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.

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.