Improvement of somatic embryogenesis and plantlet conversion in Oplopanax elatus, an endangered medicinal woody plant

Plant regeneration from leaf mesophyll derived protoplasts of cassava (Manihot esculenta Crantz)

A high yield of isolated protoplast and reliable regeneration system are prerequisite for successful somatic hybridization and genome editing research. However, reproducible plant regeneration from protoplasts remains a bottleneck for many crops, including cassava. We evaluated several factors that influence isolation of viable protoplasts form leaf mesophyll, induction of embryogenic calli, and regeneration of plants in three cassava cultivars; Muchericheri, TMS60444 and Karibuni. A relatively higher protoplast yield was obtained with enzyme mixture containing 5 g/L Macerozyme and 10 g/L cellulase. Muchericheri recorded relatively higher protoplast yield of 20.50±0.50×106 whereas TMS60444 (10.25±0.25×106) had the least protoplast yield in 10 g/L cellulase and 4 g/L cellulase. Freshly isolated protoplast cells were plated on callus induction medium (CIM) solid medium containing MS basal salt, 60 g/L D-glucose, 30 g/L sucrose, B5 vitamins, 100 mg/L myo-inositol, 0.5 mg/L copper sulphate, 100 mg/L casein hydrolysate, 4.55 g/L mannitol, 0.1 g/L MES, 10 mg/L picloram and 3 g/L gelrite to induce protoplast growth and development. The three cultivars reached colony formation but no further development was observed in this culture method. Protoplast growth and development was further evaluated in suspension culture using varying cell densities (1, 2 and 3× 105 p/mL). Development with highest number of minicalli was observed in cell density of 3× 105 p/mL. Minicalli obtained were cultured on CIM supplemented with 10mg/L picloram. Callus induction was observed in all cell densities with the cultivars. Highest somatic embryogenesis was observed in 2× 105 p/ml while no somatic embryogenesis was observed in cell density of 1×105 p/mL. Somatic embryos were matured in EMM medium supplemented with 1 mg/L BAP, 0.02 mg/L NAA and 1.5 mg/L GA3 then germinated in hormone free medium for plant regeneration. This protocol which used simple mixture of commercial enzymes is highly reproducible and can be applied in biotechnology research on cassava.

Chemical profiling of root bark extract from Oplopanax elatus and its in vitro biotransformation by human intestinal microbiota

Oplopanax elatus (Nakai) Nakai, in the Araliaceae family, has been used in traditional Chinese medicine (TCM) to treat diseases as an adaptogen for thousands of years. This study established an ultra-performance liquid chromatography coupled with quadrupole time-of-flight tandem mass spectrometry (UPLC-Q-TOF/MS) method to identify chemical components and biotransformation metabolites of root bark extract from O. elatus. A total of 18 compounds were characterized in O. elatus extract, and 62 metabolites by human intestinal microbiota were detected. Two polyynes, falcarindiol and oplopandiol were recognized as the main components of O. elatus, whose metabolites are further illustrated. Several metabolic pathways were proposed to generate the detected metabolites, including methylation, hydrogenation, demethylation, dehydroxylation, and hydroxylation. These findings indicated that intestinal microbiota might play an essential role in mediating the bioactivity of O. elatus.

Efficient plant regeneration from embryogenic cell suspension cultures of Euonymus alatus

To establish an efficient plant regeneration system from cell suspension cultures of Euonymus alatus, embryogenic callus formation from immature embryos was investigated. The highest frequency of embryogenic callus formation reached 50% when the immature zygotic embryos were incubated on Murashige and Skoog (MS) medium supplemented with 1 mg/L 2,4-dichlorophenoxy acetic acid (2,4-D). At higher concentrations of 2,4-D (over 2 mg/L), the frequency of embryogenic callus formation declined significantly. The total number of somatic embryos development was highest with the 3% (w/v) sucrose treatment, which was found to be the optimal concentration for somatic embryo formation. Activated charcoal (AC) and 6-benzyladenine (BA) significantly increased the frequency of plantlet conversion from somatic embryos, but gibberellic acid (GA₃) had a negative effect on plantlet conversion and subsequent development from somatic embryos. Even though the cell suspension cultures were maintained for more than 1 year, cell aggregates from embryogenic cell suspension cultures were successfully converted into normal somatic embryos with two cotyledons. To our knowledge, this is the first successful report of a plant regeneration system of E. alatus via somatic embryogenesis. Thus, the embryogenic cell line and plant regeneration system established in this study can be applied to mass proliferation and production of pharmaceutical metabolite in E. alatus.

An innovative automated active compound screening system allows high-throughput optimization of somatic embryogenesis in Coffea arabica

Somatic embryogenesis (SE) faces many challenges in fulfilling the growing demand for elite materials. A high-throughput approach is required to accelerate the optimization of SE protocols by multiplying experimental conditions within a limited time period. For the first time in plant micropropagation, we have developed a miniaturized and automated screening system to meet high-throughput standards. Coffea arabica embryo regeneration, classically achieved in 250-ml Erlenmeyer flasks, was successfully miniaturized in 24-well plates, allowing a volume downscaling factor of 100 and a space saving of 53 cm²/well. Cell clusters were ground and filtered to fit the automated pipetting platform, leading to fast, reproducible and uniform cluster distribution (23.0 ± 5.5 cell clusters/well) and successful regeneration (6.5 ± 2.2 embryos/well). Pilot screening of active compounds on SE was carried out. Compounds belonging to the histone deacetylase inhibitor family were tested for embryo regeneration efficiency. Cells treated with 1 µM Trichostatin A showed a marked 3-fold increase in the number of regenerated embryos. When re-tested in 250-ml flasks, the same enhancement was obtained, thereby validating the miniaturized and automated screening method. These results showed that our screening system is reliable and well suited to screening hundreds of compounds, offering unprecedented perspectives in plant micropropagation.

Addition of ionophore A23187 increases the efficiency of Cocos nucifera somatic embryogenesis

The present study reports the effect of treatment of coconut embryogenic structure explants (derived from embryogenic callus) with the calcium ionophore A23187 (0, 1, 5, 10 µM) to promote somatic embryogenesis under in vitro conditions. The results showed no significant increase in the percentage of explants forming embryogenic callus, but with 1 µM ionophore there were significant increases in the formation of embryogenic structures per callus (2.8-fold), of somatic embryos per callus (1.5-fold) and also a greater absolute number (1.5-fold) of developing plantlets per callus. The ionophore treatment also promoted a change of pattern of the expression of the CnSERK gene during embryogenic callus formation. It is proposed that if the use of ionophore A23187 treatment is coupled with an embryogenic callus multiplication process there could be a potentially greater increase in the efficiency of the formation of somatic embryos and plantlets of coconut.

Evaluation of biochemical markers during somatic embryogenesis in Silybum marianum L

In present report effects of explants type, basal media and plant growth regulators (PGRs) were tested for induction of indirect somatic embryogenesis in medicinally important plant Silybum marianum L. Leaf, petiole and root explants were exploited in vitro on B5 (Gamborg), SH (Schenk and Hildebrandt) and MS (Murashige and Skoog) media for induction of embryogenic callus followed by somatic embryogenesis. Highest callus induction frequency (76 ± 4.8 %) was recorded when petiole explants of in vitro derived plantlets were cultured on B5 medium supplemented with 1.5 mg l⁻¹ 2,4-dichlorophenoxyacetic acid (2,4_D) in combination with 1.5 mg l⁻¹ Thidiazuron (TDZ). Induction and multiplication of somatic embryos were observed, when the embryogenic calluses were sub-cultured on to B5 medium containing 0.5 mg l⁻¹ 2,4-D plus 1.5 mg l⁻¹ TDZ. At this PGRs treatment, 77 % of the cultures responded with 39.1 somatic embryos per callus. Furthermore, MS0 medium was indicated more reponsive for growth and maturation of somatic embryos. Analysis of biochemical markers during various growth phases in somatic embryogenesis revealed that somatic embryos exhibited highest level of total carbohydrate, starch, ascorbic acid and total free amino acids. However, higher protein levels were detected in non-embryogenic callus. Nevertheless, considerable amount of silymarin (4.1 mg g⁻¹ DW) was detected in somatic embryos than other growth phases. Thus, the present study concluded that biochemical and physiological changes during embryogenesis are influenced by interplay of explants type, basal media and PGRs.