Lingjian Gui

Background: Parasitic and hemiparasitic plants exhibit highly variable mitochondrial genome structures and gene content, but the evolutionary processes underlying this variation remain incompletely understood. This study aimed to characterize the structural features, gene composition, and evolutionary characteristics of the complete mitochondrial genome of Taxillus chinensis. Results: The mitochondrial genome of T. chinensis exhibits a complex multipartite structure composed of multiple linear and circular DNA molecules. Fragmented synteny and heterogeneous genomic organization indicate substantial structural complexity. The genome contains abundant dispersed and palindromic repeats, including long repeat units, contributing to the complex repetitive landscape of the mitogenome. The mitogenome encodes 27 protein-coding genes and three rRNA genes, but only three tRNA genes, indicating substantial reduction of mitochondrial tRNA genes. All rpl genes are absent, indicating a substantial reduction of translation-related components. Homology searches against the nuclear genome and mitochondrial contigs identified only fragmented rpl-related sequences, which likely represent nonfunctional pseudogene remnants rather than intact functional genes. Ka/Ks analyses show that most mitochondrial protein-coding genes remain under strong purifying selection, although evolutionary rate heterogeneity is observed among functional categories. Conclusion: The mitochondrial genome of T. chinensis exhibits pronounced structural complexity and extensive loss of translation-related genes, while most retained mitochondrial protein-coding genes remain under strong purifying selection. These findings provide new insights into the structural evolution, functional reduction, and evolutionary constraints of mitochondrial genomes in hemiparasitic plants.

Taxillus chinensis (DC.) Danser is an important hemiparasitic medicinal plant whose propagation is severely limited by the desiccation sensitivity of its recalcitrant seeds. Dehydrins (DHNs), which protect plants against dehydration-induced stresses such as salinity, drought, and low temperatures, may play a critical role in protecting recalcitrant seeds. However, the role of DHNs in the seeds of T. chinensis remains unclear. In this study, a differentially expressed gene was identified from the seed transcriptome of T. chinensis and designated TcDHN1. Sequence alignment and phylogenetic analyses revealed that TcDHN1 encodes a dehydrin protein. Heterologous overexpression of TcDHN1 in Arabidopsis did not affect growth under normal conditions. Under salt, drought, and cold stresses, transgenic lines exhibited higher seed germination rates, longer primary roots, and improved seedling growth compared with wild-type (WT) plants. The transgenic lines showed significantly increased activities of antioxidant enzymes, including superoxide dismutase, catalase, and peroxidase. In addition, ectopic overexpression of TcDHN1 in Arabidopsis conferred enhanced tolerance to abiotic stresses compared to WT plants, accompanied by increased expression of the stress-responsive genes Responsive to Desiccation 29A (AtRD29A) and Heat Shock Protein 70-1 (AtHSP70-1). The above results indicate that TcDHN1 confers enhanced tolerance to abiotic stresses. This study provides a functional characterization of an abiotic stress-responsive gene from recalcitrant seeds and identifies a potential genetic resource for molecular breeding. This could potentially improve abiotic stress resistance in T. chinensis and related medicinal plants.

As an early-diverging angiosperm lineage, Chloranthaceae produces specialized coumarins with documented antimicrobial and anti-inflammatory activities, which contribute to its ecological success. Isofraxidin, the most representative simple coumarin in this clade, exhibits significant pharmaceutical potential. However, its biosynthetic basis remains uncharacterized. Here, we assembled a high-quality triploid genome of Chloranthus sp icatus (8.57 Gb, contig N50 = 8.76 Mb) to explore the evolution of defensive metabolism. Genomic analysis revealed an ancient whole-genome duplication event and expanded gene families associated with pathogen resistance. Metabolomic analysis identified at least 49 coumarin compounds in Chloranthus plants, significantly exceeding previous records. Integrated omics revealed 267 candidate biosynthetic genes across 9 enzyme families governing isofraxidin biosynthesis. Building on the upstream synthesis of the phenylpropanoid backbone, this study identifies amplified coumarin synthase (COSY) genes linked to umbelliferone accumulation, and specific CYP450s and O-methyltransferases catalyzing final structural modifications. This work elucidates the evolution of chemical defenses in early angiosperms and enables the engineering of plant-derived antimicrobials.

Tongoloa is a herbaceous genus of East Asia Clade (Apiaceae) distributed in the alpine regions. The use of DNA fragments has not provided a well‐resolved evolutionary history. For this research, we primarily collected samples from the type localities of Tongoloa and closely related taxa in the Hengduan Mountains. The chloroplast (cp) genomes and nuclear ribosomal (nr) DNA repeats of 27 taxa were assembled using genome skimming sequencing reads. We analyzed the characteristics of the Tongoloa cp genome, and found a remarkable expansion of the Inverted Repeats. Three genes (ndhC, ndhJ, and petG) related to photosynthesis appear to have undergone significant selective pressure. Through high‐resolution phylogenetic analysis, the cpDNA provided compelling evidence supporting the inclusion of Sinolimprichtia as an early taxon within Tongoloa. However, the nrDNA suggested that Tongoloa and Sinolimprichtia belong to distinct branches. Morphological analysis showed that Tongoloa has broadly oval fruits with a cordate base, whereas the fruits of Sinolimprichtia are long‐obovate with an obtuse base. The specific fruit morphology of Sinolimprichtia was found to be nested within Tongoloa in the cpDNA phylogenetic tree. Ancient introgression and chloroplast capture provide the most plausible explanation for the significant conflict between the nrDNA and cpDNA phylogenies. Our study highlights the potential impact of the complex evolutionary history of Tongoloa on the challenges encountered in previous taxonomic treatments.

We identified and described Cortiella yatungense, a new species of Cortiella (Apiaceae) from Xizang, China. This species can be distinguished from other members of this genus (C. hookeri, C. caespitosa, C. lamondiana, and C. cortioides) by fewer umbels (3–6), thinner and longer pedicels than the leaves, ovate to suborbicular fruits, and mericarp without vittae. Molecular phylogenetic analyses based on the internal transcribed space (ITS) region and two chloroplast DNA intron sequences (rpl16 and rps16) showed that C. yatungense was sister to C. hookeri with strong support. Thus, both morphological and phylogenetic evidence suggested that C. yatungense is a distinct species of Cortiella. A comprehensive description of C. yatungense along with morphological characteristics and habitat are provided.

Cinnamomum cassia Presl is widely known as an important aroma and medicinal tree species growing in tropical and subtropical regions of Asia. The complete chloroplast genome of C. cassia which is 152,763 bp in length was determined. A total of 126 genes were detected in the chloroplast genome, including 36 tRNA genes, 8 rRNA genes, and 82 CDS. The total number of SSRs in this genome is 157. Phylogenetic analysis of this species based on 51 shared chloroplast CDS is provided. These results will provide useful resources for the study of molecular phylogeny and genetics of C. cassia. Bangladesh J. Bot. 51(1): 51-55, 2022 (March)

Sinocarum muliense (Apiaceae), is proposed as a new species from Sichuan, southwest China. It is most similar to S. cruciatum var. linearilobum , but can be distinguished by having globose (versus torulos) roots, ultimate segments of blade 8.0–30.0 × 0.3–1.2 mm (versus 5–20 × 1–2 mm), purple (versus greenish‐white) petals with acute (versus obtuse) apex.

Plumeria rubra cv. Acutifolia is a widely planted landscape tree in the subtropics. In this study, the complete chloroplast genome of P. rubra cv. Acutifolia was determined through Illumina sequencing method. The complete chloroplast genome has a length of 153,912 bp, containing a small single-copy region (18,036 bp), a large single-copy region (84,852 bp), and a pair of IR regions (25,512 bp). The chloroplast genome possesses 130 genes, including 85 CDS, 37 tRNA genes and 8 rRNA genes. P. rubra cv. Acutifolia exhibited the closest relationship with P. cubensis in phylogenetic analysis.

Archontophoenix alexandrae, known as king palm, is an important landscape tree for the subtropics and potential sources of dietary fiber. In this study, the complete chloroplast genome of A. alexandrae was determined through Illumina sequencing method. The chloroplast genome was 159,196 bp in length and contained a small single-copy region (17,763 bp), a large single-copy region (87,055 bp) and a pair of IR regions (27,189 bp). 135 genes were determined in the A. alexandrae chloroplast genome, including 86 CDS, 39 tRNA genes, and 8 rRNA genes. Archontophoenix alexandrae showed the closest relationship with Veitchia arecina in the phylogenetic analysis.