UV-B-induced signaling events leading to enhanced-production of catharanthine in Catharanthus roseus cell suspension cultures.
BACKGROUND
Elicitations are considered to be an important strategy towards improved in vitro production of secondary metabolites. In cell cultures, biotic and abiotic elicitors have effectively stimulated the production of plant secondary metabolites. However, molecular basis of elicitor-signaling 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 tryptophan decarboxylase (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 of catharanthine 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 Str were inhibited by 3-4 fold upon pretreatment of various inhibitors like suramin, N-acetyl cysteine, inhibitors of calcium fluxes, staurosporine etc.


CONCLUSIONS
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.
Ramani
Shilpa
S
Department of Biochemistry, Indian Institute of Science, Bangalore, 560012, India. shilpasuhas@gmail.com
Chelliah
Jayabaskaran
J
D000970:Antineoplastic Agents / Q000494:pharmacology; D001142:Aromatic-L-Amino-Acid Decarboxylases / Q000235:genetics / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D002135:Calcium-Binding Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D019759:Carbon-Nitrogen Lyases / Q000235:genetics / Q000378:metabolism; D030008:Catharanthus / Q000235:genetics / Q000378:metabolism* / Q000528:radiation effects*; D002478:Cells, Cultured; D003470:Culture Media / Q000528:radiation effects; D015870:Gene Expression / Q000187:drug effects; D006861:Hydrogen Peroxide / Q000037:antagonists & inhibitors / Q000378:metabolism; D006863:Hydrogen-Ion Concentration / Q000187:drug effects; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D010766:Phosphorylation; D010940:Plant Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D011494:Protein Kinases / Q000378:metabolism; D015398:Signal Transduction / Q000528:radiation effects*; D013498:Suramin / Q000494:pharmacology; D014158:Transcription, Genetic / Q000528:radiation effects; D014466:Ultraviolet Rays; D014748:Vinca Alkaloids / Q000096:biosynthesis*
D000970:Antineoplastic Agents; D002135:Calcium-Binding Proteins; D003470:Culture Media; D010940:Plant Proteins; D014748:Vinca Alkaloids; D013498:Suramin; D006861:Hydrogen Peroxide; D011494:Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D001142:Aromatic-L-Amino-Acid Decarboxylases; D019759:Carbon-Nitrogen Lyases; C022684:strictosidine synthetase; D002118:Calcium; C017836:catharanthine