Cytokinin-Based Tissue Cultures for Stable Medicinal Plant Production: Regeneration and Phytochemical Profiling of Salvia bulleyana Shoots

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.

Comparative study of the doses of cytokinin in the quality of caigua (Cyclanthera pedata L.) in Peru

Bioavailability of nutrients, the scarcity of synthetic fertilisers, and the rising cost of fuel have all contributed to an increase in production costs, which has in turn reduced crop productivity and led scientists to seek out new methods to ensure high-quality output. In this context, various cytokinins dosages were tested in Peru to see whether they affected the quality of caigua, in an effort to address these issues. To mitigate these problems, a pot experiment was carried out to check the effects of various doses of cytokinin in the quality of caigua in Peru. The experiment consisted of 5 treatments including (0, 50, 100, 150 and 200 mL of cytokinin) by using (Anthesis Plus per 200 L of water) as a source, each with three replicates and placed following a randomized complete block design (RCBD). Treatment with 100 mL of cytokinins foliar analysis resulted in a caigua length of 18.9 cm, an increase in diameter of 5.65 cm, and an improvement in pulp thickness of 7.60 millimeters. Physiological parameters of caigua plants taken after 45 days of sowing were considerably improved with the same treatment. Similarly, N, K and Zn concentration in leaf was higher in case of 100 mL of cytokinins foliar analysis. Therefore, policymakers must advise using the recommended quantity of cytokinins to bring about regime transition, and formers can gain by injecting 100 mL of cytokinins to boost production and the economy. It was concluded that the adequate dose of cytokinins is in treatment T3, which raised value of potassium concentration in leaves, this influenced optimal development, strengthening against environmental stress and therefore quality. For this reason, research was carried out on the comparative study of cytokinin doses in the quality of caigua in Peru; the objective was to determine the appropriate dose to obtain higher quality fruit. Likewise, it was underlined that the objective was to employ an ecological alternative of plant origin such as the usage of phytohormone that stimulates the growth of the plant and consequently the quality of the fruit. The obtained the results were served as a recommendation for farmers in the area.

Effect of Light Conditions on Polyphenol Production in Transformed Shoot Culture of Salvia bulleyana Diels

Various strategies have been used to increase the efficiency of secondary metabolite production in Salvia plants. This report is the first to examine the spontaneous development of Salvia bulleyana shoots transformed by Agrobacterium rhizogenes on hairy roots and the influence of light conditions on the phytochemical profile of this shoot culture. The transformed shoots were cultivated on solid MS medium with 0.1 mg/L of IAA (indole-3-acetic acid) and 1 mg/L of m-Top (meta-topolin), and their transgenic characteristic was confirmed by PCR-based detection of the rolB and rolC genes in the target plant genome. This study assessed the phytochemical, morphological, and physiological responses of the shoot culture under stimulation by light-emitting diodes (LEDs) with different wavelengths (white, WL; blue, B; red, RL; and red/blue, ML) and under fluorescent lamps (FL, control). Eleven polyphenols identified as phenolic acids and their derivatives were detected via ultrahigh-performance liquid chromatography with diode-array detection coupled to electrospray ionization tandem mass spectrometry (UPLC-DAD/ESI-MS) in the plant material, and their content was determined using high-performance liquid chromatography (HPLC). Rosmarinic acid was the predominant compound in the analyzed extracts. The mixed red and blue LEDs gave the highest levels of polyphenol and rosmarinic acid accumulation (respectively, 24.3 mg/g of DW and 20.0 mg/g of DW), reaching two times greater concentrations of polyphenols and three times greater rosmarinic acid levels compared to the aerial parts of two-year-old intact plants. Similar to WL, ML also stimulated regeneration ability and biomass accumulation effectively. However, the highest total photosynthetic pigment production (1.13 mg/g of DW for total chlorophyll and 0.231 mg/g of DW for carotenoids) was found in the shoots cultivated under RL followed by BL, while the culture exposed to BL was characterized as having the highest antioxidant enzyme activities.

Role of Phytohormones in Biomass and Polyphenol Accumulation in Salvia bulleyana In Vitro Culture

Salvia bulleyana is a plant native to the Chinese Yunnan Province. This species has been used in traditional Chinese medicine as a substitute for Danshen (the roots of Salvia miltiorrhiza). The aim of our study was to establish an effective system for propagating S. bulleyana shoots to obtain large amounts of material rich in bioactive compounds. Phytohormones were used to regulate shoot growth and regeneration potential and influence plant secondary metabolism. The shoot tips were incubated on a Murashige and Skoog agar medium supplemented with 0.1 or 0.5 mg/L IAA (indole-3-acetic acid) and the cytokinins benzylaminopurine (BAP), meta-topoline (M-T), 6-benzylaminopurine riboside (RBAP), N-benzyl-9-(2-tetrahydropyranyl)-adenine (BPA) or kinetin, (K) at concentrations of 0.5, 1 or 2 mg/L. It was observed that the type and concentration of growth regulator significantly influenced the regeneration potential of S. bulleyana shoots. The highest multiplication rate was obtained when 0.1 mg/L IAA and 2 mg/L BPA were used. Under these conditions, 100% of shoot tips formed buds and almost seven buds/shoot per explant were obtained after five weeks. Meanwhile, the highest biomass was found for shoots growing on a medium supplemented with 0.1 mg/L IAA and 1 mg/L M-T: 1.2 g of fresh weight and 0.17 g of dry weight. However, a medium with 0.1 mg/L IAA and 2 mg/L RBAP was most favorable for bioactive phenolic acid content, with a total polyphenol level (37.7 mg/g dw) 4.5 times higher than in shoots grown on medium without growth regulators (8.23 mg/g dw). Finally, optimal conditions were selected by TOPSIS (technique for order of preference by similarity to the ideal solution); the culture of S. bulleyana grown on an MS medium containing 0.1 mg/L IAA and 1 mg/L M-T was found to be the most efficient for polyphenol accumulation and can be used for the production of medicinally relevant compounds.

Agrobacterium-mediated genetic transformation of the most widely cultivated superior clone Eucalyptus urophylla × E. grandis DH32-29 in Southern China

Eucalyptus, as an economically important species for wood and paper industries, remains a challenge to genetic improvement by transgenic technology owing to the deficiency of a highly efficient and stable genetic transformation system, especially in cultivated superior clones. Eucalyptus urophylla × E. grandis clone DH32-29 is most widely planted in southern China, but it is relatively recalcitrant to adventitious bud regeneration, which blocks the establishment of a genetic transformation system. Here, an efficient adventitious bud regeneration and transformation system of Eucalyptus was established using E. urophylla × E. grandis DH32-29 as material. The in vitro leaves from microshoots that were subcultured for 20-25 days were immersed into liquid Woody Plant Medium supplemented with 0.02 mg·L^-1 α-naphthaleneacetic acid (NAA) and 0.24 mg·L^-1 forchlorfenuron [callus-inducing medium (CIM)]. After 15 days, explants were transferred to a medium containing 0.10 mg·L^-1 NAA and 0.50 mg·L^-1 6-benzyladenine (shoot-inducing medium, SIM) for adventitious bud induction. The highest regeneration efficiency of adventitious buds was 76.5%. Moreover, an Agrobacterium tumefaciens-mediated genetic transformation system was optimized. The leaves were precultured for 7 days and infected for 30 min with A. tumefaciens strain EHA105 grown to a bacterial density of 0.3 (OD₆₀₀). After 72 h of cocultivation in the dark, leaves were transferred to CIM supplemented with 100 mg·L^-1 cefotaxime (Cef), 100 mg·L^-1 timentin, and 15 mg·L^-1 kanamycin (Kan) for 15 days to induce calluses. Then, the explants were transferred to SIM supplemented with the same concentration of antibiotics, and the fresh medium was replaced every 15 days until resistant adventitious buds appeared. After inducing roots in root-inducing medium supplemented with 200 mg·L^-1 Cef and 75 mg·L^-1 Kan, completely transgenic plants were obtained. Using the aforementioned method, the transformation frequency can reach 1.9%. This provides a powerful approach for genetic improvement of E. urophylla × E. grandis DH32-29 and gene function analysis in Eucalyptus.

Somaclonal Variation-Advantage or Disadvantage in Micropropagation of the Medicinal Plants

Cell and tissue plant cultures are used either to save vulnerable species from extinction or to multiply valuable genotypes, or both, and are widely applied for economically important plant species. For medicinal plants, the use of in vitro technologies for the production of secondary metabolites and pathogen-free plants has been greatly developed. Two opposite aspects characterize the in vitro micropropagation of medicinal plants: maintaining genetic fidelity for the perpetuation and preservation of elites, and the identification and exploitation of somaclonal variations associated with new, useful traits. A balance between what is advantageous and what is undesirable is necessary, and this implies the identification of somaclonal variability at all levels, from the phenotypic to molecular ones. This review addresses the somaclonal variation arising from the in vitro multiplication of medicinal plants from three perspectives: cytogenetics, genetics, and epigenetics. The possible causes of the appearance of somaclones, the methods for their identification, and the extent to which they are desirable are presented comparatively for different plant species with therapeutic properties. The emphasis is on the subtle changes at the genetic and epigenetic level, as it results from the application of methods based on DNA markers.

The Effect of the Stress-Signalling Mediator Triacontanol on Biochemical and Physiological Modifications in Dracocephalum forrestii Culture

Triacontanol (TRIA) has been reported to influence signal transduction in the crosstalk triggered by various stress factors. As a signal player, it is also known to affect many physiological processes, including enhancing the biosynthesis of secondary metabolites. Such knowledge can be used to direct or boost the production of bioactive secondary compounds without stress induction. Therefore, the aim of this study is to evaluate the use of TRIA as a factor stimulating the growth and production of bioactive compounds in the shoot culture of Dracocephalum forrestii. TRIA was applied at three concentrations (2.5, 5, and 10 µM), alone or in combination with phytohormones (6-benzylaminopurine and indole-3-acetic acid). After five weeks, growth and physiochemical parameters (chlorophyll content, antioxidant enzyme activity, and phenolic acid level) were determined. The results indicate that TRIA application significantly increased shoot dry weight, chlorophyll content, antioxidant enzyme activities (superoxide dismutase, peroxidase, and catalase), and total polyphenol level; it also influenced the multiplication ratio in combination with growth regulators. The greatest antioxidant enzyme activity was observed for 5 µM TRIA in hormone-free medium, while the most significant secondary metabolite production was obtained for phytohormone-containing medium supplemented with 10 µM TRIA: total phenolic acid content (19.4 mg/g dry weight) was twice that of the control. Hence, the TRIA application appears to be a valuable biotechnology technique for modifying plant metabolite production.

Micropropagation of Seed-Derived Clonal Lines of the Endangered Agave marmorata Roezl and Their Compatibility with Endophytes

Simple Summary

The wild Agave marmorata Roezl has been classified as an endangered species. Extracting these plants from the forest for commercial purposes and long maturation periods of close to 30 years have contributed to their loss. A. marmorata interacts with pollinators and other Agaves species to maintain genetic variability. Thus, the conservation and restoration of the agave ecosystem is an ecological challenge. Typically, agave micropropagation use meristem or leaves as explants to rapidly produce uniform agave plants in age and size on a large scale leading to homogeneous plantations. However, introducing these clones to the field reduces genetic variability. This study evaluated in vitro micropropagation of A. marmorata from seeds to generate clonal lines. The selected seedlings exhibited variations in multiplication capacity and stable tissue formation. Variations in clonal lines could be exploited to produce high-quality plants with different capacities, such as faster propagation, enhanced stress adaptation, and continued growth under nutrient limitation conditions, consequently maintaining genetic variability. Furthermore, some clonal lines were inoculated with four endophytic bacteria to identify other differences among these plants, including endophyte-host compatibility. Variable responses to inoculation were observed among clonal lines. We found that Achromobacter xylosoxidans was compatible, unlike Enterobacter cloacae which caused plant death.

Abstract

A. marmorata is the raw material used for tepextate mescal production but is classified as an endangered species. In the present study, we obtain and multiply clonal lines of Agave marmorata Roezl by selecting seedlings derived from seeds. Ten seedlings from two lots of 400 germinated seeds were selected for axillary bud proliferation induced by BAP 5 mg/L in vitamin-free Murashige and Skoog’s medium. Differences in shoot numbers, heights and senescent tissue formation were observed. Notably, the AM32 line formed 84 shoots and presented low senescent tissue after 60 d of culture. We also selected the AM31 and AM33 clonal lines. Four-month shoots were extracted with 80% methanol in water to determine the total content of saponins, flavonoids, and phenolic acids and compare the three clonal lines. Some bioactive molecules were identified using HPLC techniques and MALDI-TOF mass spectrometry none showed significant differences in content. Additionally, plants derived from the clonal lines were inoculated with four endophytic bacteria. Among these, Achromobacter xylosoxidans supported plant growth of AM32. A notable effect of plant death was observed after inoculation with Enterobacter cloacae, an endophyte of A. tequilana. Additionally, Pseudomonas aeruginosa, an endophyte from A. marmorata, reduced biomass. Our results demonstrate the incompatibility of A. marmorata to E. cloacae and specialization between the host plant and its endophytes. The compatibility of the plant-endophyte could be exploited to boost the establishment and stability of mutualisms to benefit plant development, stress tolerance and pathogen resistance. The differences in multiplication capacity, stable tissue formation, and endophyte biotization responses may indicate genetic variability. Clonal selection and micropropagation from seed-derived plants could contribute to conserving the endangered A. marmorata plant for reforestation in their natural habitats, thus, assuring mass propagation for sustainable industrial production of mescal, bioactive compounds, and prebiotics.

Cytokinin biosynthesis in cyanobacteria: Insights for crop improvement

Cytokinins, a type of phytohormones that induce division of cytoplasm, have considerable value in agriculture due to their influences on several physiological processes of plants such as morphogenesis, development of chloroplast, seed dormancy, leaf senescence, etc. Previously, it was assumed that plants obtain cytokinin from the soil produced by microbes as these hormones were first discovered in soil-inhabiting bacteria i.e., Agrobacterium tumefaciens. Later, the cytokinin biosynthesis gene, i.e., ipt gene, has been reported in plants too. Though plants synthesize cytokinins, several studies have reported that the exogenous application of cytokinins has numerous beneficial effects including the acceleration of plant growth and boosting economic yield. Cyanobacteria may be employed in the soil not only as the source of cytokinins but also as the source of other plant growth-promoting metabolites. These organisms biosynthesize the cytokinins using the enzyme isopentenyl transferases (IPTs) in a fashion similar to the plants; however, there are few differences in the biosynthesis mechanism of cytokinins in cyanobacteria and plants. Cytokinins are important for the establishment of interaction between plants and cyanobacteria as evidenced by gene knockout experiments. These hormones are also helpful in alleviating the adverse effects of abiotic stresses on plant development. Cyanobacterial supplements in the field result in the induction of adventitious roots and shoots on petiolar as well as internodal segments. The leaf, root, and stem explants of certain plants exhibited successful regeneration when treated with cyanobacterial extract/cell suspension. These successful regeneration practices mark the way of cyanobacterial deployment in the field as a great move toward the goal of sustainable agriculture.