In this study, we conducted an assembly and analysis of the organelle genomes of Aconitum carmichaelii. Our investigation encompassed the examination of organelle genome structures, gene transfer events, and the environmental selection pressures affecting A. carmichaelii. The results revealed distinct evolutionary patterns in the organelle genomes of A. carmichaelii. Especially, the plastome exhibited a more conserved structure but a higher nucleotide substitution rate (NSR), while the mitogenome displayed a more complex structure with a slower NSR. Through homology analysis, we identified several instances of unidirectional protein-coding genes (PCGs) transferring from the plastome to the mitogenome. However, we did not observe any events which genes moved from the mitogenome to the plastome. Additionally, we observed multiple transposable element (TE) fragments in the organelle genomes, with both organelles showing different preferences for the type of nuclear TE insertion. Divergence time estimation suggested that rapid differentiation occurred in Aconitum species approximately 7.96 million years ago (Mya). This divergence might be associated with the reduction in CO₂ levels and the significant uplift of the Qinghai-Tibet Plateau (QTP) during the late Miocene. Selection pressure analysis indicated that the dN/dS values of both organelles were less than 1, suggested that organelle PCGs were subject to purification selection. However, we did not detect any positively selected genes (PSGs) in Subg. Aconitum and Subg. Lycoctonum. This observation further supports the idea that stronger negative selection pressure on organelle genes in Aconitum results in a more conserved amino acid sequence. In conclusion, this study contributes to a deeper understanding of organelle evolution in Aconitum species and provides a foundation for future research on the genetic mechanisms underlying the structure and function of the Aconitum plastome and mitogenome.

The family Daphniphyllaceae has a single genus, and no relevant comparative phylogenetic study has been reported on it. To explore the phylogenetic relationships and organelle evolution mechanisms of Daphniphyllaceae species, we sequenced and assembled the chloroplast and mitochondrial genomes of Daphniphyllum macropodum. We also conducted comparative analyses of organelles in Daphniphyllaceae species in terms of genome structure, phylogenetic relationships, divergence times, RNA editing events, and evolutionary rates, etc. Results indicated differences in the evolutionary patterns of the plastome and mitogenome in D. macropodum. The plastome had a more conserved structure but a faster nucleotide substitution rate, and the mitogenome showed a more complex structure while the mitotic genome shows a more complex structure but a slower nucleotide substitution rate. We identified several unidirectional protein-coding gene transfer events from the plastome to the mitogenome based on homology analysis, but no transfer events occurred from the mitogenome to the plastome. Multiple TE fragments existed in organelle genomes, and two organelles showed different preferences for nuclear TE insertion types. The estimation of divergence time indicated that the differentiation of Daphniphyllaceae and Altingiaceae at around 29.86 Mya might be due to the dramatic uplift of Tibetan Plateau during the Oligocene. About 75% of codon changes in organelles were found to be hydrophilic to hydrophobic amino acids. The RNA editing in protein-coding transcripts is the result of amino acid changes to increase their hydrophobicity and conservation in alleles, which may contribute to the formation of functional 3D structures in proteins. This study would enrich genomic resources and provide valuable insights into the structural dynamics and molecular biology of Daphniphyllaceae species.

Introduction: The Zingiberaceae family, which includes numerous economically and medicinally important species, exhibits considerable phylogenetic and genetic diversity. Chloroplast genomes are valuable resources for studying evolutionary relationships, genetic diversity, and adaptive evolution in plants. While many Zingiberaceae chloroplast genomes have been sequenced, the evolutionary mechanisms—including structural variation, codon usage bias, selection pressures, and divergence history—remain to be comprehensively investigated. Methods: we performed a comparative analysis of 11 newly identified species (Aframomum alboviolaceum, Amomum longipetiolatum, Amomum petaloideum, Amomum velutinum, Cautleya spicata, Cornukaempferia larsenii, Globba atrosanguinea, Globba variabilis, Hedychium aureum, Riedelia arfakensis, and Zingiber citriodorum) and 110 published data from the Zingiberaceae family, including their structure, codon usage, nucleotide polymorphisms, divergence time, and selection pressures.Results: The chloroplast genomes of Zingiberaceae species exhibited a highly conserved structure with no significant expansion or contraction during diversification. Analysis revealed four hypervariable protein-coding genes (atpH, rpl32, ndhA, and ycf1) and one intergenic region (psac-ndhE), which are proposed as potential molecular markers for future phylogeographic and population genetic studies. Codon usage bias was found to be predominantly shaped by natural selection. Phylogenetic analysis strongly supported the division of Zingiberaceae into two primary subfamilies (Alpinioideae and Zingiberoideae) and clarified key relationships, revealing that Globba is more closely related to Curcuma than to Hedychium, and Hedychium is more closely related to the Pommereschea-Rhynchanthus clade than to Cautleya. Divergence time estimation indicated two rapid diversification events within Zingiberoideae, coinciding with the rapid uplift of the Tibetan Plateau and a Late Miocene cooling event linked to declining CO₂ levels. Ancestral range reconstruction suggested an African origin during the Cretaceous period, followed by dispersal to Southeast Asia and India. Selection pressure analysis showed that most protein-coding genes are under negative selection. In contrast, the ycf2 gene was found to be under relaxed selection. Furthermore, two genes (matK and ndhB) were identified to be under positive selection in high-altitude species of Roscoea, suggesting a role in adaptation to alpine environments.Discussion: This study provides a comprehensive genomic analysis of the Zingiberaceae family, highlighting the conserved nature of chloroplast genome structure despite extensive diversification. The identified mutation hotspots present valuable tools for developing high-resolution markers for species identification and biogeographic studies. The phylogenetic results resolve longstanding uncertainties in the relationships among key genera. The inferred divergence times and ancestral range suggest that the evolutionary history of Zingiberaceae was significantly influenced by major geological and climatic events, notably the uplift of the Tibetan Plateau and global cooling in the Late Miocene. The prevalence of negative/purifying selection across most genes indicates strong evolutionary constraints to maintain core photosynthetic functions. The discovery of positively selected genes in high-altitude Roscoea species provides insights into adaptive evolution to environmental stressors. These findings offer foundational knowledge for future efforts in crop improvement, species identification, and the conservation of genetic diversity within the Zingiberaceae family.

The Meconopsis species are widely distributed in the Qinghai-Tibet Plateau, Himalayas, and Hengduan Mountains in China, and have high medicinal and ornamental value. The high diversity of plant morphology in this genus poses significant challenges for species identification, given their propensity for highland dwelling, which makes it a question worth exploring how they cope with the harsh surroundings. In this study, we recently generated chloroplast (cp) genomes of two Meconopsis species, Meconopsis paniculata (M. paniculata) and M. pinnatifolia, and compared them with those of ten Meconopsis cp genomes to comprehend cp genomic features, their phylogenetic relationships, and what part they might play in plateau adaptation. These cp genomes shared a great deal of similarities in terms of genome size, structure, gene content, GC content, and codon usage patterns. The cp genomes were between 151,864 bp and 154,997 bp in length, and contain 133 predictive genes. Through sequence divergence analysis, we identified three highly variable regions (trnD-psbD, ccsA-ndhD, and ycf1 genes), which could be used as potential markers or DNA barcodes for phylogenetic analysis. Between 22 and 38 SSRs and some long repeat sequences were identified from 12 Meconopsis species. Our phylogenetic analysis confirmed that 12 species of Meconopsis clustered into a monophyletic clade in Papaveraceae, which corroborated their intrageneric relationships. The results indicated that M. pinnatifolia and M. paniculata are sister species in the phylogenetic tree. In addition, the atpA and ycf2 genes were positively selected in high-altitude species. The functions of these two genes might be involved in adaptation to the extreme environment in the cold and low CO₂ concentration conditions at the plateau.

In this study, we performed a comparative analysis based on a total of 255 spider mitogenomes and four outgroups, of which the mitogenomes of 39 species were assembled de novo, to explore the phylogenetic relationships and the adaptive evolution of mitogenomes. Results showed that Argyroneta aquatica had the longest mitochondrial length and the most pronounced codon preference to be UUA, followed by CCU. Codon usage frequencies were similar between families and codon usage in the mitogenome of spiders was mainly influenced by natural selection pressures rather than G/C mutation bias. Our phylogenetic topology clearly explained the evolutionary relationships among the spiders, and divergence time estimates indicated that the spiders originated in the early Devonian, and that the two clades of Mesothelae and Opisthothelae separated in the late Carboniferous. Ancestral range and trait reconstruction results supported the ancestral origin of spiders to the Devonian Nearctic realm, with the trapdoor being the original trait. Selection analysis detected positive selection signals in the ATP8 gene in Desis jiaxiangi. The ND5 gene is a convergent evolutionary gene between D. jiaxiangi and A. aquatica. Positive selection signals in the ATP8 gene and convergent selection sites in the ND5 gene may facilitate metabolic adaptation to the aquatic environment in two aquatic spiders. In conclusion, our analysis contributes to a better understanding of the taxonomic status, species diversity, mitochondrial characteristics, and environmental adaptations of these spiders.

Carex breviculmis is a perennial herb with good resistance and is widely used for forage production and turf management. We assembled the genome of 469.01 Mb, revealing 37,372 genes with a BUSCO completeness score of 99.0%. The genome comprises 52.03% repetitive sequences, primarily influenced by recent LTR insertions that have contributed to its expansion. Phylogenetic analysis suggested that C. breviculmis diverged from C. littledalei approximately 6.61 Mya. Investigation into repetitive sequences and expanded gene families (EGFs) highlighted a rapid expansion of tandem duplicate (TD) genes, particularly in areas related to sugar metabolism, various amino acid synthesis, and phenylpropanoid biosynthesis. Additionally, our analysis identified crucial genes involved in secondary metabolic pathways such as glycolysis, phenylpropanoid biosynthesis, and amino acid metabolism, which have undergone positive selection. We reconstructed the sucrose metabolic pathway and identified significant gene expansions, included 16 INV, 9 SPS, and 12 SuSy genes associated with sucrose metabolism, showed varying levels of expansion. In summary, the expansion of these genes, coupled with subsequent positive selection, contributed to C. breviculmis' ability to adapt to environmental stressors. This study lays the foundation for future research on the evolution of Carex plants, their environmental adaptations, and potential genetic breeding.