Role of TDZ in the quick regeneration of multiple shoots from nodal explant of Vitex trifolia L.--an important medicinal plant

Development of efficient and scalable regeneration tissue culture method for Cannabis sativa

Large scale production of uniform disease-free plants is crucial for Cannabis sativa biotechnology. Existing micropropagation protocols rely heavily on shoot multiplication from existing meristems via direct organogenesis. Such protocols do not allow multiplication of plant material through continuous sub-culturing. Protocols that use indirect regeneration are usually not efficient enough and have very low multiplication rates. In the present study, an efficient protocol that uses a combination of direct organogenesis and callogenesis to induce multiple shoot development cultures is developed. Callogenesis was induced from various explants cultured on the media having various combinations of thidiazuron (TDZ) and naphthaleneacetic acid (NAA); best callogenesis and shoot regeneration was achieved from hypocotyl explants cultured on TDZ 0.4 mg l-1 NAA 0.2 mg l-1. Hypocotyls with cotyledonary node and shoot apical meristem were significantly better for shoot regeneration than explants without it. Shoots obtained from multiple shoot cultures were successfully rooted and then acclimatized under greenhouse conditions to develop into adult cannabis plants.

In vitro plant regeneration and Agrobacterium-mediated genetic transformation of a carnivorous plant, Nepenthes mirabilis

In nutrient-poor habitats, carnivorous plants have developed novel feeding strategies based on the capture and digestion of prey and the assimilation of prey-derived nutrients by specialized traps. The Nepenthes genus, comprising nearly 160 species, presents a remarkable pitcher-shaped trap, leading to great interest among biologists, but the species of this genus are listed as threatened. In this work, we developed a protocol for reproducing Nepenthes mirabilis through shoot regeneration from calli. The cultivation of stem segments of N. mirabilis on MS medium containing thidiazuron induced organogenic calli after 10 weeks. Subcultured calli exposed to 6-benzylaminopurine showed shoot regeneration in 3 weeks with considerable yields (143 shoots/g of calli). Excised shoots transferred to medium with indole-3-butyric acid allowed rooting in 4 weeks, and rooted plantlets had a 100% survival rate. Based on this method, we also developed an Agrobacterium-mediated genetic transformation protocol using calli as explants and ipt as a positive method of selection. Twelve weeks post infection, regenerated shoots were observed at the surface of calli. Their transgenic status was confirmed by PCR and RT-PCR. In conclusion, this study provides an efficient method for regenerating Nepenthes and the first protocol for its stable genetic transformation, a new tool for studying carnivory.

Micropropagation and Production of Health Promoting Lignans in Linum usitatissimum

Linum usitatissimum commonly known as flax or linseed is an important medicinal plant, produces medicinally potent lignans, used in the treatment of several human diseases. Lignans limited production in the natural plants does not meet the increasing market demand. This study was conducted to establish an easy and rapid method for the in vitro micropropagation and production of potent lignans and antioxidant secondary metabolites in linseed. The results indicated that hypocotyl explants under the effects of thidiazuron (TDZ: 0.5 mg/L) + kinetin (Kn: 0.5 mg/L) in the basal growth media, resulted in the optimal shoot organogenesis parameters (shoot induction frequency: 86.87%, number of shoots: 6.3 ± 0.36 and shoots length: 6.5 ± 0.54 cm), in 4 weeks. Further, TDZ supplementation in the culture media efficiently activated the antioxidant system in the in vitro raised shoots, wherein maximum production of total phenolic content, TPC (34.33 ± 0.20 mg of GAE/g DW); total flavonoid content, TFC (8.99 ± 0.02 mg of QE/g DW); DPPH free radical scavenging activity (92.7 ± 1.32%); phenylalanine ammonia-lyase activity, PAL (8.99 ± 0.02 U/g FW); and superoxide dismutase expression, SOD (3.62 ± 0.01 nM/min/mg FW) were observed in the shoot cultures raised in presence of TDZ: 0.5 mg/L + Kn: 0.5 mg/L. Nonetheless, considerable levels of pharmacologically active lignans such as secoisolariciresinol (SECO: 23.13-37.10 mg/g DW), secoisolariciresinol diglucoside (SDG: 3.32-3.86 mg/g DW) and anhydrosecoisolariciresinol diglucoside (ANHSECO: 5.15-7.94 mg/g DW) were accumulated in the regenerated shoots. This protocol can be scaled up for the commercial production of linseed to meet the market demands for lignans.

High frequency regeneration of plants via callus-mediated organogenesis from cotyledon and hypocotyl cultures in a multipurpose tropical tree (Neolamarkia Cadamba)

In this works, a simple, efficient and repeatable protocol was developed for in vitro regeneration via callus-mediated organogenesis of Neolamarkia Cadamba using cotyledonary petioles and hypocotyls. Effects of basal medium, plant growth regulators, the types and age of explant on the formation of adventitious buds/shoots were studied. Meanwhile, histological analysis for early ontogenic stages and genetic stability assessment by flow cytometry were investigated. Our investigation demonstrated that, compared with 6-benzyladenine (BA), N⁶-(2-isopentenyl) adenine (2-ip), Thidiazuron (TDZ) was the optimal cytokinin for buds/shoots induction on cotyledon and hypocotyl explants. Douglas-fir and sugar pine medium (DCR) supplemented with 22.7 μM TDZ and 0.27 μM α-naphthalene acetic acid (NAA) was most effective on bud induction, with the highest bud-induction rate and numbers of buds on cotyledon and hypocotyl explants. The available shoot per explant hit 35.2 when the induced callus sub-cultured to a medium without TDZ. It was found that TDZ could promote induction of the callus and the buds, however, continuous exposure beyond 4 weeks of supplemented high concentration (exceed 11.35 μM), TDZ was harmful to the proliferation and growth of buds/shoots. DCR appeared more efficiency than Murashige and Skoog medium (MS), Woody Plant medium (WPM), anther culture of cereal crops medium (N₆) on bud induction. Age of cotyledon and hypocotyl explants in 20-day to 25-day was most beneficial to adventitious buds/shoots formation. Histological investigation confirmed that the buds originated from the wounded incisions of cotyledonary petiole and hypocotyl fragments, with callus formation. The regeneration plantlets were successfully acclimatized in greenhouse, yielded above 95% survival rate in field, exhibited normal morphology and growth characteristics. The analysis of flow cytometry on N. cadamba indicated no variation in the ploidy levels between the regenerated plantlets and the donor trees. The developed procedure can be used for mass production, germplasm exchange and transgenic studies to improve the resistance of the species via Agrobacterium-mediated.

In vitro propagation of Securidaca longipedunculata (Fresen) from shoot tip: an endangered medicinal plant

BACKGROUND

Securidaca longipedunculata Fresen is an indigenous medicinal plant in Africa that has an important place in both traditional and modern medicine. This plant is endangered because of high seed dormancy, low germination rate, and over exploitation. Therefore, micropropagation method is important to address these problems. The objective of this study is to develop a micropropagation protocol for S. longipedunculata from shoot tip explants.

RESULTS

Among different Clorox concentrations, seeds sterilized with 10% Clorox for 10 min resulted in 85% decontamination and 80% germination. Among different media used to evaluate the rate of seed germination, seeds that were de-coated and transversally cut at the tip and cultured on basal MS medium resulted in 100% germination. The highest percentage of shoot initiation (87%) was obtained on MS medium containing 1.0 mg/l 6-Benzylaminopurine (BAP). The highest mean shoot number per explant (8.5 ± 0.69) was achieved on MS multiplication medium containing 1.5 mg/l BAP in combination with 0.1 mg/l Indole-3-butyric acid (IBA). The highest mean number of roots per explant (3.73 ± 0.69) was obtained on MS medium containing 2.0 mg/l Indole-3-acetic-acid (IAA). Among plantlets transferred to greenhouse, 60% survived after acclimatization.

CONCLUSIONS

This micropropagation protocol can be used for mass propagation of S. longipedunculata that contributes to its conservation and genetic improvement.

Thidiazuron-induced abnormalities in plant tissue cultures

Thidiazuron (TDZ) is a proven effective and potent synthetic plant growth regulator for organogenic, regeneration, and developmental pathways, including axillary and adventitious shoot proliferation, somatic embryogenesis, and in vitro flowering. TDZ has facilitated the establishment of in vitro cultures for several plant species, especially woody and recalcitrant plants, which has enabled their genetic transformation and improvement. Despite the effectiveness and advantages of using TDZ, several drawbacks are associated with its application in plant tissue culture. This review addresses the morphological, physiological, and cytogenetic abnormalities associated with the use of TDZ in vitro, and provides a summary of these abnormalities in several plant species.

Simple, rapid and efficient transformation of genotype Nisqually-1: a basic tool for the first sequenced model tree

Genotype Nisqually-1 is the first model woody plant with an available well-annotated genome. Nevertheless, a simple and rapid transformation of Nisqually-1 remains to be established. Here, we developed a novel shoot regeneration method for Nisqually-1 using leaf petiole and stem segment explants. Numerous shoots formed in the incision of explants within two weeks. The optimized shoot regeneration medium (SRM) contained 0.03 mg l-1 6-benzylaminopurine, 0.02 mg l-1 indole-3-butyric acid and 0.0008 mg l-1 thidiazuron. Based on this, Agrobacterium-mediated genetic transformation of stem explants was examined using the vector pBI121 that contains the β-glucuronidase (GUS) as a reporter gene. Consequently, factors affecting transformation frequency of GUS-positive shoots were optimized as follows: Agrobacteria cell suspension with an OD600 of 0.4, 20 min infection time, 2 days of co-cultivation duration and the addition of 80 µM acetosyringone into Agrobacteria infective suspension and co-cultivation SRM. Using this optimized method, transgenic plantlets of Nisqually-1 - with an average transformation frequency of 26.7% - were obtained with 2 months. Southern blot and GUS activity staining confirmed the integration of the foreign GUS gene into Nisqually-1. This novel transformation system for Nisqually-1 was rapid, efficient, and simple to operate and will improve more genetic applications in this model tree.

Biotechnological advances in Vitex species, and future perspectives

Vitex is a large genus consisting of 230 species of trees and shrubs with multiple (ornamental, ethnobotanic and pharmacological) uses. Despite this, micropropagation has only been used to effectively propagate and preserve germplasm a limited number (six) of Vitex species (V. agnus-castus, V. doniana, V. glabrata, V. negundo, V. rotundifolia, V. trifolia). This review on Vitex provides details of published micropropagation protocols and perspectives on their application to germplasm preservation and in vitro conservation. Such details serve as a practically useful user manual for Vitex researchers. The importance of micropropagation and its application to synthetic seed production, in vitro flowering, production of secondary metabolites, and the use of molecular markers to detect somaclonal variation in vitro, are also highlighted.

Efficient micropropagation and assessment of genetic fidelity of Boerhaavia diffusa L- High trade medicinal plant

Boerhaavia diffusa L is a medicinal herb with immense pharmaceutical significance. The plant is used by many herbalist, Ayurvedic and pharmaceutical industries for production biopharmaceuticals. It is among the 46 medicinal plant species in high trade sourced mainly from wastelands and generally found in temperate regions of the world. However, the commercial bulk of this plant shows genetic variations which are the main constraint to use this plant as medicinal ingredient and to obtain high value products of pharmaceutical interest from this plant. In this study, we have regenerated the plant of Boerhaavia diffusa L through nodal explants and evaluated genetic fidelity of the micropropagated plants of Boerhaavia diffusa L with the help of random amplified polymorphic DNA (RAPD) markers. The results obtained using RAPD showed monomorphic banding pattern revealing genetic stability among the mother plant and in vitro regenerated plants of Boerhaavia diffusa L.

An efficient in vitro process for cyclic clonal production of shoots from adult tree of Cassia alata L. and evaluation of genetic stability using DNA-based markers

An efficient, cyclic, two-step protocol for clonal in vitro regeneration system of an antiallergenic plant, Cassia alata, has been successfully developed. Nodal explants from a 5-year-old tree were cultured on Murashige and Skoog (MS) medium supplemented with various concentrations (1.0, 2.5, 5.0, 7.5, and 10.0 μM) of thidiazuron (TDZ). TDZ (5.0 μM) was found to be optimal for the formation of maximum shoot induction. Shoot proliferation and elongation increased when the regenerated shoots were subcultured on hormone-free MS medium after 4 weeks of exposure to TDZ. Nodal explants from in vitro regenerated microshoots to developed shoots, thus making the process recurrent. In 6 months duration, owing to the recurring nature of the protocol, large number of shoots could be produced from a single nodal explant from an adult tree. Shoots rooted best on MS supplemented medium with 0.5 μM IBA. Regenerated plantlets were acclimatized and successfully transplanted to the garden soil, where they grew well without any morphological and genetic variations. To confirm the uniformity, the genetic fidelity of in vitro raised C. alata clones was also assessed by using random amplified polymorphic DNA (RAPD) and inter-simple sequence repeat (ISSR) markers. The present regeneration process not only favored the clonal multiplication but also expressed the regeneration capability of in vitro regenerated microshoots and can be subjugated for catering enough raw materials to various pharma industries by continuous cyclic shoot production.