Ming Zhu

Background: Gynostemma pentaphyllum (Thunb.) Makino is an important medicinal plant within the Cucurbitaceae family. Despite its economic and pharmacological importance, genomic resources for this species remain limited. Methods: We sequenced and assembled the complete mitochondrial genome of G. pentaphyllum. Comparative analyses were conducted to investigate the genomic structure, gene content, RNA editing events, and intracellular gene transfer (IGT) from chloroplasts. Additionally, phylogenomic relationships, synteny, and the selective pressure on mitochondrial genes were evaluated against related species within Cucurbitaceae. Results: The ~324 kb mitogenome has a multipartite architecture of six circular-mapping molecules. It encodes the typical complement of mitochondrial protein-coding genes, tRNAs, and rRNAs found in angiosperms. Extensive C-to-U RNA editing, including events that generate functional start and stop codons, points to substantial post-transcriptional regulation. We also detected multiple chloroplast-derived fragments, including several intact genes, indicating active intracellular gene transfer. Phylogenomic analyses of conserved mitochondrial genes place G. pentaphyllum firmly within Cucurbitaceae, clustering it with Thladiantha cordifolia and Momordica charantia, whereas synteny comparisons reveal pronounced structural rearrangements with respect to these close relatives. While most genes evolve under strong purifying selection, rps1, sdh3, and sdh4 show signatures of accelerated evolution; furthermore, haplotype networks based on conserved loci further corroborate the close affinity with T. cordifolia. Conclusions: This study provides the first high-resolution mitogenome resource for G. pentaphyllum and candidate mitochondrial markers for species authentication, evolutionary studies, and breeding in Gynostemma and related cucurbits.

Megalurothrips usitatus is a global pest damaged legume crops, particularly cowpea (Vigna unguiculata). This study aimed to determine the chemical composition of lemongrass essential oil (LEO) and its insecticidal activity against the insect pest M. usitatus. The composition of lemongrass essential oil was analyzed using Gas Chromatography Mass Spectrometry (GC-MS). D-limonene, Neral, and Citral were found to constitute over 30% of the essential oil. LEO exhibited higher insecticidal toxicity than the individual pure components. Based on our results, the optimal formulation of LEO emulsifiable concentrates (ECs) was identified, and their insecticidal activity was further investigated. The mortality rate induced by the LEO did not significantly differ from that of the emamectin benzoate (EB) formulation but was lower than that of spinosad (SP). Additionally, LEO was shown to act as a synergist when combined with EB for controlling M. usitatus. This research offers an alternative strategy for controlling M. usitatus and reducing the reliance on synthetic pesticides.

Introduction: Spuriopimpinella brachycarpa (Kom.) Kitag., a member of the Apiaceae family, is a perennial aromatic herb native to Northeast Asia with applications in culinary and traditional medicine. Despite its significance, most studies on S. brachycarpa have primarily focused on its phytochemical properties, with limited insights into its molecular and genomic characteristics.Methods: This study presents the sequencing and assembly of the mitochondrial genome (mitogenome) of S. brachycarpa using second- and third-generation high-throughput sequencing technologies. Comprehensive analyses were performed on its structural organization, RNA editing sites, relative synonymous codon usage (RSCU), and repeat sequences. Comparative analyses with closely related species were also conducted.Results: The mitogenome exhibited a multi-branched structure, with a total length of 523,512 bp and a GC content of 43.37%. Annotation revealed 30 unique protein-coding genes, 21 tRNA genes, and three rRNA genes. Comparative analysis indicated that the S. brachycarpa mitogenome contains structural variations but shares collinear features with other Apiaceae species. We identified 618 potential RNA editing sites involving C-to-U conversions and discovered 59 homologous fragments between the mitogenome and plastome, comprising 8.13% of the mitogenome.Discussion: These results enrich the genomic database of Apiaceae, providing valuable insights into the evolutionary relationships and genetic diversity within the family.

The simple sequence repeats (SSRs) of plant chloroplasts show considerable genetic variation and have been widely used in species identification and phylogenetic relationship determination. Whether chloroplast genome SSRs can be used to classify Cyatheaceae species has not yet been studied. Therefore, the chloroplast genomes of eight Cyatheaceae species were sequenced, and their SSR characteristics were compared and statistically analyzed. The results showed that the chloroplast genome structure was highly conserved (genome size: 154,046–166,151 bp), and the gene content (117 genes) and gene order were highly consistent. The distribution characteristics of SSRs (number, relative abundance, relative density, GC content) showed taxon specificity. The primary results were the total numbers of SSRs and mononucleotides: Gymnosphaera (61–67 and 40–47, respectively), Alsophila (121–122 and 95–96), and Sphaeropteris (102–103 and 77–80). Statistical and clustering analyses of SSR characteristics showed that their distribution was consistent with the recent classification of Cyatheaceae, which divided the eight Cyatheaceae species into three genera. This study indicates that the distribution characteristics of Cyatheaceae chloroplast SSRs can provide useful phylogenic information at the genus level.

Recent taxonomic and molecular phylogenetic studies have shown that Gymnosphaera should be recognized as an independent taxonomic unit at the genus level under the family Cyatheaceae. In this study, the complete chloroplast genomes of the eight species of Cyatheaceae were sequenced, and their phylogenetic relationships were reconstructed using the maximum likelihood, Bayesian inference, maximum parsimony, and neighbor-joining methods, and the characteristics of their simple sequence repeats (SSRs) were compared and analyzed for the first time. The results showed that when Cyatheaceae was divided into three genera,the number, relative abundance, relative density, and GC content of all SSRs and of SSRs of certain unit lengths in the chloroplast genomes of the eight species of Cyatheaceae were genus specific in the whole chloroplast genomes and in their different regions (large single-copy, small single-copy, inverted repeat, intergenic spacer, intron, rRNA gene, and coding sequence regions). The SSRs overall and the single-nucleotide SSRs had significant differences in number, relative abundance, relative density, and GC content between the chloroplast genomes, their intergenic regions, and large single-copy regions. When Cyatheaceae was divided into two genera, only the difference in GC content was significant. Therefore, our results support the restoration of the hierarchical status of Gymnosphaera. This study provides an important basis for the identification of the phylogenetic relationship of Cyatheaceae plants.