Hairy root cultures of butterfly pea (Clitoria ternatea L.): Agrobacterium × plant factors influencing transformation

Genetic transfection, hairy root induction and solasodine accumulation in elicited hairy root clone of Solanum erianthum D. Don

An efficient genetic transfection technique has been established using A4 strain of Agrobacterium rhizogenes for the first time in a medicinally valuable plant Solanum erianthum D. Don. The explants were randomly pricked with sterile needle, inoculated with bacterial suspension. The infected leaves were then washed and transferred to MS basal medium fortified with cefotaxime for hairy root induction. A maximum transformation efficiency of 72 % has been recorded after two days of co-cultivation period. The transfer of rolA and rolB genes from the bacterium to the plant genome has been confirmed in five transformed hairy rootlines by standard Polymerase Chain Reaction technique. On the basis of growth analysis and secondary metabolite study two potential rhizoclones (A4-HR-A and A4-HR-B) were selected. Rhizoclone A4-HR-A can produce highest amount of alkaloid, phenolic and flavonoid, whereas A4-HR-B was observed to be highest tannin producer. Alkaloid like solasodine, commercially important for steroidal drug synthesis, was quantified from leaf and A4-HR-A clone by an improved High Performance Liquid Chromatography method. This showed a sustainable increase (1.33 fold) in production of solasodine in hairy rootline.

Comparison of Profiling of Hairy Root of Two Tibetan Medicinal Plants Przewalskia tangutica Maxim. and Anisodus tanguticus Maxim

Background:

Tropane Alkaloids (TAs) are important drugs for curing many diseases in the medical industry.

Methods:

To sustainably exploit TA resources in endangered traditional Tibetan herbs, the hairy root (HR) systems of Przewalskia tangutica Maxim. and Anisodus tanguticus Maxim. were compared under the same culture conditions.

Results:

The results indicated that both the Agrobacterium rhizogenes strains and explants affected the HR induction frequency, MSU440, A4 and LBA9402 strains could induce hairy roots following infection of cotyledon and hypocotyl of A. tanguticus while LBA9402 could not induce HR on either explants of P. tangutica. The efficiency of LBA9402 was higher than A4 and MSU440 on A. tanguticus and A4 was better strain than MSU440 on P. tangutica. The hypocotyl explant was more suitable for P.tangutica and cotyledon explant was better for A.tangutica with a transformation frequency of 33.3% (P. tangutica) and 82.5% (A. tanguticus), respectively. In a flask reactor system, both the growth curves of HR for two species both appeared to be “S” curve; however, the HR of P. tangutica grew more rapidly than that of A. tanguticus, and the latter accumulated more biomass than the former. As the culture volume increased, the HR proliferation coefficient of both the species increased. HPLC analysis results showed that the content of TAs in the HR of P. tangutica was 257.24mg/100g·DW, which was more than that of A. tanguticus HR (251.08mg/100g·DW), and the anisodamine in the Pt- HR was significantly higher than that in At-HR. Moreover, tropane alkaloids in the HR of the two species were all significantly higher than that of the roots of aseptic seedlings.

Conclusion:

Our results suggest that HR of P. tangutica and A. tanguticus both could provide a useful platform for sustainable utilization of two Tibetan medicinal plants in the Qinghai-Tibetan Plateau in the future.

Establishment of hairy root cultures by Agrobacterium rhizogenes mediated transformation of Trachyspermum ammi L. for the efficient production of thymol

Trachyspermum ammi is an important medicinal plant that contains a bioactive compound namely thymol. In the study, T. ammi was transformed by Agrobacterium rhizogenes strains. Seedling stem explants were inoculated with A. rhizogenes strains A4, LBA 9402, ATCC 15834, and the effect of different co-cultivation media along with incorporation of acetosyringone (100 µM) was evaluated comparatively on the frequency of hairy root induction. The polymerase chain reaction using rolB and virD specific primers was served to confirm the putative transformed hairy roots. All strains established hairy root with various frequencies, among which strain ATCC 15834 was significantly the most efficient strain for hairy root induction (84.3%). Half-strength B5 medium and incorporation of acetosiryngone (100 µM) were also significantly optimal for hairy root induction. Hairy roots culture induced by ATCC 15834 using half-strength B5 liquid medium supplemented with 30 g L^-1 sucrose indicated the highest accumulation of biomass (99.05 g L^-1 FW and 10.95 g L^-1 DW) and thymol content (11.30 mg g^-1 DM) at 20 days. Nearly 4.9-fold and 5.3-fold increment of biomass and thymol accumulation was observed, respectively, at 20 days in comparison with the untransformed control roots. The results showed the high potential of T. ammi hairy roots for the biosynthesis of thymol.

Butterfly Pea (Clitoria ternatea), a Cyclotide-Bearing Plant With Applications in Agriculture and Medicine

The perennial leguminous herb Clitoria ternatea (butterfly pea) has attracted significant interest based on its agricultural and medical applications, which range from use as a fodder and nitrogen fixing crop, to applications in food coloring and cosmetics, traditional medicine and as a source of an eco-friendly insecticide. In this article we provide a broad multidisciplinary review that includes descriptions of the physical appearance, distribution, taxonomy, habitat, growth and propagation, phytochemical composition and applications of this plant. Notable amongst its repertoire of chemical components are anthocyanins which give C. ternatea flowers their characteristic blue color, and cyclotides, ultra-stable macrocyclic peptides that are present in all tissues of this plant. The latter are potent insecticidal molecules and are implicated as the bioactive agents in a plant extract used commercially as an insecticide. We include a description of the genetic origin of these peptides, which interestingly involve the co-option of an ancestral albumin gene to produce the cyclotide precursor protein. The biosynthesis step in which the cyclic peptide backbone is formed involves an asparaginyl endopeptidase, of which in C. ternatea is known as butelase-1. This enzyme is highly efficient in peptide ligation and has been the focus of many recent studies on peptide ligation and cyclization for biotechnological applications. The article concludes with some suggestions for future studies on this plant, including the need to explore possible synergies between the various peptidic and non-peptidic phytochemicals.

Advances in Boerhaavia diffusa hairy root technology: a valuable pursuit for identifying strain sensitivity and up-scaling factors to refine metabolite yield and bioactivity potentials

The present study reports the Agrobacterium rhizogenes-mediated hairy root induction in of an ethno-medicinally significant herb-Boerhaavia diffusa L., for elucidating the underlying competence regarding its biosynthetic (i.e. boeravinone B and eupalitin) and bioactivity (antibacterial, antioxidant and anti-inflammatory) potentials. Host plant-specific receptiveness towards A. rhizogenes strains and disparity in compatibility threshold of leaf and nodal explants were evident. Only leaf explants responded, attaining hairy root induction with the ATCC 15834 followed by A4 and SA79 strains in reducing order of transformation efficiency. The growth behaviours differed amongst independent rhizoclones, and two clones of A4 (RBH) and ATCC 15834 (RBT8) origin demonstrated higher growth potentials. Polymerase chain reaction amplification of rol genes confirmed their transformed nature. Optimization of the appropriate solvent and reverse phase high-performance liquid chromatography parameters relating to the targeted metabolite production in the selected RBH and RBT8 clones revealed higher accumulation of eupalitin with the RBH clone having the best result of 1.44 times greater yield over the control root. Compared to the selected rhizoclones, the control roots however showed higher boeravinone B content. Devising a modified "stirred-tank" reactor through equipping with marine impellers and ring spargers facilitated high-density RBH root biomass yield with 6.1-fold and 1.15-fold yield increment of the boeravinone B and eupalitin respectively compared to shake-flask cultures. Considering the control roots, the RBH clone revealed analogous antioxidant/antibacterial activities with improved anti-inflammatory potential. The hairy root mediated higher production of boeravinone B and eupalitin could be achieved for the first time in bioreactor.

High-performance liquid chromatographic quantification of plumbagin from transformed rhizoclones of Plumbago zeylanica L.: inter-clonal variation in biomass growth and plumbagin production

An optimized protocol for induction and establishment of Agrobacterium rhizogenes-mediated hairy root cultures of Plumbago zeylanica L. was developed through selection of suitable explant type and the bacterial strain. The infection of internodal explants from an in vivo plant and leaves of in vitro origin with the A4 strain resulted in the emergence of hairy roots at a transformation frequency of 86.33 and 42.33 %, respectively. Independent transformed root somaclones (rhizoclones) capable of sustained growth were maintained under a low illumination in auxin-free agar-solidified Murashige and Skoog (MS) medium through subcultures at periodic intervals. The presence of pRi T L-DNA rolB or rolC genes and pRi T R-DNA mas2 gene in the transformed rhizoclone genome was ascertained by PCR amplification. Concentrations and type of carbon source, auxin and media strength were optimized for root biomass growth. Five independent rhizoclones each from A4- and LBA9402-transformed root lines were studied for their plumbagin accumulation at different growth phases, using HPLC analysis. The potential for plumbagin biosynthesis was expressed in all the tested rhizoclones, although distinct inter-clonal variations were noted. It was evident that maturation of hairy roots was more important for plumbagin accumulation; slow-growing and early-maturing rhizoclones accumulated more plumbagin compared to fast-growing and late-maturing rhizoclones. A4-induced rhizoclone HRA2B5 was identified as the most superior clone with a higher plumbagin yield potential in comparison with other tested hairy root clones, in vitro-grown non-transformed roots and in vivo roots of naturally occurring P. zeylanica.

Production of triterpenoid anti-cancer compound taraxerol in Agrobacterium-transformed root cultures of butterfly pea (Clitoria ternatea L.)

Independent transformed root somaclones (rhizoclones) of butterfly pea (Clitoria ternatea L.) were established using explant co-cultivation with Agrobacterium rhizogenes. Rhizoclones capable of sustained growth were maintained under low illumination in auxin-free agar-solidified MS medium through subcultures at periodic intervals. Integration of T(L)-DNA rolB gene in the transformed rhizoclone genome was verified by Southern blot hybridization, and the transcript expression of T(R)-DNA ags and man2 genes was ascertained by reverse transcription polymerase chain reaction analysis. The major compound isolated and purified from the transformed root extracts was identified as the pentacyclic triterpenoid compound taraxerol using IR, (1)H-NMR, and (13)C-NMR spectroscopy. The taraxerol yield in cultured hairy roots, as quantified by HPTLC analysis, was up to 4-fold on dry weight basis compared to that in natural roots. Scanning of bands from cultured transformed roots and natural roots gave super-imposable spectra with standard taraxerol, suggesting a remarkable homology in composition. To date, this is the first report claiming production of the cancer therapeutic phytochemical taraxerol in genetically transformed root cultures as a viable alternative to in vivo roots of naturally occurring plant species.