The proliferation and differentiation of callus is the foundation for plant regeneration and propagation. The type of carbon sources in the medium significantly influences the efficacy of callus proliferation and differentiation in plants in vitro. Our study performed transcriptomic and physiological analyses utilizing sucrose, glucose, and maltose to understand the physiological and molecular characteristics of the proliferation and differentiation potential affected by carbon sources in Agapanthus praecox. Differentially expressed genes were notably associated with plant hormone signal transduction, glycolysis/gluconeogenesis, and MAPK signaling in the proliferation and differentiation of callus. The physiological indicators suggest glucose enhanced both callus and cell size by increasing endogenous indole-3-acetic acid (IAA), cytokinin, brassinosteroid, gibberellin (GAs), starch, and glucose levels, while concurrently reducing levels of reactive oxygen species (ROS) such as hydrogen peroxide (H₂O₂) and hydroxyl radical (·OH). Conversely, sucrose treatment promoted differentiation potential by elevating IAA oxidase activity alongside stress-related hormones such as abscisic acid and ethylene levels. Additionally, sucrose treatment led to increased accumulation of sucrose, fructose, H₂O₂, and ·OH within the callus tissue. Furthermore, sucrose influenced the regenerative capacity by modulating glycometabolism and osmoregulation. Our study posits that glucose facilitates callus proliferation via diminished ROS intensity while sucrose promotes callus differentiation by maintaining moderate ROS levels. Altogether, our results suggest carbon sources affected the regenerative capabilities of callus by regulating plant hormone signal and ROS intensity in A. praecox.

Acalypha hispida Burm. f. (1768) is an evergreen shrub native to New Guinea and the Bismarck Archipelago. Currently, it is widely cultivated as an ornamental and medicinal plant in tropical and subtropical areas worldwide. This study characterized the complete chloroplast genome of A. hispida, which is 172,122 bp in length and consists of large single-copy (LSC) and small single-copy (SSC) regions of 97,025 bp and 19,787 bp, respectively, that are separated by a pair of 27,655 bp inverted repeat (IR) regions. The overall GC content of the genome is 34.22%. The genome contains 131 genes, including 86 protein-coding, 37 tRNA, and eight rRNA genes. Phylogenetic analysis indicates that A. hispida is closely related to Ricinus communis and Cleidiocarpon cavaleriei in the Euphorbiaceae family. The complete chloroplast genome of A. hispida provides genomic resources and potential markers suitable for future species identification and speciation studies of the genus Acalypheae and will also provide important information on the phylogenetic relationships of the Euphorbiaceae family.

Callus induction is the foundation for large-scale and rapid plant propagation, and explant age is a key factor affecting callus induction efficiency and in vitro culture outcomes. Pedicels are the main explants for Agapanthus praecox tissue culture. This study analyzed three pedicel developmental stages (S1: immature, S2: semi-mature, S3: mature) and their induced calli (C1, C2, C3). We integrated transcriptomics, metabolomics (LC-MS/GC-MS), quantitative real-time PCR (qRT-PCR), and weighted gene co-expression network analysis (WGCNA) to clarify the physiological and molecular mechanisms of pedicel regenerative potential. Results showed that S2 exhibited the highest callus induction rate, while C2 showed superior proliferation coefficients and regenerative potential. In pedicel samples, differentially expressed genes were significantly enriched in the MAPK signaling pathway and plant hormone signal transduction pathway, while differentially accumulated metabolites were linked to energy metabolism, amino acid/nucleotide metabolism, and stress responses. Key metabolites (e.g., carbohydrates, amino acids, thidiazuron, and β-chlorogenin) played specific roles in maintaining the meristematic capacity of pedicels. qRT-PCR further confirmed that S2 maintained balanced endogenous hormone signaling and proper cell wall modification. Furthermore, WGCNA identified a key module associated with oxidative stress responses along with S2. Overall, the regenerative potential of pedicel is mediated by the balanced hormone signal transduction, metabolic reprogramming, and epigenetic regulation in A. praecox.

Background: Pachystachys lutea Nees is a typical species of the family Acanthaceae, native to tropical South America. As an evergreen shrub, it has found extensive application in landscape greening due to its unique ornamental value. However, there are currently no phylogenetic and genetic studies on the chloroplast (cp.) genome of P. lutea . Results: This study characterized the cp. genome of P. lutea using high-throughput sequencing technology and analyzed its structural features and phylogenetic position using bioinformatics methods. The results indicated that the cp. genome had a high degree of conservation in gene structure and gene content, with a typical quadripartite structure. Its total length is 151,574 bp and the total GC content is 38.18%. A total of 132 genes were annotated, including 87 protein-coding genes (PCGs), 37 tRNAs and eight rRNA genes. Through the comparative analysis, the diversity and variation of large single-copy (LSC) and small single-copy (SSC) regions were significantly higher than those of inverted repeat (IR) regions. Genes with high nucleotide polymorphism, such as rps19 , ycf1 , and ndhF provided potential reference loci for molecular identification within the P. lutea . The phylogenetic analysis showed that the P. lutea and Clinacanthus nutans forms a sister group with 100% bootstrap value, which proves that P. lutea develops conservatively in the course of evolution. Conclusion: This paper for the first time reports the phylogenetic study of the complete cp. genome within the genus Pachystachys . The study provides a theoretical basis for the research on genetic diversity, molecular markers, and species identification of plants in the Acanthaceae family. It enriches the genetic information and supports the evolutionary relationships among plants in this family.

Physostegia virginiana (L.) Benth. (1930) is an ornamental plant with great potential for landscaping application and cut-flower using in China. To explore its phylogenetic position and analyze the characteristics of its chloroplast (cp) genome, this study sequenced the whole cp genome of P. virginiana. The results revealed that the total length of the cp genome was 152,880 bp, and the lengths of the large single-copy region (LSC) and small single-copy region (SSC) were 84,428 and 17,396 bp, respectively. The lengths of the inverted repeat regions (IRa and IRb) were both 25,528 bp. The cp genome of P. virginiana contains 131 coding genes, namely, 86 protein-coding genes, 37 tRNA genes and eight rRNA genes. The total GC content of the cp genome was 38.38%. The phylogenetic results revealed that P. virginiana was closely related to Gomphostemma lucidum. The results of this study provide a molecular basis for the phylogenetic localization of P. virginiana and basic data for its identification and resource development.

Background: Penstemon, a core genus of the tribe Cheloneae in Plantaginaceae, possesses significant ecological and horticultural value. However, its interspecific phylogenetic relationships remain unclear due to morphological convergence, hybridization events, and limited genomic resources. This study aimed to characterize the complete chloroplast (cp) genome of Penstemon digitalis and explore its genomic features and phylogenetic position within Plantaginaceae. Methods: We sequenced the cp genome of P. digitalis using high-throughput sequencing, assembled and annotated the genome, and compared it with other Plantaginaceae species. Repetitive sequences and hypervariable regions were identified. Phylogenetic analyses were performed using maximum likelihood (ML) based on complete cp genomes from 46 taxa (36 Plantaginaceae, six Scrophulariaceae, and four outgroup species). Results: The cp genome is 152,993 bp with a typical quadripartite structure, containing 132 functional genes (87 protein-coding, 37 tRNA, and eight rRNA). Comparative analyses showed high gene content and structural conservation within the tribe Cheloneae. Several hypervariable regions and repeats were detected as potential markers. ML analysis strongly supported the monophyly of Penstemon among the sampled species (100% bootstrap) and placed P. digitalis in a well-supported clade within the genus; Penstemon was recovered as the sister group of Russelia equisetiformis. Conclusions: This study provides the first complete cp genome resource for P. digitalis, confirming its phylogenetic affinity and offering valuable genomic data for future studies on population genetics, species delimitation, and adaptive evolution in Penstemon. These findings will aid taxonomic revision and conservation efforts for this diverse genus.