Activation of anthraquinone biosynthesis in long-cultured callus culture of Rubia cordifolia transformed with the rolA plant oncogene.

The RolA protein belongs to the RolB class of plant T-DNA oncogenes, and shares structural similarity with the papilloma virus E2 DNA-binding domain. It has potentially as an inducer of plant secondary metabolism, although its role in biotechnology has yet to be realised. In this investigation, a Rubia cordifolia callus culture transformed with the rolA plant oncogene for more than 10 years was analysed. Expression of the rolA gene in the callus line was stable during long-term cultivation, and growth parameters were both elevated and stable, exceeding those of the non-transformed control culture. The rolA-transformed calli not only demonstrated remarkably stable growth, but also the ability to increase the yield of anthraquinones (AQs) in long-term cultivation. After ten years of cultivating rolA callus lines, we observed an activation of AQ biosynthesis from 200 mg/l to 874 mg/l. The increase was mainly due to activation of ruberitrinic acid biosynthesis. The expression of key AQ biosynthesis genes was strongly activated in rolA-transgenic calli. We compared the effects of the rolA gene with those of the rolB gene, which was previously considered the most potent inducer of secondary metabolism, and showed that rolA was more productive under conditions of long-term cultivation.

Increase of anthraquinone content in Rubia cordifolia cells transformed by native and constitutively active forms of the AtCPK1 gene.

KEY MESSAGE: Overexpression of both native and mutant forms of AtCPK1 in Rubia cordifolia cells increased anthraquinone production and transcript abundance of the RcIPPI, RcOSBL, RcOSBS , and RcICS genes to different extents. Calcium-dependent protein kinases (CDPKs) are involved in various cell processes and are regulated by a calcium signal system. CDPKs also function in plant defense against stress factors such as pathogens, temperature, and salinity. In this study, we compared the effect of heterologous expression of two forms of the Arabidopsis AtCPK1 gene, native and constitutively active (Ca(2+)-independent), on anthraquinone production in transgenic Rubia cordifolia cells. Significant qualitative and quantitative differences were found in the content of anthraquinone derivatives in control and AtCPK1-transgenic calli. Expression of the AtCPK1 gene increased anthraquinone production by 3 and 12 times for native and constitutively active forms, respectively, compared with control cells. In addition, we identified and quantified the expression of genes encoding key enzymes of the anthraquinone biosynthesis pathway, including isochorismate synthase (ICS), o-succinylbenzoate synthase (OSBS), o-succinylbenzoate ligase (OSBL), and isopentenyl diphosphate isomerase (IPPi). In all AtCPK1-transgenic cell lines, expression of ICS, OSBS, OSBL, and IPPi increased considerably at 14-15 days of subculture and decreased at the end of cultivation (30 days). The results suggest that both native and constitutively active AtCPK1 forms induced anthraquinone accumulation at the logarithmic growth stage via enhancement of expression of genes involved in the metabolism of anthraquinones or their regulatory mechanisms.

Development of an encapsulation-vitrification protocol for Rubia akane (nakai) hairy roots: a comparison with non-encapsulation.

BACKGROUND: A comparison of different cryopreservation techniques should be based on the characteristics of both the methodology and the material in question using an optimized procedure. OBJECTIVE: This study aimed at developing an encapsulation-vitrification procedure for hairy roots of Rubia akane using alternative loading and vitrification solutions, based on the existing optimized droplet-vitrification procedure. MATERIALS AND METHODS: Encapsulated roots were first precultured in liquid medium with 10% sucrose for 3 days, then with 17.5 % sucrose for 1 day, after which they were osmoprotected with solution C6-40 % (20 % glycerol + 20 % sucrose) for 50 min, cryoprotected with solution A3-90 % (37.5 % glycerol + 15 % DMSO + 15 % EG + 22.5 % sucrose, w/v) on ice for 40 min, cooled and warmed in 2 ml cryovials, and unloaded in 35% sucrose solution for 60 min. RESULTS: Through the application of this procedure to aged-clustered roots, up to 97.5 % post-cryopreservation regeneration was observed. In our previous study, droplet-vitrification of hairy roots of R. akane resulted in 83.8 % post-rewarming regeneration following preculture with 10 % sucrose for 2 days and 17.5 % sucrose for 4-5 h, and osmoprotection with solution C4-35 % (17.5 % glycerol + 17.5 % sucrose) for 30 min, and cryoprotection with solution A3-70 % (29.2 % glycerol + 11.7 % DMSO + 11.7% EG + 17.4% sucrose, w/v) on ice for 20 min. In the present study, higher post-cryopreservation regeneration was observed by using a higher concentration of vitrification solution (A3-70 % → A3-90 %, B5-80 % → B1-100 %) and/or a longer cryoprotection duration (A3-70 % at room temperature (RT) for 8 min → 15-30 min, on ice for 20 min → 40-80 min; B5-80 % for 15 min → 30-60 min). CONCLUSION: Even though encapsulation provided some degree of protection from the cytotoxicity of vitrification solutions to cytotoxicity-sensitive R. akane hairy roots, an overall higher post-cryopreservation regrowth was obtained using the droplet-vitrification procedure under optimized conditions. This result implies that this sensitive material was not sufficiently cryoprotected, and thus, rapid cooling and warming using foil strips was more efficient than cryopreservation of encapsulated samples.

[Study on the HPLC-DAD fingerprint chromatograms of Radix Rubiae from different areas in China].

OBJECTIVE: To establish the HPLC-DAD fingerprint of Radix Rubiae and provide a quality control method for it. METHODS: The method HPLC-DAD was performed on a YMC C,18 (250 mm x 4.6 mm, 5 microm) column with gradient elution of acetonitrile-0.2% phosphoric acid solution as mobile phase, flow rate at 1.0 mL/min, detection wavelength at 280 mm, and the column temperature at 25 degrees C, and the analysis time was 60 min. RESULTS: The average similarity of the fnigerprint chromatograms was over 0.94 in 6 batches samples of different areas in China. CONCLUSION: This method can be applied for the determination of Radix Rubiae from different areas.

TNT removal from culture media by three commonly available wild plants growing in the Caribbean.

Plants growing in the Caribbean, Rubia tinctorum, Lippia dulcis and Spermacoce remota, were used in vitro to remove TNT from culture media. Plants were found to be resistant to high TNT levels. S. remota was able to remove TNT in less than 48 h. Part of the TNT was physically removed from the culture media by evaporation.

Role of reactive oxygen species and proline cycle in anthraquinone accumulation in Rubia tinctorum cell suspension cultures subjected to methyl jasmonate elicitation.

Elicitors are compounds or factors capable of triggering a defense response in plants. This kind of response involves signal transduction pathways, second messengers and events such as Reactive Oxygen Species (ROS) generation, proline accumulation and secondary metabolite production. Anthraquinone (AQs) biosynthesis in Rubia tinctorum L. involves different metabolic routes, including shikimate and 2-C-methyl-d-erythritol-4-phosphate (MEP) pathways. It has been proposed that the proline cycle could be coupled with the pentose phosphate pathway (PPP), since the NADP+ generated by this cycle could act as a cofactor of the first enzymes of the PPP. The end-product of this pathway is erithrose-4-phosphate, which becomes the substrate of the shikimate pathway. The aim of this work was to study the effect of methyl jasmonate (MeJ), a well-known endogenous elicitor, on the PPP, the proline cycle and AQs production in R. tinctorum cell suspension cultures, and to elucidate the role of ROS in MeJ elicitation. Treatment with MeJ resulted in AQs as well as proline accumulation, which was mimicked by the treatment with a H2O2-generating system. Both MeJ-induced effects were abolished in the presence of diphenyliodonium (DPI), a NADPH oxidase inhibitor (main source of ROS). Treatment with the elicitor failed to induce PPP; therefore, this route did not turn out to be limiting the carbon flux to the shikimate pathway.

Effect of shear stress on anthraquinones production by Rubia tinctorum suspension cultures.

Suspension cultures of Rubia tinctorum, an anthraquinones (AQs) producer, were grown both in Erlenmeyer flasks at 100 rpm and in a 1.5 L mechanically stirred tank bioreactor operating at 450 rpm. The effect of hydrodynamic stress on cell viability, biomass, and AQs production was evaluated. Cell viability showed a transient decrease in the bioreactor during the first days, returning to the initial values toward the end of the culture time. The biomass obtained in the bioreactor was 29% lower than that attained in the Erlenmeyer flasks. The H2O2 production in the bioreactor (with peaks at 7 and 10 days) was about 15 times higher than that obtained in the flasks. A clear relationship exists between the maximum concentration of H2O2 generated and AQs produced. The AQs content in the bioreactor was 233% higher than that in the Erlenmeyer flasks. The AQs specific productivity in the stirred tank and in the Erlenmeyer flasks was 70.7 and 28.5 micromol/g FW/day, respectively. This production capability was maintained in the regrowth assays. On the other hand, the negative effects of hydrodynamic stress on viability and biomass concentration observed in the bioreactor culture were reverted in the regrowth cultures. It can be concluded that R. tinctorum suspension cultures are able to grow in stirred tanks at 450 rpm responding to the hydrodynamic stress with higher concentrations of AQs, which suggest the possibility of a technological approach taking advantage of this phenomenon.

Effects of Ca(2+) channel blockers and protein kinase/phosphatase inhibitors on growth and anthraquinone production in Rubia cordifolia callus cultures transformed by the rolB and rolC genes.

The transformation of Rubia cordifolia L. cells by the 35S- rolB and 35S- rolC genes of Agrobacterium rhizogenes caused a growth inhibition of the resulting cultures and an induction of the biosynthesis of anthraquinone-type phytoalexins. Inhibitor studies revealed a striking difference between the rolC- and rolB-gene-transformed cultures in their sensitivity to verapamil, an L-type Ca(2+) channel blocker. The rolC culture possessed a 2-fold lowered resistance to the inhibitor than the normal culture, while the rolB culture was 4-fold more resistant to the treatment. Additionally, growth of the rolC culture was totally inhibited when the culture was grown in Ca(2+)-free medium, whereas growth of the rolB culture was reduced by less than half. We interpreted these results as evidence for a lack of calcium homeostasis in both transgenic cultures. Anthraquinone (AQ) production was not inhibited in the normal or transformed cultures by the Ca(2+) channel blockers verapamil and LaCl(3), or by diphenylene iodonium, an inhibitor of NADPH oxidase, or by the protein kinase inhibitor staurosporine. These results indicate that the induction of AQ production in non-transgenic and transgenic cultures does not proceed through the activation of the common Ca(2+)-dependent NADPH oxidase pathway that mediates signal transduction between an elicitor-receptor complex via transcriptional activation of defense genes. Okadaic acid and cantharidin, inhibitors of protein phosphatases 1 and 2A, caused an increase in AQ production in transgenic cultures. Okadaic acid stimulated AQ accumulation in the non-transformed culture, whereas cantharidin had no effect. These results show that different phosphatases are involved in AQ synthesis in normal and transgenic cultures of R. cordifolia.