Explore the vast range of titles available.

Summary Free‐living cyanobacteria were entrapped by eukaryotic cells ~2 billion years ago, ultimately giving rise to chloroplasts. After a century of debate, the presence of chloroplast DNA was demonstrated in the 1960s. The first chloroplast genomes were sequenced in the 1980s, followed by ~100 vegetable, fruit, cereal, beverage, oil and starch/sugar crop chloroplast genomes in the past three decades. Foreign genes were expressed in isolated chloroplasts or intact plant cells in the late 1980s and stably integrated into chloroplast genomes, with typically maternal inheritance shown in the 1990s. Since then, chloroplast genomes conferred the highest reported levels of tolerance or resistance to biotic or abiotic stress. Although launching products with agronomic traits in important crops using this concept has been elusive, commercial products developed include enzymes used in everyday life from processing fruit juice, to enhancing water absorption of cotton fibre or removal of stains as laundry detergents and in dye removal in the textile industry. Plastid genome sequences have revealed the framework of green plant phylogeny as well as the intricate history of plastid genome transfer events to other eukaryotes. Discordant historical signals among plastid genes suggest possible variable constraints across the plastome and further understanding and mitigation of these constraints may yield new opportunities for bioengineering. In this review, we trace the evolutionary history of chloroplasts, status of autonomy and recent advances in products developed for everyday use or those advanced to the clinic, including treatment of COVID‐19 patients and SARS‐CoV‐2 vaccine.

Chloroplasts play a crucial role in sustaining life on earth. The availability of over 800 sequenced chloroplast genomes from a variety of land plants has enhanced our understanding of chloroplast biology, intracellular gene transfer, conservation, diversity, and the genetic basis by which chloroplast transgenes can be engineered to enhance plant agronomic traits or to produce high-value agricultural or biomedical products. In this review, we discuss the impact of chloroplast genome sequences on understanding the origins of economically important cultivated species and changes that have taken place during domestication. We also discuss the potential biotechnological applications of chloroplast genomes.

Citrus genus includes some of the most important cultivated fruit trees worldwide. Despite being extensively studied because of its commercial relevance, the origin of cultivated citrus species and the history of its domestication still remain an open question. Here, we present a phylogenetic analysis of the chloroplast genomes of 34 citrus genotypes which constitutes the most comprehensive and detailed study to date on the evolution and variability of the genus Citrus. A statistical model was used to estimate divergence times between the major citrus groups. Additionally, a complete map of the variability across the genome of different citrus species was produced, including single nucleotide variants, heteroplasmic positions, indels (insertions and deletions), and large structural variants. The distribution of all these variants provided further independent support to the phylogeny obtained. An unexpected finding was the high level of heteroplasmy found in several of the analyzed genomes. The use of the complete chloroplast DNA not only paves the way for a better understanding of the phylogenetic relationships within the Citrus genus but also provides original insights into other elusive evolutionary processes, such as chloroplast inheritance, heteroplasmy, and gene selection.

High-throughput sequencing is helping biologists to overcome the difficulties of inferring the phylogenies of recently diverged taxa. The present study analyzes the phylogenetic signal of genomic regions with different inheritance patterns using genome skimming and ddRAD-seq in a species-rich Andean genus (Diplostephium) and its allies. We analyzed the complete nuclear ribosomal cistron, the complete chloroplast genome, a partial mitochondrial genome, and a nuclear-ddRAD matrix separately with phylogenetic methods. We applied several approaches to understand the causes of incongruence among datasets, including simulations and the detection of introgression using the D-statistic (ABBA-BABA test). We found significant incongruence among the nuclear, chloroplast, and mitochondrial phylogenies. The strong signal of hybridization found by simulations and the D-statistic among genera and inside the main clades of Diplostephium indicate reticulate evolution as a main cause of phylogenetic incongruence. Our results add evidence for a major role of reticulate evolution in events of rapid diversification. Hybridization and introgression confound chloroplast and mitochondrial phylogenies in relation to the species tree as a result of the uniparental inheritance of these genomic regions. Practical implications regarding the prevalence of hybridization are discussed in relation to the phylogenetic method.

Background The endosymbiosis of the bacterial progenitors of the mitochondrion and the chloroplast are landmark events in the evolution of life on Earth. While both organelles have retained substantial proteomic and biochemical complexity, this complexity is not reflected in the content of their genomes. Instead, the organellar genomes encode fewer than 5% of the genes found in living relatives of their ancestors. While many of the 95% of missing organellar genes have been discarded, others have been transferred to the host nuclear genome through a process known as endosymbiotic gene transfer. Results Here, we demonstrate that the difference in the per-cell copy number of the organellar and nuclear genomes presents an energetic incentive to the cell to either delete organellar genes or transfer them to the nuclear genome. We show that, for the majority of transferred organellar genes, the energy saved by nuclear transfer exceeds the costs incurred from importing the encoded protein into the organelle where it can provide its function. Finally, we show that the net energy saved by endosymbiotic gene transfer can constitute an appreciable proportion of total cellular energy budgets and is therefore sufficient to impart a selectable advantage to the cell. Conclusion Thus, reduced cellular cost and improved energy efficiency likely played a role in the reductive evolution of mitochondrial and chloroplast genomes and the transfer of organellar genes to the nuclear genome.

Background The genus Zingiber of the Zingiberaceae is distributed in tropical, subtropical, and in Far East Asia. This genus contains about 100–150 species, with many species valued as important agricultural, medicinal and horticultural resources. However, genomic resources and suitable molecular markers for species identification are currently sparse. Results We conducted comparative genomics and phylogenetic analyses on Zingiber species. The Zingiber chloroplast genome (size range 162,507–163,711 bp) possess typical quadripartite structures that consist of a large single copy (LSC, 86,986–88,200 bp), a small single copy (SSC, 15,498–15,891 bp) and a pair of inverted repeats (IRs, 29,765–29,934 bp). The genomes contain 113 unique genes, including 79 protein coding genes, 30 tRNA and 4 rRNA genes. The genome structures, gene contents, amino acid frequencies, codon usage patterns, RNA editing sites, simple sequence repeats and long repeats are conservative in the genomes of Zingiber . The analysis of sequence divergence indicates that the following genes undergo positive selection ( ccsA, ndhA, ndhB, petD, psbA, psbB, psbC, rbcL, rpl12, rpl20, rpl23, rpl33, rpoC2, rps7, rps12 and ycf3 ). Eight highly variable regions are identified including seven intergenic regions ( petA-pabJ , rbcL-accD , rpl32-trnL-UAG , rps16-trnQ-UUG , trnC-GCA-psbM , psbC-trnS-UGA and ndhF-rpl32 ) and one genic regions ( ycf1 ). The phylogenetic analysis revealed that the sect. Zingiber was sister to sect. Cryptanthium rather than sect. Pleuranthesis . Conclusions This study reports 14 complete chloroplast genomes of Zingiber species. Overall, this study provided a solid backbone phylogeny of Zingiber . The polymorphisms we have uncovered in the sequencing of the genome offer a rare possibility (for Zingiber ) of the generation of DNA markers. These results provide a foundation for future studies that seek to understand the molecular evolutionary dynamics or individual population variation in the genus Zingiber .

The complete chloroplast genome of Artemisia annua (Asteraceae), the primary source of artemisinin, was sequenced and analyzed. The A. annua cp genome is 150,995 bp, and harbors a pair of inverted repeat regions (IRa and IRb), of 24,850 bp each that separate large (LSC, 82,988 bp) and small (SSC, 18,267 bp) single-copy regions. Our annotation revealed that the A. annua cp genome contains 113 genes and 18 duplicated genes. The gene order in the SSC region of A. annua is inverted; this fact is consistent with the sequences of chloroplast genomes from three other Artemisia species. Fifteen (15) forward and seventeen (17) inverted repeats were detected in the genome. The existence of rich SSR loci in the genome suggests opportunities for future population genetics work on this anti-malarial medicinal plant. In A. annua cpDNA, the rps19 gene was found in the LSC region rather than the IR region, and the rps19 pseudogene was absent in the IR region. Sequence divergence analysis of five Asteraceae species indicated that the most highly divergent regions were found in the intergenic spacers, and that the differences between A. annua and A. fukudo were very slight. A phylogenetic analysis revealed a sister relationship between A. annua and A. fukudo. This study identified the unique characteristics of the A. annua cp genome. These results offer valuable information for future research on Artemisia species identification and for the selective breeding of A. annua with high pharmaceutical efficacy.

Main conclusion This study provides broad insight into the chloroplast genomes of the subfamily Monsteroideae. The identified polymorphic regions may be suitable for designing unique and robust molecular markers for phylogenetic inference. Monsteroideae is the third largest subfamily (comprises 369 species) and one of the early diverging lineages of the monocot plant family Araceae. The phylogeny of this important subfamily is not well resolved at the species level due to scarcity of genomic resources and suitable molecular markers. Here, we report annotated chloroplast genome sequences of four Monsteroideae species: Spathiphyllum patulinervum , Stenospermation multiovulatum , Monstera adansonii , and Rhaphidophora amplissima . The quadripartite chloroplast genomes (size range 163,335–164,751 bp) consist of a pair of inverted repeats (25,270–25,931 bp), separating a small single copy region (21,448–22,346 bp) from a large single copy region (89,714–91,841 bp). The genomes contain 114 unique genes, including four rRNA genes, 80 protein-coding genes, and 30 tRNA genes. Gene features, amino acid frequencies, codon usage, GC contents, oligonucleotide repeats, and inverted repeats dynamics exhibit similarities among the four genomes. Higher rate of synonymous substitutions was observed as compared to non-synonymous substitutions in 76 protein-coding genes. Positive selection was observed in seven protein-coding genes, including psbK , ndhK , ndhD , rbcL , accD , rps8 , and ycf2 . Our included species of Araceae showed the monophyly in Monsteroideae and other subfamilies. We report 30 suitable polymorphic regions. The polymorphic regions identified here might be suitable for designing unique and robust markers for inferring the phylogeny and phylogeography among closely related species within the genus Spathiphyllum and among distantly related species within the subfamily Monsteroideae. The chloroplast genomes presented here are a valuable contribution towards understanding the molecular evolutionary dynamics in the family Araceae.

Abstract Plant cells have two major organelles with their own genomes: chloroplasts and mitochondria. While chloroplast genomes tend to be structurally conserved, the mitochondrial genomes of plants, which are much larger than those of animals, are characterized by complex structural variation. We introduce TIPPo, a user-friendly, reference-free assembly tool that uses PacBio high-fidelity long-read data and that does not rely on genomes from related species or nuclear genome information for the assembly of organellar genomes. TIPPo employs a deep learning model for initial read classification and leverages k-mer counting for further refinement, significantly reducing the impact of nuclear insertions of organellar DNA on the assembly process. We used TIPPo to completely assemble a set of 54 complete chloroplast genomes. No other tool was able to completely assemble this set. TIPPo is comparable with PMAT in assembling mitochondrial genomes from most species but does achieve even higher completeness for several species. We also used the assembled organelle genomes to identify instances of nuclear plastid DNA (NUPTs) and nuclear mitochondrial DNA (NUMTs) insertions. The cumulative length of NUPTs/NUMTs positively correlates with the size of the nuclear genome, suggesting that insertions occur stochastically. NUPTs/NUMTs show predominantly C:G to T:A changes, with the mutated cytosines typically found in CG and CHG contexts, suggesting that degradation of NUPT and NUMT sequences is driven by the known elevated mutation rate of methylated cytosines. Small interfering RNA loci are enriched in NUPTs and NUMTs, consistent with the RdDM pathway mediating DNA methylation in these sequences.

Background Subtribe Swertiinae, a medicinally significant and highly speciose Subtribe of family Gentianaceae. Despite previous extensive studies based on both morphology and molecular data, intergeneric and infrageneric relationships within subtribe Swertiinae remain controversial. Methods Here, we employed four newly generated Swertia chloroplast genomes with thirty other published genomes to elucidate their genomic characteristics. Results The 34 chloroplast genomes were small and ranged in size from 149,036 to 154,365 bp, each comprising two inverted repeat regions (size range 25,069–26,126 bp) that separated large single-copy (80,432–84,153 bp) and small single-copy (17,887–18,47 bp) regions, and all the chloroplast genomes showed similar gene orders, contents, and structures. These chloroplast genomes contained 129–134 genes each, including 84–89 protein-coding genes, 37 tRNAs, and 8 rRNAs. The chloroplast genomes of subtribe Swertiinae appeared to have lost some genes, such as rpl33 , rpl2 and ycf15 genes. Comparative analyses revealed that two mutation hotspot regions ( accD-psaI and ycf1 ) could serve as effective molecular markers for further phylogenetic analyses and species identification in subtribe Swertiinae. Positive selection analyses showed that two genes ( ccsA and psbB ) had high Ka/Ks ratios, indicating that chloroplast genes may have undergone positive selection in their evolutionary history. Phylogenetic analysis showed that the 34 subtribe Swertiinae species formed a monophyletic clade, with Veratrilla , Gentianopsis and Pterygocalyx located at the base of the phylogenetic tree. Some genera of this subtribe, however, were not monophyletic, including Swertia , Gentianopsis , Lomatogonium , Halenia , Veratrilla and Gentianopsis . In addition, our molecular phylogeny was consistent with taxonomic classification of subtribe Swertiinae in the Roate group and Tubular group. The results of molecular dating showed that the divergence between subtrib Gentianinae and subtrib Swertiinae was estimated to occur in 33.68 Ma. Roate group and Tubular group in subtribe Swertiinae approximately diverged in 25.17 Ma. Conclusion Overall, our study highlighted the taxonomic utility of chloroplast genomes in subtribe Swertiinae, and the genetic markers identified here will facilitate future studies on the evolution, conservation, population genetics, and phylogeography of subtribe Swertiinae species.