Comparative study of withanolide production and the related transcriptional responses of biosynthetic genes in fungi elicited cell suspension culture of Withania somnifera in shake flask and bioreactor

Ashwagandha (Withania somnifera) is one of the most reputed medicinal plants in the traditional medicinal system. In this study, cell suspension culture of W. somnifera was elicited with cell homogenates of fungi (A. alternata, F. solani, V. dahliae and P. indica) in shake flask and the major withanolides like withanolide A, withaferin A and withanone were analysed. Simultaneously expression levels of key pathway genes from withanolides biosynthetic pathways were also checked via quantitative PCR in shake flask as well as in bioreactor. The results show that highest gene expression of 10.8, 5.8, 4.9, and 3.3 folds were observed with HMGR among all the expressed genes in cell suspension cultures with cell homogenates of 3% P. indica, 5% V. dahliae, 3% A. alternata and 3% F. solani, respectively, in comparison to the control in shake flask. Optimized concentration of cell homogenate of P. indica (3% v/v) was added to the growing culture in 5.0-l bioreactor under optimized up-scaling conditions and harvested after 22 days. The genes of MVA, MEP and withanolides biosynthetic pathways like HMGR, SS, SE, CAS, FPPS, DXR and DXS were up-regulated by 12.5, 4.9, 2.18, 4.65, 2.34, 1.89 and 1.4 folds, respectively in bioreactor. The enhancement of biomass (1.13 fold) and withanolides [withanolide A (1.7), withaferin A (1.5), and withanone (1.5) folds] in bioreactor in comparison to shake flask was also found to be in line with the up-regulation of genes of withanolide biosynthetic pathways.

Micromorphology, histochemistry and ultrastructure of the foliar trichomes of Withania somnifera (L.) Dunal (Solanaceae)

The leaves of Withania somnifera contained four morphologically distinct trichome types: glandular capitate, non-glandular dendritic (branched), non-glandular bicellular and non-glandular multicellular trichomes. Major phytochemical compounds present within glandular and non-glandular trichomes were alkaloids and phenolic compounds. The aim of this study was to characterize the micromorphology of the foliar trichomes of Withania somnifera as well as to elucidate the location and composition of the secretory products. Trichome density and length was also determined in three developmental stages of the leaves. Light microscopy and scanning electron microscopy showed the presence of four morphologically distinct trichome types: glandular capitate, non-glandular dendritic, non-glandular bicellular and non-glandular multicellular. The dendritic trichomes exhibited cuticular warts which are involved in the "Lotus-Effect". Glandular capitate and non-glandular dendritic trichomes were aggregated on the mid-vein of young and mature leaves, possibly to protect underlying vasculature. Histochemical staining also revealed the presence of two major classes of phytochemical compounds that are of medicinal importance, i.e. alkaloids and phenolic compounds. These compounds are used to treat a wide variety of ailments and also act as chemical deterrents in plants. The results of this study explain possible roles of four morphologically distinct trichome types based on their morphology, foliar distribution and content.

Withanolides from Withania somnifera Dunal: development of cellular technology and their production

Withania somnifera Dunal is one of the most commonly used plants in Ayurvedic and indigenous system of medicine in India for over thousands of years. In view of its varied therapeutic potential, the plant has also been the subject of considerable scientific attention. The major chemical constituents of the Withania genus, the withanolides, are a group of naturally occurring C28-steroidal lactones built on an intact or rearranged ergostane framework, in which C22 and C26 are oxidized to form a six-member lactone ring. In recent years, numerous pharmacological investigations have been carried out utilizing W. somnifera extracts and several patents have been filed on pharmacological and medicinal importance of withanolides and extracts of W. somnifera, individually or in combination. Considering the immense importance of withanolides for medicinal purposes, the establishment of strategies to improve withanolides yield are highly desirable. Under natural conditions, W. somnifera possesses restricted levels of withanolides then, alternatives for obtaining withanolides in better yields are imperative. In vitro approaches followed by metabolic engineering could be attractive tools to achieve this goal. Therefore, we present here an overview of the development of various protocols for in vitro tissue regeneration from W. somnifera and in vitro secondary metabolite production as well. The review also gives an account of selected patents on various important activities of phytochemicals and extracts of W. somnifera.

A promising approach on biomass accumulation and withanolides production in cell suspension culture of Withania somnifera (L.) Dunal

Withanolide is one of the most extensively exploited steroidal lactones, which are biosynthesized in Withania somnifera. Its production from cell suspension culture was analyzed to defeat limitations coupled with its regular supply from the plant organs. In order to optimize the different factors for sustainable production of withanolides and biomass accumulations, different concentrations of auxins or cytokinins and their combinations, carbon sources, agitation speed, organic additives and seaweed extracts was studied in cell suspension culture. Maximum biomass accumulation (16.72 g fresh weight [FW] and 4.18 g dry weight [DW]) and withanolides production (withanolide A 7.21 mg/g DW, withanolide B 4.23 mg/g DW, withaferin A 3.88 mg/g DW and withanone 6.72 mg/g DW) were achieved in the treatment of Gracilaria edulis extract at 40 % level. Organic additive L-glutamine at 200 mg/l in combination with picloram (1 mg/l) and KN (0.5 mg/l) promoted growth characteristics (11.87 g FW and 2.96 g DW) and withanolides synthesis (withanolide A 5.04 mg/g DW, withanolide B 2.59 mg/g DW, withaferin A 2.36 mg/g DW and withanone 4.32 mg/g DW). Sucrose at 5 % level revolved out to be a superior carbon source yielded highest withanolides production (withanolide A 2.88 mg/g DW, withanolide B 1.48 mg/g DW, withaferin A 1.35 mg/g DW and withanone 2.47 mg/g DW), whereas biomass (7.28 g FW and 1.82 g DW) was gratefully increased at 2 % level of sucrose in cell suspension culture. This optimized protocol can be utilized for large scale cultivation of W. somnifera cells in industrial bioreactors for mass synthesis of major withanolides.

Plant hormones including ethylene are recruited in calyx inflation in Solanaceous plants

Plant hormones direct many processes of floral and post-floral morphogenesis in Angiosperms. However, their role in shaping floral morphological novelties, such as inflated calyx syndrome (ICS) exhibited by a few genera of the Solanaceae, remains unknown. In Withania and Physalis, sepals resume growth after pollination and encapsulate the mature fruit to form a balloon-like structure, i.e. ICS. The epidermal cells of calyx show enlargement and lobation post-fertilization. Application of hormones to depistillated flower buds of Withania revealed that cytokinins and gibberellins mimic fertilization signals. The ICS development is a synchronous step with fruit development; both processes are under the control of more or less the same set of hormones, including cytokinins and gibberellic acids. Interestingly, inhibition of ethylene in the system is sufficient to yield inflated calyx in Withania. In contrast, Tubocapsicum, a closely related species and an evolutionary natural loss mutant of ICS - showed no response to applied hormones, and ethylene led to inflation of the receptacle indirectly. In addition to hormones, the expression of an MPF2-like MADS-box transcription factor in sepals is essential for ICS formation. Nevertheless, the interactions between MPF2-like genes and hormones are barely detectable at the transcript level. Our data provide insight into the role of hormones in generating floral morphological diversity during evolution.

Establishment of cell suspension cultures of Withania somnifera for the production of withanolide A

Cell suspension cultures of Withania somnifera were established in shake flasks and the effect of different growth regulators (auxins, combination of auxin and cytokinin), inoculum density (2.5-20 g L(-1)), different media (MS, B5, NN and N6), the strength of the MS medium (0.25-2.0 x), carbon source (sucrose, glucose, fructose, maltose), concentration of the sucrose (1-8% (w/v)) and the initial pH (4.0-6.5) of the medium were determined for the production of withanolide A. The optimized conditions for biomass accumulation and withanolide A production were found to be 10 g L(-1) of the inoculum on fresh weight basis, the full strength MS medium, 3% (w/v) sucrose, four weeks culture period and the initial medium pH of 5.8. The results of present study are useful for scale-up process.

Establishment of Withania somnifera hairy root cultures for the production of withanolide A

Withania sominifera (Indian ginseng) was transformed by Agrobacterium rhizogenes. Explants from seedling roots, stems, hypocotyls, cotyledonary nodal segments, cotyledons and young leaves were inoculated with A. rhizogenes strain R1601. Hairy (transformed) roots were induced from cotyledons and leaf explants. The transgenic status of hairy roots was confirmed by polymerase chain reaction using nptII and rolB specific primers and, subsequently, by Southern analysis for the presence of nptII and rolB genes in the genomes of transformed roots. Four clones of hairy roots were established; these differed in their morphology. The doubling time of faster growing cultures was 8-14 d with a fivefold increase in biomass after 28 d compared with cultured, non-transformed seedling roots. MS-based liquid medium was superior for the growth of transformed roots compared with other culture media evaluated (SH, LS and N6), with MS-based medium supplemented with 40 g/L sucrose being optimal for biomass production. Cultured hairy roots synthesized withanolide A, a steroidal lactone of medicinal and therapeutic value. The concentration of withanolide A in transformed roots (157.4 microg/g dry weight) was 2.7-fold more than in non-transformed cultured roots (57.9 microg/g dry weight).