Somatic embryogenesis (SE) is an ideal model for plant cell totipotency. Transition from somatic cells to embryogenic cells is the key to SE. The poor frequency of embryogenic callus (EC) induction has limited the application of SE in many plants, such as Agapanthus praecox. We performed large-scale, quantitative proteomic and metabolomic analyses with different callus differentiation directions (SE and organogenesis) and stages (initial SE and repetitive SE) to better understand the morphological, physiological, and molecular characteristics of the acquisition of embryogenic ability in A. praecox. Integrated proteomic and metabolomic analyses suggested that callus differentiation direction was potentially regulated by pathways related to carbohydrate and energy metabolism (fatty acid metabolism, pyruvate metabolism, glycolysis/gluconeogenesis, pentose and glucuronate interconversions, starch and sucrose metabolism, galactose metabolism, carbon fixation pathways in prokaryotes, carbohydrate digestion and absorption, and fructose and mannose metabolism), chromatin accessibility and DNA methylation, reactive oxygen species responses and resistance (ascorbate and aldarate metabolism), and plant hormonal signaling. As a validation, we found that carbon source combination and plant hormone regulation in the culture medium significantly affected the acquisition of embryogenic ability, thereby inducing EC. Interestingly, plant hormonal signaling-related genes showed different expression patterns significantly when callus cultured with different carbon sources. Thus, our results suggested that energy supply and hormone signal transduction seemed to cooperatively contribute to the activation of embryogenic ability. Altogether, this study revealed valuable information regarding the molecular and biochemical changes that occurred during EC induction and provided valuable foundation for comprehensive understanding of the mechanisms associated with SE and organogenesis in A. praecox.

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.