Effects of light intensity and plant growth regulators on callus proliferation and shoot regeneration in the ornamental succulent Haworthia

Micropropagation and Genetic Fidelity of Fegra Fig (Ficus palmata Forssk.) and Grafting Compatibility of the Regenerated Plants with Ficus carica

Ficus palmata is an important fig species that produces edible and nutritious fruit and possesses several therapeutic uses. This study reports an effective method for the micropropagation of F. palmata using nodal explants. In vitro shoots were cultured for 7 weeks onto MS medium fortified with different concentrations of cytokinins, light intensities, sucrose concentrations, and light/dark incubation treatments. Optimal axillary shoot proliferation (10.9 shoots per explant) was obtained on a medium containing 30 g/L sucrose and supplemented with 2 mg/L 6-benzylaminopurine (BAP) under 35 μmol/m2/s light intensity. Dark incubation limited the foliage growth but favored shoot elongation and rooting compared with light incubation. Elongated shoots, under dark conditions, were rooted (100%; 6.67 roots per explant) onto MS medium containing 1 mg/L indole-3-acetic acid (IAA) and 1.5 g/L activated charcoal. The micropropagated plantlets were acclimatized with a 95% survival rate. In this study, the genetic fidelity of micropropagated F. palmata clones along with their mother plant was tested using randomly amplified polymorphic DNA (RAPD), inter-simple sequence repeats (ISSR), and start codon targeted (SCoT) molecular markers. The genetic similarity between the micropropagated plantlets and the mother plant of F. palmata was nearly 95.9%, assuring high uniformity and true-to-type regenerated plants. Using micropropagated F. palmata plantlets as a rootstock proved appropriate for the grafting F. carica 'Brown Turkey'. These findings contribute to the commercial propagation and production of the fig crop.

Tissue succulence in plants: Carrying water for climate change

Tissue succulence in plants involves the storage of water in one or more organs or tissues to assist in maintaining water potentials on daily or seasonal time scales. This drought-avoidance or drought-resistance strategy allows plants to occupy diverse environments including arid regions, regions with rocky soils, epiphytic habitats, and saline soils. Climate-resilient strategies are of increasing interest in the context of the global climate crisis, which is leading to hotter and drier conditions in many regions throughout the globe. Here, we describe a short history of succulent plants, the basic concepts of tissue succulence, the anatomical diversity of succulent morphologies and associated adaptive traits, the evolutionary, phylogenetic, and biogeographical diversity of succulent plants, extinction risks to succulents due to poaching from their natural environments, and the myriad uses and applications of economically important succulent species and the products derived from them. Lastly, we discuss current prospects for engineering tissue succulence to improve salinity and drought tolerance in crops.

Production of, Factors Affecting, Gene Regulations, and Challenges in Tissue Cultured Plant through Soilless Culture

Soilless culture also known as water based culture and substrate based culture has immense potential to grow tissue cultured plants in a closed and controlled environment system. This review analyzes the various factors that affect the vegetative growth, reproductive growth, metabolic processes, and gene regulatory functions of tissue cultured plants and the suitability of soilless culture for tissue culture plants. Experiments show that morphological and reproductive abnormalities are mitigated in tissue cultured plants by gene regulation in a closed and controlled environment system. Various factors of a soilless culture influence gene regulation and enhance cellular, molecular, and biochemical processes and compensate constraints in tissue cultured plants in closed and controlled environment conditions. The soilless culture can be utilized to harden and grow tissue culture plants. The tissue cultured plants counter water logging problems and are supplied with nutrients at 7 day intervals in the water based culture. It is necessary to analyze the involvement of regulatory genes in detail in combating challenges of tissue cultured plants in soilless cultures under closed systems. Detailed studies are also required to determine anatomy, genesis, and function of microtuber cells in tissue cultured plants.

Auxin and cytokinin synergism in micropropagation for mass production of Aloe vera

Aloe vera [Aloe vera (L.) Burm. f.] is considered a valuable medicinal plant worldwide due to its remarkable beneficial effects on human health. However, challenges in A. vera propagation hinder meeting the increasing demand in the health and beauty sectors. As an alternative method, in vitro propagation is crucial for the mass production of Aloe plants, which is a rapid method as well. Therefore, the present study aimed to establish an efficient micropropagation protocol for A. vera by in vitro optimization of the effect of different plant growth regulators (PGRs). For shoot proliferation, sterilized explants were inoculated on the Murashige and Skoog (MS) medium supplemented with 6-benzylaminopurine (BAP) and thidiazuron (0.5, 1.0, 2.0, and 4.0 mg/l) in combination with 0.5 mg/l naphthaleneacetic acid (NAA). Subsequently, indole-3-butyric acid (IBA) (1.0, 2.0, and 3.0 mg/l) was used for root induction. It was found that the explants cultured on the MS medium supplemented with 4.0 mg/l BAP + 0.5 mg/l NAA showed the highest percentage of response (90 ± 1.29) for shoot induction within the minimum number of days (5 ± 0.33). The highest number of shoots (2.7 ± 0.36) and length of shoots (4.7 ± 0.42 cm) per explant were also observed with the same concentration of PGRs. However, the highest number of roots (3.2 ± 0.57), length of roots (5.67 ± 0.21 cm), and root induction (80 ± 1.97 %) were noticed within the minimum number of days (11 ± 0.79) on the MS medium supplemented with 1.0 mg/l IBA. Thus, the proposed method is a quick and effective approach for the mass propagation of A. vera with appropriate dosages of auxins and cytokinins, which may allow meeting the increasing commercial demand.

HY5 inhibits in vitro shoot stem cell niches initiation via directly repressing pluripotency and cytokinin pathways

The efficiency of plant regeneration from explants is influenced by phytohormones and environmental conditions. Light has a particularly marked effect on in vitro shoot regeneration, and some light signaling factors are involved in shoot regeneration, while the underlying molecular mechanism remains elusive. Here, ELONGATED HYPOCOTYL5 (HY5), as the key transcription factor of light signaling, was found to inhibit shoot regeneration under a range of light conditions. The heightened shoot regeneration capacity of the hy5-215 mutant was less marked in the dark than in the light, showing that HY5-mediated inhibition of shoot regeneration is partly light dependent. The co-localization of WUSCHEL (WUS) and CLAVATA3 (CLV3) expressions was found to coincide with the initiation of stem cell niches in root explants during shoot regeneration. HY5 could directly repress CLV3 and WUS expression by binding to their respective promoters. In parallel, HY5 indirectly repressed CLV3 and WUS by binding to the ARABIDOPSIS RESPONSE REGULATOR12 (ARR12) promoter. The resulting dual regulation exerted by HY5 on WUS and CLV3 impeded the initiation of shoot stem cell niches. A HY5-mediated inhibitory pathway was identified that links cytokinin signaling and the pluripotency pathway during shoot regeneration.

Natural Surfactant Saponin from Tissue of Litsea glutinosa and Its Alternative Sustainable Production

In this research, we assessed the detergency properties along with chemical characteristic of the surfactant extracts from the most frequently cited detergent plants in Northern Thailand, namely, Sapindus rarak, Acacia concinna, and Litsea glutinosa. Moreover, as to provide the sustainable option for production of such valuable ingredients, plant tissue culture (PTC) as alternative method for industrial metabolite cultivation was also proposed herein. The results illustrated that detergent plant extracts showed moderate in foaming and detergency abilities compared with those of synthetic surfactant. The phytochemical analysis illustrated the positive detection of saponins in L. glutinosa plant extracts. The highest callus formation was found in L. glutinosa explant cultured with MS medium supplemented with 2.0 mg/L Indole-3-acetic acid (IAA). The callus extract was chemical elucidated using chromatography, which illustrated the presence of saponin similar to those from the crude leaf and Quillaja saponin extracts. Compact mass spectrometry confirmed that the surfactant was of the steroidal diagnostic type.

The Establishment of an Efficient Callus Induction System for Lotus (Nelumbo nucifera)

The lotus (Nelumbo nucifera) is one of the most popular aquatic plants in Asia, and has emerged as a novel model for studying flower and rhizome development, and primary and secondary metabolite accumulation. Here, we developed a highly efficient callus induction system for the lotus by optimizing a series of key factors that affect callus formation. The highest efficient callus production was induced on immature cotyledon and embryo explants grown on Murashige and Skoog (MS) basal medium containing an optimized combination of 3 mg/L 2,4-dichlorophenoxyacetic acid (2,4-D) and 0.5 mg/L 6-benzylaminopurine (6-BA). In addition, lotus callus induction was proven to be influenced by lotus genotypes, light conditions, the developmental stages of explants and the time of explant sampling. Collecting immature cotyledons from seeds of the genotype “Shilihe 1”, at 9 days post pollination, and to culture the explants in darkness, are proposed as the optimum conditions for lotus callus induction. Interestingly, highly efficient callus induction was also observed in explants of immature embryo derived aseptic seedlings; and a small amount of lotus benzylisoquinoline alkaloid (BIA) and obvious expression of BIA biosynthetic genes were detected in lotus callus.

Gene expression profiling reveals the effects of light on adventitious root formation in lotus seedlings (Nelumbo nucifera Gaertn.)

BACKGROUND

Lotus is an aquatic horticultural crop that is widely cultivated in most regions of China and is used as an important off-season vegetable. The principal root of lotus is degenerated, and adventitious roots (ARs) are irreplaceable for plant growth. We found that no ARs formed under darkness and that exposure to high-intensity light significantly promoted the development of root primordia. Four differential expression libraries based on three light intensities were constructed to monitor metabolic changes, especially in indole-3-acetic acid (IAA) and sugar metabolism.

RESULTS

AR formation was significantly affected by light, and high light intensity accelerated AR development. Metabolic changes during AR formation under different light intensities were evaluated using gene expression profiling by high-throughput tag-sequencing. More than 2.2 × 104 genes were obtained in each library; the expression level of most genes was between 0.01 and 100 (FPKF value). Libraries constructed from plants grown under darkness (D/CK), under 5000 lx (E/CK), and under 20,000 lx (F/CK) contained 1739, 1683, and 1462 upregulated genes and 1533, 995, and 834 downregulated genes, respectively, when compared to those in the initial state (CK). Additionally, we found that 1454 and 478 genes had altered expression in a comparison of libraries D/CK and F/CK. Gene transcription between libraries D/F ranged from a 5-fold decrease to a 5-fold increase. Twenty differentially expressed genes (DEGs) were involved in the signal transduction pathway, 28 DEGs were related to the IAA response, and 35 DEGs were involved in sugar metabolism. We observed that the IAA content was enhanced after seed germination, even in darkness; this was responsible for AR formation. We also observed that sucrose could eliminate the negative effect of 150 μMol IAA during AR development.

CONCLUSIONS

AR formation was regulated by IAA, even in the dark, where induction and developmental processes could also be completed. In addition, 36 genes displayed altered expression in carbohydrate metabolism and ucrose metabolism was involved in AR development (expressed stage) according to gene expression and content change characteristics.

The Effect of Light Intensity on the Expression of Leucoanthocyanidin Reductase in Grapevine Calluses and Analysis of Its Promoter Activity

To investigate the effect of light intensity on flavonoid biosynthesis, grapevine calluses were subjected to high light (HL, 250 μmol m⁻² s⁻¹) and dark (0 μmol m⁻² s⁻¹) in comparison to 125 μmol m⁻² s⁻¹ under controlled conditions (NL). The alteration of flavonoid profiles was determined and was integrated with RNA sequencing (RNA-seq)-based transcriptional changes of the flavonoid pathway genes. Results revealed that dark conditions inhibited flavonoid biosynthesis. Increasing light intensity affected flavonoids differently—the concentrations of flavonols and anthocyanins as well as the expressions of corresponding genes were less affected, whereas flavan-3-ol concentrations were predominantly increased, which caused enhanced trans-flavan-3-ol concentrations. Moreover, genes encoding leucoanthocyanidin reductase (LAR) exhibited different response patterns to light intensity changes—VviLAR1 expression increased with an increased light intensity, whereas VviLAR2 expression was insensitive. We further confirmed that the known transcription factors (TFs) involved in regulating flavan-3-ol biosynthesis utilized VviLAR1 as a target gene in grapevine calluses. In addition, VviLAR1 promoter activity was more sensitive to light intensity changes than that of VviLAR2 as determined using a transgenic Arabidopsis leaf system. These results suggested that light intensity had the most prominent effect on trans-flavan-3-ols in grapevine calluses and demonstrated that the two LAR genes had different response patterns to light intensity changes.

Cellular, Molecular, and Physiological Aspects of In Vitro Plant Regeneration

Plants generally have the highest regenerative ability because they show a high degree of developmental plasticity. Although the basic principles of plant regeneration date back many years, understanding the cellular, molecular, and physiological mechanisms based on these principles is currently in progress. In addition to the significant effects of some factors such as medium components, phytohormones, explant type, and light on the regeneration ability of an explant, recent reports evidence the involvement of molecular signals in organogenesis and embryogenesis responses to explant wounding, induced plant cell death, and phytohormones interaction. However, some cellular behaviors such as the occurrence of somaclonal variations and abnormalities during the in vitro plant regeneration process may be associated with adverse effects on the efficacy of plant regeneration. A review of past studies suggests that, in some cases, regeneration in plants involves the reprogramming of distinct somatic cells, while in others, it is induced by the activation of relatively undifferentiated cells in somatic tissues. However, this review covers the most important factors involved in the process of plant regeneration and discusses the mechanisms by which plants monitor this process.