Transcriptomic Analysis of Cyclamen persicum to Identify Invovled Genes in Triterpene Secondary Metabolites Pathway

Saponins are considered as a diverse group of natural active compounds, which are widely found in crops. Mevalonate pathway (MVA) is regarded as the main pathway for synthesis of saponins in crops. This study aims to compare transcriptome of the leaf with tuber of crop including tubers and roots. First, more than 166 million reads were generated. The existence of 36,678 unigenes in the two samples out of 48,936 assembled ones showed a significant difference in expression. Finally, 310 and 290 highly up-regulated genes in leaf and tuber were selected for the next analysis. In addition, the expression profiles of 13 key genes in the MVA pathway were compared in RNA sequencing and reverse transcription-quantitative polymerase chain reaction analysis. The results indicated that cyclamen tuber has a higher level of expression of MVA pathway genes. The topological analysis for gene co-expression network involved in triterpenoid synthesis represented that the genes at the beginning of such pathway play a critical role so that the reduction of their expression challenges triterpenoid synthesis severely. The tuber of the cyclamen appears to be the major site of triterpene synthesis, and transfer of excess Isopentenyl pyrophosphate (IPP) from tuber to leaf activates downstream genes in leaf of crop.