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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.

Chrysosplenium macrophyllum Oliv., belonging to the family Saxifragaceae, is a traditional and unique Chinese herbal medicine. However, the lack of adequate molecular markers has hampered the progress regarding population genetics and evolution within this species. In this research, we used the DNBSEQ-T7 Sequencer (MGI) sequencing assay to analyze the transcriptome profiles of C. macrophyllum. SSR markers were developed on the basis of transcriptomic sequences and further validated on C. macrophyllum and other Chrysosplenium species. The genetic diversity and structure of the 12 populations were analyzed by using polymorphic expressed sequence tag simple sequence repeat (EST-SSR) markers. A potential pool of 3127 non-redundant EST-SSR markers were identified for C. macrophyllum in this study. The developed EST-SSR markers had high amplification rates and cross-species transferability in Chrysosplenium. Our results also showed that the natural populations of C. macrophyllum had a high level of genetic diversity. Genetic distance, principal component analysis, and popular structure analysis revealed that all 60 samples clustered into two major groups that were consistent with their geographical origins. This study provided a batch of highly polymorphic EST-SSR molecular markers that were developed via transcriptome sequencing. These markers will be of great significance for the study of the genetic diversity and evolutionary history of C. macrophyllum and other Chrysosplenium species. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Summary: Safflower (Carthamus tinctorius L.), a member of the Asteraceae, is a popular crop due to its high linoleic acid (LA) and flavonoid (such as hydroxysafflor yellow A) contents. Here, we report the first high‐quality genome assembly (contig N50 of 21.23 Mb) for the 12 pseudochromosomes of safflower using single‐molecule real‐time sequencing, Hi‐C mapping technologies and a genetic linkage map. Phyloge nomic analysis showed that safflower diverged from artichoke (Cynara cardunculus) and sunflower (Helianthusannuus) approximately 30.7 and 60.5 million years ago, respectively. Comparative genomic analyses revealed that uniquely expanded gene families in safflower were enriched for those predicted to be involved in lipid metabolism and transport and abscisic acid signalling. Notably, the fatty acid desaturase 2 (FAD2) and chalcone synthase (CHS) families, which function in the LA and flavonoid biosynthesis pathways, respectively, were expanded via tandem duplications in safflower. CarFAD2‐12 was specifically expressed in seeds and was vital for high‐LA content in seeds, while tandemly duplicated CarFAD2 genes were up‐regulated in ovaries compared to CarFAD2‐12, which indicates regulatory divergence of FAD2 in seeds and ovaries. CarCHS1, CarCHS4 and tandem‐duplicated CarCHS5˜CarCHS6, which were up‐regulated compared to other CarCHS members at early stages, contribute to the accumulation of major flavonoids in flowers. In addition, our data reveal multiple alternative splicing events in gene families related to fatty acid and flavonoid biosynthesis. Together, these results provide a high‐quality reference genome and evolutionary insights into the molecular basis of fatty acid and flavonoid biosynthesis in safflower. [ABSTRACT FROM AUTHOR]