Cloning and expression of key enzyme genes for chlorogenic acid synthesis in Chrysanthemum morifolium / 中草药

ABSTRACT

To investigate the effects of the expression of coumaroylquinate 3’-monooxygenase (C3’H) and shikimate O-hydroxycinnamoyltransferase (HCT) in the chlorogenic acid-producing pathway and active ingredients in Chrysanthemum morifolium under flooding stress, we cloned two C3’H genes which were CmC3’H1 and CmC3’H2 and two HCT genes which were CmHCT1 and CmHCT2 by the RT-PCR from Hangju and conducted bioinformatics analysis. During the flower bud differentiation stage, we flooded the C. morifolium and then used β-actin as the reference gene to detect the relative expression of the four genes by the qRT-PCR. Finally, the content of downstream products and other indicators of these four genes in C. morifolium were measured by HPLC. We obtained the four genes’ complete open reading frame and predicted the relative molecular mass of the amino acid sequence and the theoretical isoelectric point (pI). And the protein tertiary structure models were constructed. The qRT-PCR results showed that flooding the C. morifolium for 3 days during the flower bud differentiation stage resulted in significant expression changes of the four genes at different growth stages. The results of HPLC showed that chlorogenic acid, the downstream product catalyzed by the C3’H and the HCT, was significantly higher than that in the control group. It was also found that the content of luteoloside and 3,5-O-di-caffeoylquinic acid was also significantly higher than those of the control group. Therefore, C. morifolium regulates the synthesis of downstream products by regulating the expression of the four genes under flooding stress, thereby responding to flooding stress. And the flooding stress during flower bud differentiation can significantly enhance the accumulation of active ingredients of C. morifolium.