DNA Methylation Influences Chlorogenic Acid Biosynthesis in Lonicera japonica by Mediating LjbZIP8 to Regulate Phenylalanine Ammonia-Lyase 2 Expression

The content of active compounds differ in buds and flowers of (FLJ) and var. chinensis (rFLJ). Chlorogenic acid (CGAs) were major active compounds of and regarded as measurements for quality evaluation. However, little is known concerning the formation of active compounds at the molecular level. We quantified the major CGAs in FLJ and rFLJ, and found the concentrations of CGAs were higher in the buds of rFLJ than those of FLJ. Further analysis of CpG methylation of CGAs biosynthesis genes showed differences between FLJ and rFLJ in the 5'-UTR of phenylalanine ammonia-lyase 2 ( ). We identified 11 proteins and 24 proteins with conserved basic leucine zipper domains, subcellular localization, and electrophoretic mobility shift assay showed that the transcription factor LjbZIP8 is a nuclear-localized protein that specifically binds to the G-box element of the 5'-UTR. Additionally, a transactivation assay and overexpression in transgenic tobacco indicated that LjbZIP8 could function as a repressor of transcription. Finally, treatment with 5-azacytidine decreased the transcription level of and CGAs content in FLJ leaves. These results raise the possibility that DNA methylation might influence the recruitment of LjbZIP8, regulating expression level and CGAs content in .