The PcbZIP44 transcription factor inhibits patchoulol synthase gene expression and negatively regulates patchoulol biosynthesis in Pogostemon cablin

Patchouli alcohol (patchoulol), a sesquiterpenoid specifically synthesized by herbal plant Pogostemon cablin, has a variety of pharmacological and biological activities and is widely utilized in the medical and cosmetic industries. However, there are few studies on the transcriptional modulation of patchoulol biosynthesis. Some studies have reported that basic leucine zipper (bZIP) transcription factors (TFs) participate in the biosynthesis of plant terpenoids, but there is no report that bZIP TFs are involved in the modulation of patchoulol biosynthesis. This study was conducted to explain the regulation of patchoulol biosynthesis by PcbZIP44, a bZIP TF identified in patchouli for the first time. PcbZIP44 was highly expressed in roots and stems, and its encoded protein was nuclear localized revealed by protoplast subcellular localization experiment. According to the results of the transient dual-luciferase assay and yeast one-hybrid (Y1H) assays, PcbZIP44 can bind to the PcPTS (patchoulol synthase) gene promoter to repress its activity. Overexpression of the PcbZIP44 gene significantly reduced the content of patchoulol and resulted in a significant down-regulation of the PcPTS gene at the transcriptional level. Correspondingly, virus-induced PcbZIP44 gene silencing (VIGS) significantly increased the content of patchoulol and resulted in a significant up-regulation of the PcPTS gene at the transcriptional level. Therefore, these results suggested that PcbZIP44 negatively regulates patchoulol biosynthesis by inhibiting the PcPTS gene in P. cablin.