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Abstract 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.

Abstract 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.

Abstract Background Seed germination is a series of ordered physiological and morphogenetic processes and a critical stage in plant life cycle. Tamarix hispida is one of the most salt-tolerant plant species; however, its seed germination has not been analysed using combined transcriptomics and metabolomics. Results Transcriptomic sequencing and widely targeted metabolomics were used to detect the transcriptional metabolic profiles of T. hispida at different stages of seed germination and young seedling growth. Transcriptomics showed that 46,538 genes were significantly altered throughout the studied development period. Enrichment study revealed that plant hormones, such as auxin, ABA, JA and SA played differential roles at varying stages of seed germination and post-germination. Metabolomics detected 1022 metabolites, with flavonoids accounting for the highest proportion of differential metabolites. Combined analysis indicated that flavonoid biosynthesis in young seedling growth, such as rhoifolin and quercetin, may improve the plant’s adaptative ability to extreme desert environments. Conclusions The differential regulation of plant hormones and the accumulation of flavonoids may be important for the seed germination survival of T. hispida in response to salt or arid deserts. This study enhanced the understanding of the overall mechanism in seed germination and post-germination. The results provide guidance for the ecological value and young seedling growth of T. hispida.