Comparative analysis of the complete chloroplast genome of Papaveraceae to identify rearrangements within the Corydalis chloroplast genome

Comparison of the Complete Chloroplast Genomes of Astilbe: Two Korean Endemic Plant Species

BACKGROUND

Astilbe, consisting of about 18 species, is distributed throughout East Asia and Northeastern America, and most Astilbe species are widely cultivated as ornamental plants. A total of four species of Astilbe have been confirmed to be distributed throughout Korea, two of which are endemic to Korea.

METHODS

In this study, we sequenced and assembled the complete chloroplast genomes of two endemic Korean plants using Illumina sequencing technology, identified simple sequence repeats (SSRs) and repetitive sequences, and compared them with three previously reported chloroplast genomes.

RESULTS

The chloroplast genomes of the two species were 156,968 and 57,142 bp in length and had a four-part circular structure. They consisted of a large single-copy region of 87,223 and 87,272 bp and a small single-copy region of 18,167 and 18,138 bp, separated by a pair of inverted repeats (IRa and IRb, 25,789 and 25,866 bp). The genomes contained 130 genes, 49 SSRs, and 49 long repetitive sequences. Comparative analysis with the chloroplast genomes of five Astilbe species indicated that A. uljinensis was closely related to A. chinensis and A. taquetii to A. koreana.

CONCLUSIONS

This study provides valuable references for the identification of two endemic Korean Astilbe species and contributes to a deeper understanding of the phylogeny and evolution of the genus Astilbe.

Complete Chloroplast Genome of Crassula aquatica: Comparative Genomic Analysis and Phylogenetic Relationships

BACKGROUND/OBJECTIVES

Crassula aquatica (L.) Schonl. is a very small annual plant growing along riverbanks. Chloroplast (cp) genomes, crucial for photosynthesis, are highly conserved and play a key role in understanding plant evolution. In this study, we conducted cp genome analysis of C. aquatica, aiming to elucidate its phylogenetic position and structural variations. We analyzed and described the features of the complete cp genome of C. aquatica and conducted comparative analysis with the cp genomes of closely related taxa.

RSULTS

The cp genome was 144,503 bp in length and exhibited the typical quadripartite structure, consisting of a large single-copy region (LSC; 77,993 bp), a small single-copy region (SSC; 16,784 bp), and two inverted repeats (24,863 bp). The cp genome of C. aquatica comprised 113 unique genes, including 79 protein-coding genes (PCGs), 30 tRNAs, and 4 rRNA genes. Comparative genomic analysis of 13 other Crassula species and six outgroups demonstrated highly conserved gene content and order among Crassula species. However, notable differences were observed, including the complete loss of the rpoC1 intron in C. aquatica and several closely related species, which may serve as a synapomorphic trait supporting the monophyly of the subgenus Disporocarpa. We analyzed the nucleotide diversity among 14 Crassula cp genomes and identified five highly variable regions (pi > 0.08) in the IGS regions. Phylogenetic analysis based on 78 PCGs confirmed the monophyly of Crassula and its division into two subgenera: Crassula and Disporocarpa. Although the phylogenetic tree supported the subgeneric classification system, the sectional classification system requires reassessment.

CONCLUSIONS

In this study, we conducted a comparative analysis of the cp genome of the genus Crassula. We inferred evolutionary trends within the Crassula cp genome and provided molecular evidence supporting the integration of the genus Tillaea into the genus Crassula. However, as this study does not represent all species within the genus Tillaea, further comprehensive phylogenetic analyses are requrired.

The Complete Chloroplast Genome of Meconopsis simplicifolia and Its Genetic Comparison to Other Meconopsis Species

Background: Chloroplasts, due to their high conservation and lack of recombination, serve as important genetic resources for the classification and evolutionary analysis of closely related species that are difficult to distinguish based on their morphological features. Meconopsis simplicifolia (M. simplicifolia), an endangered herb within the Meconopsis genus, has demonstrated therapeutic potential in treating various diseases. However, the highly polymorphic morphology of this species poses a challenge for accurate identification. Methods: In this study, the complete chloroplast genome of M. simplicifolia was sequenced and assembled using Illumina sequencing technology. Simple sequence repeats (SSRs) and repetitive sequences were characterized. In addition, a comparative analysis was conducted with the chloroplast genomes of six other Meconopsis species. Results: The chloroplast genome of M. simplicifolia has a quadripartite circular structure with a total length of 152,772 bp. It consists of a large single-copy region of 83,824 bp and a small single-copy region of 17,646 bp, separated by a pair of inverted repeat sequences (IRa and IRb, 25,651 bp). The genome contains 131 genes, 33 SSRs, and 27 long repetitive sequences. Comparative analysis with six other chloroplast genomes of Meconopsis revealed that M. simplicifolia is closely related to M. betonicifolia and that the rpl2 (ribosomal protein L2) gene in the IRb region has been deleted. This deletion is of significant importance for future taxonomic studies of M. simplicifolia. Conclusions: This study provides a valuable reference for the identification of M. simplicifolia and contributes to a deeper understanding of the phylogeny and evolution of the Meconopsis genus.

Deciphering the complete chloroplast genome sequence of Meconopsis torquata Prain: Insights into genome structure, comparative analysis and phylogenetic relationship

In the present study, we have characterized the complete chloroplast (Cp) genome of Meconopsis torquata Prain (family Papaveraceae), revealing the plastome size of 153,290 bp, and a GC content of 38.72 %. The cp genome features the typical circular quadripartite structure found in flowering plants, including a pair of inverted repeat regions (25,816 bp), isolated by a small single-copy region (17,740 bp) and a large single-copy (83,918 bp). Genome annotation revealed 132 genes: 87 protein-coding genes, 37 tRNAs and eight rRNAs. This comparative study demonstrated that the genome structure, gene number and GC ratio are consistent with several other cp genomes of Meconopsis and Papaver genera. A total of 120 SSRs were detected in the plastome, the majority (111) of which were mononucleotide repeats. Among the longer repeats, palindromic sequences were most common, followed by forward, reverse, and complement repeats. The whole genome alignment revealed the conserved nature of the inverted repeat region over single-copy zones. Nucleotide diversity unveiled hypervariable sites (ycf1, rps16, accD, atpB and psbD) in both the small and large single-copy regions, which could be useful for designing molecular markers for taxonomic identification. Phylogenetic analysis revealed a close alliance of M. torquata with other Meconopsis species, such as M. pinnatifolia and M. paniculata, with strong bootstrap support. Molecular dating suggests that M. torquata originated during the Tortonian age of the Miocene epoch of the Cenozoic era. These findings provide valuable insights for biological research, especially in understanding the genetic and evolutionary divergence within the Papaveraceae family.

Dynamic changes in the plastid and mitochondrial genomes of the angiosperm Corydalis pauciovulata (Papaveraceae)

BACKGROUND

Corydalis DC., the largest genus in the family Papaveraceae, comprises > 465 species. Complete plastid genomes (plastomes) of Corydalis show evolutionary changes, including syntenic arrangements, gene losses and duplications, and IR boundary shifts. However, little is known about the evolution of the mitochondrial genome (mitogenome) in Corydalis. Both the organelle genomes and transcriptomes are needed to better understand the relationships between the patterns of evolution in mitochondrial and plastid genomes.

RESULTS

We obtained complete plastid and mitochondrial genomes from Corydalis pauciovulata using a hybrid assembly of Illumina and Oxford Nanopore Technologies reads to assess the evolutionary parallels between the organelle genomes. The mitogenome and plastome of C. pauciovulata had sizes of 675,483 bp and 185,814 bp, respectively. Three ancestral gene clusters were missing from the mitogenome, and expanded IR (46,060 bp) and miniaturized SSC (202 bp) regions were identified in the plastome. The mitogenome and plastome of C. pauciovulata contained 41 and 67 protein-coding genes, respectively; the loss of genes was a plastid-specific event. We also generated a draft genome and transcriptome for C. pauciovulata. A combination of genomic and transcriptomic data supported the functional replacement of acetyl-CoA carboxylase subunit β (accD) by intracellular transfer to the nucleus in C. pauciovulata. In contrast, our analyses suggested a concurrent loss of the NADH-plastoquinone oxidoreductase (ndh) complex in both the nuclear and plastid genomes. Finally, we performed genomic and transcriptomic analyses to characterize DNA replication, recombination, and repair (DNA-RRR) genes in C. pauciovulata as well as the transcriptomes of Liriodendron tulipifera and Nelumbo nuicifera. We obtained 25 DNA-RRR genes and identified their structure in C. pauciovulata. Pairwise comparisons of nonsynonymous (dN) and synonymous (dS) substitution rates revealed that several DNA-RRR genes in C. pauciovulata have higher dN and dS values than those in N. nuicifera.

CONCLUSIONS

The C. pauciovulata genomic data generated here provide a valuable resource for understanding the evolution of Corydalis organelle genomes. The first mitogenome of Papaveraceae provides an example that can be explored by other researchers sequencing the mitogenomes of related plants. Our results also provide fundamental information about DNA-RRR genes in Corydalis and their related rate variation, which elucidates the relationships between DNA-RRR genes and organelle genome stability.

Extreme Reconfiguration of Plastid Genomes in Papaveraceae: Rearrangements, Gene Loss, Pseudogenization, IR Expansion, and Repeats

The plastid genomes (plastomes) of angiosperms are typically highly conserved, with extreme reconfiguration being uncommon, although reports of such events have emerged in some lineages. In this study, we conducted a comprehensive comparison of the complete plastomes from twenty-two species, covering seventeen genera from three subfamilies (Fumarioideae, Hypecooideae, and Papaveroideae) of Papaveraceae. Our results revealed a high level of variability in the plastid genome size of Papaveraceae, ranging from 151,864 bp to 219,144 bp in length, which might be triggered by the expansion of the IR region and a large number of repeat sequences. Moreover, we detected numerous large-scale rearrangements, primarily occurring in the plastomes of Fumarioideae and Hypecooideae. Frequent gene loss or pseudogenization were also observed for ndhs, accD, clpP, infA, rpl2, rpl20, rpl32, rps16, and several tRNA genes, particularly in Fumarioideae and Hypecooideae, which might be associated with the structural variation in their plastomes. Furthermore, we found that the plastomes of Fumarioideae exhibited a higher GC content and more repeat sequences than those of Papaveroideae. Our results showed that Papaveroideae generally displayed a relatively conserved plastome, with the exception of Eomecon chionantha, while Fumarioideae and Hypecooideae typically harbored highly reconfigurable plastomes, showing high variability in the genome size, gene content, and gene order. This study provides insights into the plastome evolution of Papaveraceae and may contribute to the development of effective molecular markers.