Somatic Embryogenesis in Centaurium erythraea Rafn-Current Status and Perspectives: A Review

Transcriptome and Gene Expression Analysis Revealed CeNA1: A Potential New Marker for Somatic Embryogenesis in Common Centaury (Centaurium erythraea Rafn.)

Centaurium erythraea Rafn. is a medicinal plant used as a model for studying plant developmental processes due to its developmental plasticity and ease of manipulation in vitro. Identifying the genes involved in its organogenesis and somatic embryogenesis (SE) is the first step toward unraveling the molecular mechanisms underlying its morphogenic plasticity. Although SE is the most common method of centaury regeneration, the genes involved in this have not yet been identified. The aim of this study was to identify the differentially expressed genes (DEGs) during key stages of SE and organogenesis using transcriptome data, with a focus on novel SE-related genes. The transcriptomic analysis revealed a total of 4040 DEGs during SE and 12,708 during organogenesis. Gene Ontology (GO) annotation showed that the highest number of SE-related genes was involved in defense responses. The expression of fifteen selected SE-related candidate genes was assessed by RT-qPCR across nine centaury developmental stages, including embryogenic tissues. Notably, a newly reported transcript, named CeNA1, was specifically activated during embryogenic callus (ec) induction, making it a potential novel marker for early SE. These findings provide, for the first time, insight into SE-related transcriptional patterns, representing a step closer to uncovering the molecular basis of centaury's developmental plasticity.

Dynamic changes of endogenous phytohormones and carbohydrates during spontaneous morphogenesis of Centaurium erythraea Rafn

Common centaury (Centaurium eryhtraea Rafn) is a medicinal plant species with vigorous morphogenic potential in vitro. The process of spontaneous shoot regeneration in a solid root culture is characteristic for this plant species. In this context, the aim of this work was to investigate the dynamic changes of endogenous phytohormones and carbohydrates content in root explants at different time points (0, 2, 4, 7, 14, 21, 28, and 60 days) during spontaneous centaury morphogenesis in vitro. Detailed analysis of cytokinins (CKs) showed that trans-zeatin (tZ) was the major bioactive CK at all time points. The corresponding riboside, tZ9R, was also determined in the majority of the identified transport forms, at all time-points. Further analysis of endogenous auxin revealed a significant increase in endogenous indole-3-acetic acid (IAA) after 21 days, when a huge jump in the ratio of IAA/bioactive CKs was also observed. The maximum total soluble sugar content was measured after 14 days, while a significant decrease was determined after 21 days, when the first regenerated adventitious shoots appeared. This undoubtedly indicates an increased energy requirement prior to the actual regeneration of the shoots. The obtained results indicate that the period from day 14 to day 21 involves the most dramatic disturbances in endogenous bioactive CKs, IAA and carbohydrate balance, which are very important and valuable factors for the onset of shoot regeneration.

Temporary Immersion System for Biomass Production of Salvia spp.: A Mini-Review

Salvia is a very valuable medicinal plant for the pharmaceutical industry. Tissue culture techniques can be used to increase the number of plants in a shorter time. Although protocols for in vitro propagation of more than 15 plant species have been developed, they are not yet efficient enough to increase mass propagation of plants. Therefore, the use of temporary immersion systems is necessary to increase the morphological quality of plants as well as their biomass in several Salvia species. In this chapter, progress in in vitro propagation in several Salvia species using liquid medium and automation is described.

Woodfordia fruticosa (L.) Kurz: in vitro biotechnological interventions and perspectives

Woodfordia fruticosa (L.) Kurz is a woody medicinal shrub (Lythraceae) commonly known as the "fire flame bush." W. fruticosa plant parts either alone or whole plant have a long history of recommended use in the Indian medicine systems of Ayurveda, Unani, and Siddha (AUS). This plant is prominently known for its pharmacological properties, viz., antimicrobial, anti-inflammatory, anti-peptic ulcer, hepatoprotective, immunomodulatory, antitumor, cardioprotective, analgesic, and wound healing activities. Its important phyto-constituents, woodfordin C, woodfordin I, oenothein B, and isoschimacoalin-A, exhibit in vitro or in vivo physiological activities beneficial to human health. As the plant is a rich storehouse of phyto-constituents, it is indiscriminately used in its wild habitats. Moreover, due to very poor seed viability and difficult-to-root qualities, it is placed under IUCN list of endangered plant species. For W. fruticosa, biomass production or to its conservation by in vitro regeneration is the best feasible alternative. Till date, only few important in vitro regeneration methods are reported in W. fruticosa. ISSR molecular markers based clonal fidelity and Agrobacterium-mediated transformation has been demonstrated, indicating that W. fruticosa is amenable to genetic manipulation and genome editing studies. This review presents concise summary of updated reports on W. fruticosa phyto-constituents and their biological activities, while a critical appraisal of biotechnological interventions, shortcomings, and factors influencing such potential areas success was presented. The unexplored gaps addressed here are relevant for W. fruticosa scientific innovations yet to come. In this paper, for the first time, we have presented a simple and reproducible protocol for synthetic seed production in W. fruticosa. KEY POINTS: • Critical and updated records on W. fruticosa phytochemistry and its activities • In vitro propagation and elicitation of secondary metabolites in W. fruticosa • Key bottlenecks, in vitro flowering, value addition, and outlook in W. fruticosa.

The Impact of Gold Nanoparticles on Somatic Embryogenesis Using the Example of Arabidopsis thaliana

Although the influence of nanoparticles (NPs) on developmental processes is better understood, little is known about their impact on somatic embryogenesis (SE). This process involves changes in the direction of cell differentiation. Thus, studying the effect of NPs on SE is essential to reveal their impact on cell fate. This study aimed to examine the influence of gold nanoparticles (Au NPs) with different surface charges on the SE of 35S:BBM Arabidopsis thaliana, with particular emphasis on the spatiotemporal localization of pectic arabinogalactan proteins (AGPs) and extensin epitopes in cells changing the direction of their differentiation. The results show that under the influence of nanoparticles, the explant cells of 35S:BBM Arabidopsis thaliana seedling origin did not enter the path of SE. Bulges and the formation of organ-like structures were observed in these explants, in contrast to the control, where somatic embryos developed. Additionally, spatiotemporal changes in the chemical composition of the cell walls during the culture were observed. Under the influence of Au NPs, the following effects were observed: (1) explant cells did not enter the SE pathway, (2) the impacts of Au NPs with different surface charges on the explants were variable, and (3) the compositions of the analyzed pectic AGPs and extensin epitopes were diverse in the cells with different developmental programs: SE (control) and non-SE (treated with Au NPs).

Phytochemical Composition and Biological Activities of Extracts from Early, Mature, and Germinated Somatic Embryos of Cotyledon orbiculata L

Cotyledon orbiculata L. (Crassulaceae)-round-leafed navelwort-is used worldwide as a potted ornamental plant, and it is also used in South African traditional medicine. The current work aims to assess the influence of plant growth regulators (PGR) on somatic embryogenesis (SE) in C. orbiculata; compare the metabolite profile in early, mature, and germinated somatic embryos (SoEs) by utilizing ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS); and determine the antioxidant and enzyme inhibitory potentials of SoEs. A maximum SoE induction rate of 97.2% and a mean number of SoEs per C. orbiculata leaf explant of 35.8 were achieved on Murashige and Skoog (MS) medium with 25 µM 2,4-Dichlorophenoxyacetic acid and 2.2 µM 1-phenyl-3-(1,2,3,-thiadiazol-5-yl)urea. The globular SoEs were found to mature and germinate best on MS medium with gibberellic acid (4 µM). The germinated SoE extract had the highest amounts of both total phenolics (32.90 mg gallic acid equivalent/g extract) and flavonoids (1.45 mg rutin equivalent/g extract). Phytochemical evaluation of SoE extracts by UHPLC-MS/MS reveals the presence of three new compounds in mature and germinated SoEs. Among the SoE extracts tested, germinated SoE extract exhibited the most potent antioxidant activity, followed by early and mature somatic embryos. The mature SoE extract showed the best acetylcholinesterase inhibitory activity. The SE protocol established for C. orbiculata can be used for the production of biologically active compounds, mass multiplication, and conservation of this important species.

Role of Sodium Nitroprusside on Potential Mitigation of Salt Stress in Centaury (Centaurium erythraea Rafn) Shoots Grown In Vitro

Soil salinity is one of the most common abiotic stressors that affects plant growth and development. The aim of this work was to investigate the influence of sodium nitroprusside (SNP), a donor of nitric oxide (NO), on the physiological response of common centaury (Centaurium erythraea) shoots grown under stress conditions caused by sodium chloride (NaCl) in vitro. Centaury shoots were first grown on nutrient medium containing different SNP concentrations (50, 100 and 250 μM) during the pretreatment phase. After three weeks, the shoots were transferred to nutrient media supplemented with NaCl (150 mM) and/or SNP (50, 100 or 250 μM) for one week. The results showed that salinity decreased photosynthetic pigments, total phenolic content and DPPH (1,1-diphenyl-2-picrylhydrazyl radical) concentration. The activities of antioxidant enzymes, namely superoxide dismutase (SOD), catalase (CAT) and peroxidase (POX), were also reduced under salt stress. However, MDA concentration was decreased, while H₂O₂ and proline content did not drastically change under the stress conditions caused by NaCl. Exogenous application of SNP altered the biochemical parameters of centaury shoots grown under salt stress. In this case, increased photosynthetic pigment content, total phenolics and proline content were noted, with reduced MDA, but not H₂O₂, concentration was observed. In addition, the exogenous application of SNP increased the degree of DPPH reduction as well as SOD, CAT and POX activities.

From synthesis to the biological effect of isoprenoid 2'-deoxyriboside and 2',3'-dideoxyriboside cytokinin analogues

Isoprenoid cytokinins are a class of naturally occurring plant signaling molecules. A series of prepared compounds derived from isoprenoid cytokinins (isopentenyladenine, trans-zeatin and cis-zeatin) with attached 2'-deoxy-d-ribose or 2',3'-dideoxy-d-ribose at the N⁹ position of the purine were prepared and their biological activities were examined. Different synthetic approaches were employed. The final compounds were characterized with variety of physicochemical methods (TLC, HPLC-MS, and NMR) and their cytokinin activity was determined in classical bioassays such as Amaranthus, tobacco callus, detached wheat leaf senescence and Arabidopsis thaliana root elongation inhibition assay. In addition, compounds were screened for activation of the cytokinin signaling pathway (bacterial receptor, competitive ligand binding and ARR5::GUS assay) to provide a detailed assessment of CK structure-activity relationship. The prepared compounds were found to be non-toxic to human cells and the majority of assays exhibited the highest activity of free bases while 2',3'-dideoxyribosides had very weak or no activity. In contrast to the free bases, all 2'-deoxyriboside derivatives were not toxic to tobacco callus even at the highest tested concentration (10^-4 moL/l) and compound 1 (iPdR) induced betacyanin synthesis at higher concentration even stronger than iP free base in the Amaranthus bioassay. The general cytokinin activity pattern base > riboside >2'-deoxyriboside > 2',3'-dideoxyriboside was distinguished.

Tissue Culture in Ornamentals: Cultivation Factors, Propagation Techniques, and Its Application

Ornamentals come in a variety of shapes, sizes, and colors to suit a wide range of climates, landscapes, and gardening needs. Compared to demand, a shortage of plant materials and diversity force the search for solutions for their constant acquisition and improvement to increase their commercial value, respectively. In vitro cultures are a suitable solution to meet expectations using callus culture, somatic embryogenesis, protoplast culture, and the organogenesis of protocorm-like bodies; many of these techniques are commercially practiced. Factors such as culture media, explants, carbohydrates, plant growth regulators, and light are associated with the success of in vitro propagation. Techniques, especially embryo rescue and somatic hybridization, are widely used to improve ornamentals. The development of synthetic seed allows season-independent seed production and preservation in the long term. Despite the advantages of propagation and the improvement of ornamentals, many barriers still need to be resolved. In contrast to propagation and crop developmental studies, there is also a high scope for molecular studies, especially epigenetic changes caused by plant tissue culture of ornamentals. In this review, we have accumulated and discussed an overall update on cultivation factors, propagation techniques in ornamental plant tissue culture, in vitro plant improvement techniques, and future perspectives.

New Insights Into Tissue Culture Plant-Regeneration Mechanisms

Plant regeneration occurs when plants repair or replace damaged structures based on the totipotency and pluripotency of their cells. Tissue culture is one of the most widely used regenerative technologies. Recently, a series of breakthroughs were made in the study of plant regeneration. This review summarizes two regenerative pathways in tissue culture: somatic embryogenesis and de novo organogenesis. Furthermore, we review the environmental factors influencing plant regeneration from explant sources, basal culture medium, plant growth regulators, and light/dark treatment. Additionally, we analyse the molecular mechanisms underlying two pathways. This knowledge will promote an understanding of the fundamental principles of plant regeneration from precursor cells and lay a solid foundation for applying plant micropropagation and genetic modification.

In Vitro Stress-Mediated Somatic Embryogenesis in Plants

Somatic embryogenesis (SE) serves as a key biological model for studying cell totipotency and the ontogenic processes of zygotic embryogenesis in plants. The SE process, under in vitro conditions, can be induced from different sources of explant cultivated in a culture medium with plant growth regulators (PGR) or by subjecting tissues to abiotic stress treatments. Somatic embryogenesis, in plant tissue culture (PTC), is a multifactorial event. The use of PGR, particularly auxins, is an important factor during induction. However, in vitro abiotic stress treatments are physiologically, biochemically, and genetically relevant and should be further studied.

Comparative transcriptomic and metabolic profiling provides insight into the mechanism by which the autophagy inhibitor 3-MA enhances salt stress sensitivity in wheat seedlings

BACKGROUND

Salt stress hinders plant growth and production around the world. Autophagy induced by salt stress helps plants improve their adaptability to salt stress. However, the underlying mechanism behind this adaptability remains unclear. To obtain deeper insight into this phenomenon, combined metabolomics and transcriptomics analyses were used to explore the coexpression of differentially expressed-metabolite (DEM) and gene (DEG) between control and salt-stressed wheat roots and leaves in the presence or absence of the added autophagy inhibitor 3-methyladenine (3-MA).

RESULTS

The results indicated that 3-MA addition inhibited autophagy, increased ROS accumulation, damaged photosynthesis apparatus and impaired the tolerance of wheat seedlings to NaCl stress. A total of 14,759 DEGs and 554 DEMs in roots and leaves of wheat seedlings were induced by salt stress. DEGs were predominantly enriched in cellular amino acid catabolic process, response to external biotic stimulus, regulation of the response to salt stress, reactive oxygen species (ROS) biosynthetic process, regulation of response to osmotic stress, ect. The DEMs were mostly associated with amino acid metabolism, carbohydrate metabolism, phenylalanine metabolism, carbapenem biosynthesis, and pantothenate and CoA biosynthesis. Further analysis identified some critical genes (gene involved in the oxidative stress response, gene encoding transcription factor (TF) and gene involved in the synthesis of metabolite such as alanine, asparagine, aspartate, glutamate, glutamine, 4-aminobutyric acid, abscisic acid, jasmonic acid, ect.) that potentially participated in a complex regulatory network in the wheat response to NaCl stress. The expression of the upregulated DEGs and DEMs were higher, and the expression of the down-regulated DEGs and DEMs was lower in 3-MA-treated plants under NaCl treatment.

CONCLUSION

3-MA enhanced the salt stress sensitivity of wheat seedlings by inhibiting the activity of the roots and leaves, inhibiting autophagy in the roots and leaves, increasing the content of both H₂O₂ and O₂•-, damaged photosynthesis apparatus and changing the transcriptome and metabolome of salt-stressed wheat seedlings.

The Arabinogalactan Protein Family of Centaurium erythraea Rafn

Centaurium erythraea (centaury) is a medicinal plant with exceptional developmental plasticity in vitro and vigorous, often spontaneous, regeneration via shoot organogenesis and somatic embryogenesis, during which arabinogalactan proteins (AGPs) play an important role. AGPs are highly glycosylated proteins belonging to the super family of O-glycosylated plant cell surface hydroxyproline-rich glycoproteins (HRGPs). HRGPs/AGPs are intrinsically disordered and not well conserved, making their homology-based mining ineffective. We have applied a recently developed pipeline for HRGP/AGP mining, ragp, which is based on machine learning prediction of proline hydroxylation, to identify HRGP sequences in centaury transcriptome and to classify them into motif and amino acid bias (MAAB) classes. AGP sequences with low AG glycomotif representation were also identified. Six members of each of the three AGP subclasses, fasciclin-like AGPs, receptor kinase-like AGPs and AG peptides, were selected for phylogenetic and expression analyses. The expression of these 18 genes was recorded over 48 h following leaf mechanical wounding, as well as in 16 tissue samples representing plants from nature, plants cultivated in vitro, and developmental stages during shoot organogenesis and somatic embryogenesis. None of the selected genes were upregulated during both wounding recovery and regeneration. Possible functions of AGPs with the most interesting expression profiles are discussed.

Determination of amino acids of some plants from Gentianaceae family

Medicines from plants are widely used in the complex treatment of different diseases every day. Therefore, theoretical and practical interest is the in-depth study of the herb of perspective plants like Centaurium erythraea Rafn. and Gentiana cruciata L. These plants have a long history of usage and interest of people. The aim of the study was to determine the content of amino acids in these plants. The amino acids composition and content in the herb of study species of the family Gentianaceae determined by the HPLC method. The results of the research revealed that the raw material of Centaurium erythraea Rafn. and Gentiana cruciata L. contains free and bound amino acids. Sixteen free and seventeen bound amino acids were identified in the herb of Centaurium erythraea Rafn. The herb of Gentiana cruciata L. contained thirteen free and fifteen bound amino acids. L-glutamic acid, L-arginine, L-aspartic acid, and L-cystine were predominant of Centaurium erythraea Rafn. herb. Amino acids L-lysine, L-serine, L-aspartic acid, and L-phenylalanine were present in the herb of Gentiana cruciata L. in the greatest amount. The metabolic processes in which these amino acids are involved connected to the medicinal properties of the study plants according to their use in official or nontraditional medicine.

Secondary Somatic Embryogenesis in Centaurium erythraea Rafn

Somatic embryogenesis (SE) is a developmental process during which plant somatic cells, under suitable conditions, produce embryogenic cells that develop into somatic embryos (se). SE is the most important method for plant propagation in vitro, having both fundamental and applicative significance. SE can be induced from different tissues and organs, but when se are used as explants, the process is recognized as secondary or cyclic SE. We induced secondary SE in Centaurium erythraea by application of 2,4-dichlorophenoxyacetic acid (2,4-D) and N-(2-chloro-4-pyridyl)-N′-phenylurea (CPPU). A medium containing 0.1 mgL⁻¹ 2,4-D and 0.25 mgL⁻¹ CPPU was optimal in terms of the number of primary SE explants forming se, the number of well-developed se per explant, and morphological appearance of the obtained se. These concentrations allowed SE to progress through three cycles, whereas at higher concentrations of 0.2 mgL⁻¹ 2,4-D and 0.5 mgL⁻¹ CPPU, only two cycles were achieved. Histological analysis revealed that secondary se are formed both directly and indirectly. Secondary SE readily germinated and converted into plantlets. Induction of cyclic SE contributes to the conservation efforts of this endangered medicinal plant and expands the spectrum of in vitro developmental pathways described in centaury—an emerging model in developmental biology.