targeted bioinformatics pipelines were used to identify date palm haplotypes and genome variants, aiming to provide variant annotation and investigate patterns of evolutionary relationship. Our results revealed the existence of unique haplotypes, identified by 45 chloroplastic and 156 mitochondrial SNPs. Estimation of the effect of these SNPs on genes functions was predicted in silico.ConclusionsThe results of this study have important implications, in the light of ongoing environmental changes, for the conservation and sustainable use of the genetic resources of date palm cultivars in Tunisia, where monoculture threatens biodiversity leading to genetic erosion. These data will be useful for breeding and genetic improvement programs of the date palm through selective cross-breeding.

Intrageneric structural variation in organelle genomes from the genus Dystaenia (Apiaceae): genome rearrangement and mitochondrion-to-plastid DNA transfer.

During plant evolution, intracellular DNA transfer (IDT) occurs not only from organelles to the nucleus but also between organelles. To further comprehend these events, both organelle genomes and transcriptomes are needed. In this study, we constructed organelle genomes and transcriptomes for two Dystaenia species and described their dynamic IDTs between their nuclear and mitochondrial genomes, or plastid and mitochondrial genomes (plastome and mitogenome). We identified the putative functional transfers of the mitochondrial genes 5' rpl2, rps10, rps14, rps19, and sdh3 to the nucleus in both Dystaenia species and detected two transcripts for the rpl2 and sdh3 genes. Additional transcriptomes from the Apicaceae species also provided evidence for the transfers and duplications of these mitochondrial genes, showing lineage-specific patterns. Intrageneric variations of the IDT were found between the Dystaenia organelle genomes. Recurrent plastid-to-mitochondrion DNA transfer events were only identified in the D. takeshimana mitogenome, and a pair of mitochondrial DNAs of plastid origin (MIPTs) may generate minor alternative isoforms. We only found a mitochondrion-to-plastid DNA transfer event in the D. ibukiensis plastome. This event may be linked to inverted repeat boundary shifts in its plastome. We inferred that the insertion region involved an MIPT that had already acquired a plastid sequence in its mitogenome via IDT. We propose that the MIPT acts as a homologous region pairing between the donor and recipient sequences. Our results provide insight into the evolution of organelle genomes across the family Apiaceae.

Characterization and comparative analysis of the complete organelle genomes of three red macroalgae species (Neoporphyra dentata, Neoporphyra seriata, and Neopyropia yezoensis) and development of molecular makers for their identification.

Many species of red algae belonging to the phylum Rhodophyta are consumed by humans as raw materials for nutrition and medicine. As the seaweed market grows, the importance of the laver species has increased. The classification of red algal species has changed significantly, and the accuracy of this classification has improved significantly in recent years. Here, we report the complete circular genomes of the chloroplasts (cp) and mitochondria (mt) of three laver species (Neoporphyra dentata, Neoporphyra seriata, and Neopyropia yezoensis). This study aims to assemble, annotate, and characterize the organization of the organelle genomes of three laver species, conduct comparative genomic studies, and develop molecular markers based on SNPs. We analyzed organelle genome structures, repeat sequences, sequence divergence, gene rearrangements, and phylogenetic relationships of three laver species. The chloroplast genomes of the three species contained an average of 212 protein-coding genes (PCGs), while the mitochondrial genomes contained an average of 25 PCGs. We reconstructed the phylogenetic trees based on both chloroplast and mitochondrial genomes using 201 and 23 PCGs (in cp and mt genomes, respectively) shared in the class Bangiophyceae (and five species of Florideophyceae class used as an outgroup). In addition, 12 species-specific molecular markers were developed for qRT-PCR analysis. This is the first report of Neoporphyra seriata complete organellar genomes. With the results, this study provides useful genetic information regarding taxonomic discrepancies, the reconstruction of phylogenetic trees, and the evolution of red algae. Moreover, the species-specific markers can be used as fast and easy methods to identify a target species.

An improved reference genome and first organelle genomes of Quercus suber

Cork oak (Quercus suber L.) is an ecologically and economically important evergreen tree species native to the Mediterranean region and widespread in southwest Europe and northwest Africa. An improved genome assembly of cork oak using a combination of Illumina and PacBio sequencing is presented in this study. The assembled genome contains 2351 scaffolds longer than 1000 bp, accounting for 765.7 Mbp of genome size, L90 of 755, and a N50 of 1.0 Mbp, with 40,131 annotated genes. The repetitive sequences constitute 53.6% of the genome. The genome sequences of chloroplast and mitochondrion were determined for the first time, with a genome size of 161,179 bp and 531,858 bp, respectively. Phylogenetic analysis based on complete chloroplast genome sequence showed that Q. suber is closely related to Quercus variabilis, two cork-producing species with commercial use. All data generated are available through the public databases, being ready to be used without restrictions. This study provides an improved nuclear genome assembly together with the organelle genomes of cork oak. These resources will be useful for further breeding strategies and conservation programs and for comparative genomic studies in oak species.

The genome sequence of the chlorophyte Dunaliella primolecta CCAP 11/34 (Butcher, 1959)

We present a genome assembly from a colony of Dunaliella primolecta (Chlorophyta; Chlorophyceae; Chlamydomonadales; Dunaliellaceae). The genome sequence is 211 megabases in span. Most of the assembly (91.36%) is scaffolded into 16 chromosomal pseudomolecules. The organelle genomes have also been assembled, and the mitochondrial genome was 41.6 kilobases in length and the plastid genome is 242.6 kilobases long.

Stochastic organelle genome segregation through Arabidopsis development and reproduction.

Organelle DNA (oDNA) in mitochondria and plastids is vital for plant (and eukaryotic) life. Selection against damaged oDNA is mediated in part by segregation - sorting different oDNA types into different cells in the germline. Plants segregate oDNA very rapidly, with oDNA recombination protein MSH1 a key driver of this segregation, but we have limited knowledge of the dynamics of this segregation within plants and between generations. Here, we reveal how oDNA evolves through Arabidopsis thaliana development and reproduction. We combine stochastic modelling, Bayesian inference, and model selection with new and existing tissue-specific oDNA measurements from heteroplasmic Arabidopsis plant lines through development and between generations. Segregation proceeds gradually but continually during plant development, with a more rapid increase between inflorescence formation and the next generation. When MSH1 is compromised, the majority of observed segregation can be achieved through partitioning at cell divisions. When MSH1 is functional, mtDNA segregation is far more rapid; we show that increased oDNA gene conversion is a plausible mechanism quantitatively explaining this acceleration. These findings reveal the quantitative, time-dependent details of oDNA segregation in Arabidopsis. We also discuss the support for different models of the plant germline provided by these observations.

Development of a SNaPshot assay for the genotyping of organellar SNPs in four closely related pines

Mitochondrial (mtDNA) and chloroplast (cpDNA) polymorphisms are valuable resources to study past demographic changes, phylogenetics and evolution, especially in forest tree species, where these genomes are haploid and uniparentally transferred. The organellar markers were usually scored separately using direct sequencing or PCR-based approaches, which can be time-consuming and expensive, especially in large-scale population genetics research. In this study, we developed an efficient and cost-effective SNaPshot assay for genotyping preselected ­mtDNA and cpDNA polymorphism in four closely related pine species including Scots pine (Pinus sylvestris L.) and three taxa from the Pinus mugo complex. We validated the method by genotyping the samples derived from 12 populations of the species from their wide geographical distribution range in Europe. The results proved high accuracy of the method with a genotyping success rate of 99.7%. The set of assayed markers shows significant genetic variation. By using multiplex SNaPshot assay, we provided an efficient and sensitive molecular tool for intra- and interspecific genetic analyses. The presented protocol is useful for fast and relatively cheap SNP genotyping of organelle genome of closely related pine species. The assayed SNPs allow studying the species discrimination and detailed investigations of their population history and structure. Given its numerous benefits and efficient genotyping rate, the SNaPshot method appears to be a valuable and practical resource for studying the genetic makeup of forest tree species. Particularly, it proves to be advantageous for population genetics.

Assembly and annotation of the black spruce genome provide insights on spruce phylogeny and evolution of stress response.

Black spruce (Picea mariana [Mill.] B.S.P.) is a dominant conifer species in the North American boreal forest that plays important ecological and economic roles. Here, we present the first genome assembly of P. mariana with a reconstructed genome size of 18.3 Gbp and NG50 scaffold length of 36.0 kbp. A total of 66,332 protein-coding sequences were predicted in silico and annotated based on sequence homology. We analyzed the evolutionary relationships between P. mariana and 5 other spruces for which complete nuclear and organelle genome sequences were available. The phylogenetic tree estimated from mitochondrial genome sequences agrees with biogeography; specifically, P. mariana was strongly supported as a sister lineage to P. glauca and 3 other taxa found in western North America, followed by the European Picea abies. We obtained mixed topologies with weaker statistical support in phylogenetic trees estimated from nuclear and chloroplast genome sequences, indicative of ancient reticulate evolution affecting these 2 genomes. Clustering of protein-coding sequences from the 6 Picea taxa and 2 Pinus species resulted in 34,776 orthogroups, 560 of which appeared to be specific to P. mariana. Analysis of these specific orthogroups and dN/dS analysis of positive selection signatures for 497 single-copy orthogroups identified gene functions mostly related to plant development and stress response. The P. mariana genome assembly and annotation provides a valuable resource for forest genetics research and applications in this broadly distributed species, especially in relation to climate adaptation.

Multiple configurations of the plastid and mitochondrial genomes of Caragana spinosa.

In this study, we assembled the complete plastome and mitogenome of Caragana spinosa and explored the multiple configurations of the organelle genomes. Caragana spinosa belongs to the Papilionoidea subfamily and has significant pharmaceutical value. To explore the possible interaction between the organelle genomes, we assembled and analyzed the plastome and mitogenome of C. spinosa using the Illumina and Nanopore DNA sequencing data. The plastome of C. spinosa was 129,995bp belonging to the inverted repeat lacking clade (IRLC), which contained 77 protein-coding genes, 29 tRNA genes, and four rRNA genes. The mitogenome was 378,373bp long and encoded 54 unique genes, including 33 protein-coding, three ribosomal RNA (rRNA), and 18 transfer RNA (tRNA) genes. In addition to the single circular conformation, alternative conformations mediated by one and four repetitive sequences in the plastome and mitogenome were identified and validated, respectively. The inverted repeat (PDR12, the 12th dispersed repeat sequence in C. spinosa plastome) of plastome mediating recombinant was conserved in the genus Caragana. Furthermore, we identified 14 homologous fragments by comparing the sequences of mitogenome and plastome, including eight complete tRNA genes. A phylogenetic analysis of protein-coding genes extracted from the plastid and mitochondrial genomes revealed congruent topologies. Analyses of sequence divergence found one intergenic region, trnN-GUU-ycf1, exhibiting a high degree of variation, which can be used to develop novel molecular markers to distinguish the nine Caragana species accurately. This plastome and mitogenome of C. spinosa could provide critical information for the molecular breeding of C. spinosa and be used as a reference genome for other species of Caragana. In this study, we assembled the complete plastome and mitogenome of Caragana spinosa and explored the multiple configurations of the organelle genomes.

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

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. 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. 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.

Characterization and organelle genome sequencing of Pyropia species from Myanmar

Pyropia is a genus comprising red algae of the Bangiaceae family that is commonly found in intertidal zones worldwide. However, understanding of Pyropia species that are prone to tropical regions remains limited despite recent breakthroughs in genomic research. Within the realm of Pyropia species thriving in tropical regions, P. vietnamensis stands out as a widely recognized species. In this study, we aimed to investigate Pyropia species in the southwest coast of Myanmar using physiological and molecular approaches, culture-based analyses, chloroplast rbcL and nuclear SSU gene sequencing, and whole chloroplast and mitochondrial genome sequencing. Physiological analysis showed that the Myanmar samples were more heat-tolerant than their Japanese counterparts, including those of subtropical origin. Additionally, molecular characterization revealed that the Myanmar samples were closely related to P. vietnamensis from India. This study is the first to sequence the chloroplast and mitochondrial genomes of Pyropia species from tropical regions. A unique deletion event was observed within a ribosomal RNA gene cluster in the chloroplast genome of the studied Pyropia species, which is a deviation from the usual characteristics of most Pyropia species. This study improves current understanding of the physiological and molecular characteristics of this comparatively understudied Pyropia species that grows in tropical regions.