Effect of Three Plant Hormone Elicitors on the Camptothecin Accumulation and Gene Transcript Profiling in Camptotheca Acuminata Seedlings

Camptothecin (CPT) is an antitumor alkaloid first isolated from Chinese tree Camptotheca acuminata Decaisne (Nyssaceae). Several attempts have been made to improve CPT production in plant, among which elicitation was considered as a useful method. In this study, camptothecin (CPT) and its derivative 10-hydroxycamptothecin (HCPT) accumulation, as well as related gene transcript proi¬ling in C. acuminata seedlings, in response to abscisic acid (ABA, 100 µM), methyl jasmonate (MJ, 100 µM) and salicylic acid (SA, 1 mM) were examined. Results showed that all three elicitors enhanced both camptothecin and 10-hydroxycamptothecin accumulation, among which abscisic acid (ABA) exhibited the most effective elicitation with the increment of 1.44-fold for CPT (1.81 mg/g DW) and 1.21-fold for HCPT (2.6 mg/g DW) respectively. Our expression results showed a positive correlation between gene expression and alkaloid accumulation, suggesting that alkaloid accumulation may be the result of the synchronous up-regulation of several genes such as 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGR), 1-deoxy-D-xylulose 5-phosphate reductoisomerase (DXR) and tryptophan decarboxylase (TDC) involved in CPT biosynthesis under the treatment of various elicitors. Our work provided useful information of further understanding molecular regulation mechanism of CPT biosynthesis and its metabolic engineering in C. acuminata in the future.