Plant cell cultures: Chemical factories of secondary metabolites

In the growth condition(s) of plants, numerous secondary metabolites (SMs) are produced by them to serve variety of cellular functions essential for physiological processes, and recent increasing evidences have implicated stress and defense response signaling in their production. The type and concentration(s) of secondary molecule(s) produced by a plant are determined by the species, genotype, physiology, developmental stage and environmental factors during growth. This suggests the physiological adaptive responses employed by various plant taxonomic groups in coping with the stress and defensive stimuli. The past recent decades had witnessed renewed interest to study abiotic factors that influence secondary metabolism during in vitro and in vivo growth of plants. Application of molecular biology tools and techniques are facilitating understanding the signaling processes and pathways involved in the SMs production at subcellular, cellular, organ and whole plant systems during in vivo and in vitro growth, with application in metabolic engineering of biosynthetic pathways intermediates.

/pdf/stress-and-defense-responses-in-plant-secondary-metabolites-29akr1xmji.pdf

Stress and defense responses in plant secondary metabolites production

Hairy root research: recent scenario and exciting prospects.

"Hairy root" systems, obtained by transforming plant tissues with the "natural genetic engineer" Agrobacterium rhizogenes, have been known for more than three decades. To date, hairy root cultures have been obtained from more than 100 plant species, including several endangered medicinal plants, affording opportunities to produce important phytochemicals and proteins in eco-friendly conditions. Diverse strategies can be applied to improve the yields of desired metabolites and to produce recombinant proteins. Furthermore, recent advances in bioreactor design and construction allow hairy root-based technologies to be scaled up while maintaining their biosynthetic potential. This review highlights recent progress in the field and outlines future prospects for exploiting the potential utility of hairy root cultures as "chemical factories" for producing bioactive substances.

Hairy root type plant in vitro systems as sources of bioactive substances

https://www.cell.com/trends/biotechnology/pdf/S0167-7799(06)00181-8.pdf

Harnessing the potential of hairy roots: dawn of a new era

Caulogenic responses of various explant types from 12-month-old plants of Hemidesmus indicus were tested Second and third visible nodes (05 cm) from the apex and root segments (05 cm) were the most and least regenerative respectively, with the formation of 937 and 26 shoots in 4 weeks on half strength MS medium supplemented with 222 μM BA and 107 μM NAA and 444 μM BA and 269 μM NAA respectively Caulogenic ability of the nodes decreased with increasing maturity Shoot buds initiated upon the young nodes on day 10 developed into 72 cm long shoots within 4 weeks thereby making a shoot elongation phase unnecessary Nodal explants of the in vitro raised shoots subcultured in the same medium produced 932 shoots of 71 cm length in 3–4 weeks, similar to those of the mature plant-derived nodes Multiplication through subculture of the nodes up to 25 passages of 4 weeks each was achieved without decline Shoot cultures were rooted in quarter salt strength MS medium containing 98 μM IBA and the rooted plants were hardened for establishment in pots at 96% rate Four months after establishment, the micropropagated plants were stable and showed uniform morphological and growth characteristic After 12 months of cultivation in the field, on an average micropropagated plant consisted of 4–5 shoots, 5–8 branches per shoot and increased root biomass (135 g) compared to the poor growth (single shoot and 2–3 branches) and root production (46 g) values obtained with plants raised from conventional rooted stem cuttings The concentration of the root specific compound, 2-hydroxy 4-methoxy benzaldehyde per plant was 2–3 fold higher in micropropagated plants though on unit dry root biomass (012% per g dry wt) basis it remained the same between two sources of plants

Micropropagation of Hemidesmus indicus for cultivation and production of 2-hydroxy 4-methoxy benzaldehyde

Hairy roots of Rauvolfia micrantha were induced from hypocotyl explants of 2–3 weeks old aseptic seedlings using Agrobacterium rhizogenes ATCC 15834. Hairy roots grown in half-strength Murashige & Skoog (MS) medium with 0.2 mg indole 3-butyric acid l−1 and 0.1 mg α-naphthaleneacetic acid l−1 produced more ajmaline (0.01 mg g−1 dry wt) and ajmalicine (0.006 mg g−1 dry wt) than roots grown in auxin-free medium. Ajmaline (0.003 mg g−1 dry wt) and ajmalicine (0.0007 mg g−1 dry wt) were also produced in normal root cultures. This is the first report of production of ajmaline and ajmalicine in hairy root cultures of Rauvolfia micrantha.

Production of ajmalicine and ajmaline in hairy root cultures of Rauvolfia micrantha Hook f., a rare and endemic medicinal plant

Nodal explants of Hemidesmus indicus plants cultured in half strength Murashige and Skoog medium fortified with 2 mg indole-3-butyric acid l−1 in the dark produced 10–12 roots (1–2 cm) with minimal callusing in 10 days. Roots, ∼20 mg dry wt, cultured in Gamborg et al. medium supplemented with 2 mg IBA l−1, sucrose (4% w/v), pH (5.6) and agitation (70 rpm) in the dark yielded 550 mg root dry wt/flask and 0.18% 2-hydroxy 4-methoxy benzaldehyde in the roots after 30 days. The maintenance of normal morphology of the roots, consistent biomass and product yields over a 21-month period indicated the stability of the cultures. © Rapid Science Ltd. 1998

S. Seeni

Papers

Micropropagation of Hemidesmus indicus for cultivation and production of 2-hydroxy 4-methoxy benzaldehyde

Production of ajmalicine and ajmaline in hairy root cultures of Rauvolfia micrantha Hook f., a rare and endemic medicinal plant

Production of 2-hydroxy 4-methoxy benzaldehyde using root cultures of Hemidesmus indicus