Okra (Abelmoschus esculentus L. Moench) is an annual herbaceous plant belonging to the Malvaceae family. Its medicinal properties and edible value have attracted widespread scientific attention, yet its systematic taxonomy, evolution, and photosynthetic mechanisms warrant further investigation. Chloroplasts, specialized semi-autonomous organelles within green plants, possess their own genetic material and serve as an excellent source of genetic information. This study employed Illumina high-throughput sequencing technology to sequence the complete chloroplast genome of the cultivar ‘Gan Kui No. 1’. The complete chloroplast genome was determined to be 163,121 bp in length, with A, C, G, T, and GC nucleotides accounting for 31.24%, 18.71%, 18.02%, 32.02%, and 36.74% of the total, respectively. It exhibits a classic tetrad structure, comprising one large single-copy region (88,071 bp), one small single-copy region (19,032 bp), and one pair of inverted repeat regions (28,009 bp). The entire chloroplast genome contains 132 annotated genes, including 37 tRNA genes, 8 rRNA genes, 87 mRNA genes, and 0 pseudogenes. A phylogenetic tree constructed using 20 species, including Abelmoschus esculentus, revealed a clear phylogenetic relationship between the genus Hibiscus and Abelmoschus esculentus. The complete gene sequences have been uploaded to the NCBI database (accession number PX590535). This study provides insights into understanding the evolutionary relationships of Abelmoschus esculentus and refining its taxonomy, laying a theoretical foundation for subsequent research on the Abelmoschus esculentus chloroplast genome.

Background: The chloroplast genome provides rich genetic information for plant evolutionary studies. This study aimed to assemble, annotate, and analyze the complete chloroplast genome of flax cultivar ‘Longya 15’ (Linum usitatissimum L.) and clarify its phylogenetic relationships with other Linaceae species. Methods: We assembled and annotated the chloroplast genome of ‘Longya 15’ and retrieved chloroplast genomes of related species (e.g., Linum grandiflorum NC_058845.1, Linum lewisii NC_058799.1) from the NCBI database for phylogenetic analysis. Results: The chloroplast genome of ‘Longya 15’ was a 157,074-bp quadripartite structure with 37.42% GC content, encoding 128 genes (83 mRNAs, 37 tRNAs, 8 rRNAs) without pseudogenes. It showed codon bias for leucine (28 codons with RSCU > 1, ending in A/U), 260 dispersed repeats, and 240 SSRs. Ka/Ks analysis revealed purifying selection for most genes, while rps18 and ycf2 had positive selection. ycf1 was identified as the hypervariable region (pi = 0.25024). Phylogenetically, it clustered closest with Linum grandiflorum, followed by L. lewisii and L. perenne, and was related to Hypericum species. Conclusions: This is the first fine assembly and annotation of ‘Longya 15’ chloroplast genome, confirming no pseudogenes in flax chloroplast. It elucidates flax chloroplast genome conservation and evolutionary dynamics, enriches the database, and provides a foundation for Linaceae phylogenetics, germplasm development, and stress-resistant breeding.

Background: Kenaf (Hibiscus cannabinus L.) is an important fiber crop belonging to the genus Hibiscus in the Malvaceae family. Research on its chloroplast genome holds significant importance for deciphering the evolutionary relationships of the Hibiscus species, developing genetic markers, and promoting kenaf (H. cannabinus) genetic breeding. Methods: Based on high-throughput sequencing technology, this study completed the sequencing and assembly of the kenaf (H. cannabinus) chloroplast genome. Results: (1) The kenaf (H. cannabinus) chloroplast genome exhibits a typical circular quadripartite structure with a total length of 163,019 bp, including a large single-copy region (LSC) of 90,467 bp, a small single-copy region (SSC) of 19,486 bp, and a pair of inverted repeat regions (IRa/IRb) of 26,533 bp each. The total GC content is 36.62%, among which, the IR region has the highest GC content (42.61%) and the SSC region the lowest (30.87%). (2) A total of 131 genes were annotated, including 85 mRNAs, 37 tRNAs, 8 rRNAs, and 1 pseudogene. Their functions cover photosynthesis (e.g., pet and atp family genes), self-replication (e.g., rpl, rps, and rpo family genes), and genes with unknown functions (e.g., ycf1 and ycf2). A codon usage bias analysis revealed that the relative synonymous codon usage (RSCU) value of the stop codon UAA is the highest (1.6329), and codons ending with A/U are preferentially used (e.g., GCU for alanine with RSCU = 1.778). (3) A repeat sequence analysis identified various interspersed repeat sequences (predominantly 30~31 bp in length, with a relatively high proportion in the 30~40 bp range, including forward and palindromic types) and simple sequence repeats (cpSSRs). Among them, single-base repeat SSRs account for the highest proportion (e.g., (A)8 and (T)9), and specific SSR primers were designed. (4) A comparative evolutionary analysis indicated that the Ka/Ks ratios (nonsynonymous substitution rate/synonymous substitution rate) of core chloroplast genes (e.g., rps2 and rpoC2) in kenaf (H. cannabinus) are all less than 1 (0.145~0.415), suggesting that they are under purifying selection. The collinearity similarity of chloroplast genomes between kenaf (H. cannabinus) and its closely related species reaches over 99.97%, and the IR region boundaries are relatively conserved. The phylogenetic tree shows that kenaf (H. cannabinus) clusters with closely related Hibiscus species with a 100% bootstrap value, indicating a close genetic relationship. Conclusions: This study provides basic data for the functional analysis of the kenaf (H. cannabinus) chloroplast genome, the phylogeny of Hibiscus, and the utilization of genetic resources.

Yeyong mustard is a mustard vegetable belonging to the Brassicaceae family and the Brassica genus. This study assembled, annotated, and analyzed the chloroplast genome of Brassica juncea L., aiming to clarify its systematic evolutionary relationship with other cruciferous plants. The study used the Illumina NovaSeq 6000 platform to sequence the entire chloroplast genome of leaf mustard, and systematically analyzed its genome structure, repeat sequences, nucleic acid diversity, and codon preferences using bioinformatics methods. At the same time, the phylogenetic relationships were constructed by combining the leaf chloroplast genome sequences of other cruciferous plants. The results showed that the chloroplast genome of leaf mustard had a total length of 153,490 bp and a GC content of 36.36%, exhibiting a typical tetrad structure; a total of 132 coding genes were annotated, including 87 mRNA genes, 37 tRNA genes, and eight rRNA genes, and no pseudogenes were found. Codon preference analysis shows that leucine (Leu) has the highest frequency of use, with 32 codons having a relative synonymous codon usage (RSCU) greater than 1, mostly ending in A or U; there are 37 scattered repetitive sequences and 315 simple repetitive sequences in the genome. Ka/Ks analysis showed that the chloroplast genes of leaf mustard were subjected to purification selection as a whole, while genes such as nadhF and petD showed positive selection, which is speculated to be related to adaptive evolution. The results of the phylogenetic analysis further confirm that the chloroplast genome of leaf mustard has a typical tetrad structure and is relatively conserved. It is most closely related to mustard greens in terms of evolutionary relationship, followed by Brassica plants such as nori and turnip, and is also closely related to Brassica plants such as European rapeseed. This study elucidated the conservative characteristics and evolutionary patterns of the chloroplast genome in mustard leaves, providing theoretical support for the phylogenetic research of the Brassicaceae family and the development and utilization of germplasm resources.

Roselle (Hibiscus sabdariffa L.) is a plant rich in bioactive constituents, serving as a unique material for the food and beverage industry and therapeutic applications. Despite its significant utility, few studies have focused on the molecular breeding of the plant. Chloroplasts are organelles in plant cells with independent genetic information, making them ideal for investigating plant phylogeny and genetic evolution. In this study, the roselle breeding material ‘Zhe Xiao Luo 1’ was selected to assemble and analyze the entire chloroplast genome using the Illumina NovaSeq X Plus platform. The phylogenetic relationships between roselle and other species within Malvaceae family, particularly within the genus Hibiscus, were clarified. The results showed that the complete chloroplast genome of roselle was 162,428 bp in length, with nucleotide proportions of 31.14% (A), 18.73% (C), 18.01% (G), 32.12% (T), and 36.74% (GC). It exhibited a typical tetrad structure consisting of four segments: the large single copy (LSC) region (90,327 bp), the small single-copy (SSC) region (19,617 bp), and two inverted repeat sequences (IRa and IRb, each 26,242 bp). A total of 130 genes were identified, including 37 tRNA genes, 8 rRNA genes, and 85 mRNA genes, and no pseudogenes were detected. Phylogenetic analysis using 23 revealed a clear phylogenetic relationship between H. sabdariffa and H. esculentus (okra) among all tested species. Building on previous research, this study further explored the functional annotation of genes in the roselle chloroplast genome, as well as its codon preference, repetitive sequences, simple sequence repeats (SSR), Ka/Ks ratio, nucleotide diversity (pi) analysis, and boundary analysis. The complete gene sequences have been uploaded to the NCBI database (accession number PX363576). This study provides evidence for elucidating the phylogenetic relationships and taxonomic status of H. sabdariffa, laying a theoretical foundation for studies on molecular mechanism resolution and cultivar development.

To clarify the phylogenetic relationship between Abutilon theophrasti M. and other Malvaceae plants, the chloroplast genome of A. theophrasti was assembled, annotated, and analyzed. The complete chloroplast genome was sequenced using the Illumina NovaSeq 6000 platform. Bioinformatics methods were employed to systematically analyze its genomic structure, repetitive sequences, nucleic acid diversity, and codon preference. Additionally, a phylogenetic tree was constructed by integrating chloroplast genomic sequences from other Malvaceae species. The results showed that the chloroplast genome of A. theophrasti was 160,440 bp in length with a GC content of 36.89%, exhibiting a typical tetrad structure. A total of 130 coding genes were annotated, including 85 mRNA genes, 37 tRNA genes, and 8 rRNA genes, with no pseudogenes detected. Codon preference analysis indicates that leucine (Leu) is the most frequently used amino acid. There are 31 codons with a relative synonymous codon usage (RSCU) value greater than 1, most of which end with A or U. The genome contains 61 scattered repeat sequences and 288 simple repeat sequences (SSR). Ka/Ks analysis revealed that the overall chloroplast genes of A. theophrasti undergo purifying selection, while genes such as psbK and rps12 are subjected to positive selection, which may be associated with adaptive evolution. Phylogenetically, A. theophrasti is most closely related to its congener A. indicum, followed by a clade comprising M. cathayensis and Malva crispa of the genus Malva. This study enhances the understanding of the phylogenetic relationship of A. theophrasti and provides a theoretical basis for the genetic improvement and breeding strategies of A. theophrasti and other Malvaceae plants.