A Preliminary Study On The Changes Of Catalpol Content And The Expression Of Key Enzyme Gene In Terpene Synthesis In

Catalpol is the major bioactive component in Rehmannia glutinosa and has been proved to play an important role in diabetes and nerve repair. In this study, we assayed the contents of catalpol and total iridoid glycosides in various tissues of Wen85-5by HPLC and specteophotometric methods, respectively. We examined the tissue-and temporal expression pro filings of41putative genes from10gene families (enzymes) which are involved in monoterpene biosynthetic pathway, in Rehmanniae glutinosa by real time-qPCR. This work will provide the theoretical basis for terpeneoid biosynthesis. The major results were summarized as follows:1. Dynamic changes of catalpol and total iridoid glycosides in the different ages of leaves, petioles, stem, sizes of roots of R.glutinosa. The analysis on2012and2013samples found that the contents of catalpol and total iridoid glycosides decreased with the increase of the leaf and petiole age, tender leaves and petioles having the highest content; the bigger the root diameter is, the higher contents of the effective components are; The contents of catalpol in stem increased by two-three times in September than in August. The catalpol content in the studied tissues was positively correlated with the total iridoid content.2. RT-qPCR results of41monoterpene biosynthesis-related genes in16tissues revealed that the expression levels of AACT (first enzyme) and HMGR (key enzyme) genes in the MVA pathway upstream of terpenoid biosynthesis pathway did not vary in studied various tissues of R. glutinosa in August and September,2012, the expression levels did not correspond with the content of iridoid. However,9genes including DXS3, DXS5, DXS9, DXR11, DXR3, DXR4, HDR1, HDR11and HDR2, participating in MEP pathway, were found to increase their expression levels in certain ages of leaves in September, compared with August, the expression level of RgDXR3was correlated with the contents of catalpol and total iridoid glycoside glutinosa. GPPS.SSU is a rate-limiting enzyme in monoterpene biosynthesis, the expression levels of GPPS.LSU2and GPPS.SSU were significantly correlated with the content of iridoid. Geraniol10-hydroxylase is identified as a key enzyme in iridoid biosynthesis pathway, GI0H1and G10H2were expressed highly in leaves but in other tissues at a lower or undetectable level, the relation between the expression levels of G10H and the content of iridoid needed to be further discussed.