Effect of initial ammonium concentration on taxoid production and biosynthesis genes expression profile in suspension cultures of Taxus chinensis cells

摘要

The effect of initial ammonium concentration in medium on production of taxuyunnanine C (Tc) in suspension Cultures of U us chinensis was investigated. The results showed that the cell growth was reduced at an initial ammonium concentration of 2 mM when compared to the control (20 mM of initial ammonium in medium), but interestingly the Tc content was enhanced by two fold to 8.07 mg/g DW. The transcription of a couple of key genes in taxoid biosynthetic pathway was investigated by quantitative real-time PCR to understand why Tc biosynthesis was improved at the low initial medium ammonium (2 mM). It was found that the transcription level of genes of geranylgeranyl diphosphate synthase, taxadiene synthase, taxadiene 5 alpha-hydroxylase, taxadiene 5 alpha-ol O-acetyltransferase, taxane 10 beta-hydroxylase and taxadiene 13 alpha-thydroxylase were all induced in the early stage of cultivation at 2 mM of initial ammonium compared to the control (20 mM of initial ammonium). The stimulation of secondary metabolite synthesis by a lower ammonium concentration may be resulted from the ammonium deficiency-induced transcription of Tc biosynthetic genes.