UV-B-induced signaling events leading to enhanced-production of catharanthine in Catharanthus roseus cell suspension cultures
Shilpa Ramani and Jayabaskaran Chelliah*
Address: Department of Biochemistry, Indian Institute of Science, Bangalore, 560012, India Email: Shilpa Ramani - email@example.com; JayabaskaranChelliah* - firstname.lastname@example.org * Corresponding author
Published: 7 November 2007 BMC Plant Biology 2007, 7:61 doi:10.1186/1471-2229-7-61
Received: 13 November 2006 Accepted: 7 November 2007
This article is available from: http://www.biomedcentral.com/1471-2229/7/61 © 2007 Ramani and Chelliah; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of theCreative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Background: Elicitations are considered to be an important strategy towards improved in vitro production of secondary metabolites. In cell cultures, biotic and abiotic elicitors haveeffectively stimulated the production of plant secondary metabolites. However, molecular basis of elicitorsignaling cascades leading to increased production of secondary metabolites of plant cell is largely unknown. Exposure of Catharanthus roseus cell suspension culture to low dose of UV-B irradiation was found to increase the amount of catharanthine and transcription of genes encoding tryptophandecarboxylase (Tdc) and strictosidine synthase (Str). In the present study, the signaling pathway mediating UV-B-induced catharanthine accumulation in C. roseus suspension cultures were investigated. Results: Here, we investigate whether cell surface receptors, medium alkalinization, Ca2+ influx, H2O2, CDPK and MAPK play required roles in UV-B signaling leading to enhanced production ofcatharanthine in C. roseus cell suspension cultures. C. roseus cells were pretreated with various agonists and inhibitors of known signaling components and their effects on the accumulation of Tdc and Str transcripts as well as amount of catharanthine production were investigated by various molecular biology techniques. It has been found that the catharanthine accumulation and transcription of Tdc and Strwere inhibited by 3–4 fold upon pretreatment of various inhibitors like suramin, N-acetyl cysteine, inhibitors of calcium fluxes, staurosporine etc. Conclusion: Our results demonstrate that cell surface receptor(s), Ca2+ influx, medium alkalinization, CDPK, H2O2 and MAPK play significant roles in UV-B signaling leading to stimulation of Tdc and Str genes and the accumulation of catharanthine in C.roseus cell suspension cultures. Based on these findings, a model for signal transduction cascade has been proposed.
C. roseus produces terpenoid indole alkaloids (TIAs) as a part of its secondary metabolism. TIAs provide protection against microbial infection, herbivores and abiotic environmental stresses such as UV irradiation [1,2]. Some of the TIAs are of pharmaceuticalimportance such as the antitumor dimeric alkaloids, vincristine and vinblastine,
and the anti-hypertensive monomeric alkaloids, ajmalicine and serpentine . The anti-tumor dimeric alkaloids, which accumulate in the leaves of C. roseus, are composed of catharanthine and vindoline monomers and are exclusively found in C. roseus plants. In plants, the dimeric alkaloids and the monomer catharanthineaccumulate in low amounts whereas the monomer vindoline accumulates at
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BMC Plant Biology 2007, 7:61
a relatively higher level [4,5]. C. roseus cell cultures have been investigated as alternative means of production of terpenoid indole alkaloids, but they failed to produce vindoline ....