The complete chloroplast genome of Secale sylvestre (Poaceae: Triticeae)

The First Complete Chloroplast Genome Sequence of Secale strictum subsp. africanum Stapf (Poaceae), the Putative Ancestor of the Genus Secale

Secale strictum ssp. africanum (synonym Secale africanum), a putative ancestor of the genus Secale, has been classified within Secale strictum, although recent phylogenetic studies suggest that it represents a distinct species. This study reports the first complete chloroplast genome of S. africanum, highlighting its structure, genetic composition, and phylogenetic relationships within Secale and related Triticiceae species. Phylogeny reconstruction based on the maximum-likelihood method reveals notable genetic similarity between S. strictum and S. africanum, supporting their genetic and phylogenetic distinction. Here, we assembled the complete, annotated chloroplast genome sequence of Secale strictum ssp. africanum. The genome is 137,068 base pair (bp) long. It is the first complete chloroplast genome that can be used as a reference genome for further analysis. The genome can be accessed on GenBank with the accession number OQ700974. This work sheds light on the evolutionary history of Secale and contributes to our understanding of chloroplast genomics in cereal ancestors, with potential applications in improving cereal crop resilience, advancing breeding strategies, and informing conservation efforts for genetic diversity.

Comparative plastomes sheds light on phylogeny of Weigela

Weigela Thunb. is a genus in the family Caprifoliaceae. All species in this genus have high ornamental and medicinal value. However, the genetic divergence between species and the phylogeny within Weigela is still unclear. Therefore, we sequenced and analyzed four plastomes from four different Weigela species to reveal the genetic divergence among species of this genus, and the phylogeny within Weigela. The four plastomes from Weigela ranged from 156,909 bp to 157,739 bp in size, and presented a typical circular quadripartite structure. Each complete plastome contained a pair of inverted repeat regions (23,592~24,957 bp), a larger single-copy (LSC) region (89,922~90,229 bp), and a small single-copy (SSC) region (17,668~20,429 bp). We identified three types of repeats, corresponding to 268 forward repeats, 128 palindromic repeats, and 867 tandem repeats, for a total of 1,263 long repeats. A total of 352 SSRs were identified from the four plastomes, and most of them were concentrated in the LSC region and the noncoding regions. Mononucleotide repeat units were the most frequently detected types of repeats, of which A/T repeat units were the most abundant. Three mutational hotspots (trnH-psbA, trnR-ndhF, and trnN-ndhF) were identified as candidate barcodes for Weigela species. Weigela belongs to Diervilloideae located at an early diverging position in the Caprifoliaceae. Within Weigela, W. japonica and W. floribunda were sister with W. subsessilis and W. florida. This study revealed the plastome structure and variation of four well-known Weigela species, and found three candidate barcodes for further study of four well-known Weigela species. In addition, the phylogenetic location of Weigela within the Caprifoliaceae was identified.

The Complete Mitochondrial Genome of Paeonia lactiflora Pall. (Saxifragales: Paeoniaceae): Evidence of Gene Transfer from Chloroplast to Mitochondrial Genome

Paeonia lactiflora (P. lactiflora), a perennial plant renowned for its medicinal roots, provides a unique case for studying the phylogenetic relationships of species based on organelle genomes, as well as the transference of DNA across organelle genomes. In order to investigate this matter, we sequenced and characterized the mitochondrial genome (mitogenome) of P. lactiflora. Similar to the chloroplast genome (cpgenome), the mitogenome of P. lactiflora extends across 181,688 base pairs (bp). Its unique quadripartite structure results from a pair of extensive inverted repeats, each measuring 25,680 bp in length. The annotated mitogenome includes 27 protein-coding genes, 37 tRNAs, 8 rRNAs, and two pseudogenes (rpl5, rpl16). Phylogenetic analysis was performed to identify phylogenetic trees consistent with Paeonia species phylogeny in the APG Ⅳ system. Moreover, a total of 12 MTPT events were identified and 32 RNA editing sites were detected during mitogenome analysis of P. lactiflora. Our research successfully compiled and annotated the mitogenome of P. lactiflora. The study provides valuable insights regarding the taxonomic classification and molecular evolution within the Paeoniaceae family.

Complete chloroplast genomes of three wild perennial Hordeum species from Central Asia: genome structure, mutation hotspot, phylogenetic relationships, and comparative analysis

Hordeum L. is widely distributed in mountain or plateau of subtropical and warm temperate regions around the world. Three wild perennial Hordeum species, including H. bogdanii, H. brevisubulatum, and H. violaceum, have been used as forage and for grassland ecological restoration in high-altitude areas in recent years. To date, the degree of interspecies sequence variation in the three Hordeum species within existing gene pools is still not well-defined. Herein, we sequenced and assembled chloroplast (cp) genomes of the three species. The results revealed that the cp genome of H. bogdanii showed certain sequence variations compared with the cp genomes of the other two species (H. brevisubulatum and H. violaceum), and the latter two were characterized by a higher relative affinity. Parity rule 2 plot (PR2) analysis illuminated that most genes of all ten Hordeum species were concentrated in nucleotide T and G. Numerous single nucleotide polymorphism (SNP) and insertion/deletion (In/Del) events were detected in the three Hordeum species. A series of hotspots regions (tRNA-GGU ~ tRNA-GCA, tRNA-UGU ~ ndhJ, psbE ~ rps18, ndhF ~ tRNA-UAG, etc.) were identified by mVISTA procedures, and the five highly polymorphic genes (tRNA-UGC, tRNA-UAA, tRNA-UUU, tRNA-UAC, and ndhA) were proved by the nucleotide diversity (Pi). Although the distribution and existence of cp simple sequence repeats (cpSSRs) were predicted in the three Hordeum cp genomes, no rearrangement was found between them. A similar phenomenon has been found in the cp genome of the other seven Hordeum species, which has been published so far. In addition, evolutionary relationships were reappraised based on the currently reported cp genome of Hordeum L. This study offers a framework for gaining a better understanding of the evolutionary history of Hordeum species through the re-examination of their cp genomes, and by identifying highly polymorphic genes and hotspot regions that could provide important insights into the genetic diversity and differentiation of these species.

Molecular structure, comparative and phylogenetic analysis of the complete chloroplast genome sequences of weedy rye Secale cereale ssp. segetale

The complete chloroplast genome of Secale cereale ssp. segetale (Zhuk.) Roshev. (Poaceae: Triticeae) was sequenced and analyzed to better use its genetic resources to enrich rye and wheat breeding. The study was carried out using the following methods: DNA extraction, sequencing, assembly and annotation, comparison with other complete chloroplast genomes of the five Secale species, and multigene phylogeny. As a result of the study, it was determined that the chloroplast genome is 137,042 base pair (bp) long and contains 137 genes, including 113 unique genes and 24 genes which are duplicated in the IRs. Moreover, a total of 29 SSRs were detected in the Secale cereale ssp. segetale chloroplast genome. The phylogenetic analysis showed that Secale cereale ssp. segetale appeared to share the highest degree of similarity with S. cereale and S. strictum. Intraspecific diversity has been observed between the published chloroplast genome sequences of S. cereale ssp. segetale. The genome can be accessed on GenBank with the accession number (OL688773).