Abstract
Whereas higher plants commonly produce phenylpropanoids, limited plant species produce alkaloids. Among alkaloids isoquinoline alkaloids are a major group and its biosynthetic pathway has been intensively investigated at the molecular level. Especially, berberine biosynthesis in Coptis japonica (Ranunculaceae) has been well characterized and a general transcriptional factor, i.e. CjWRKY1 was isolated (Kato et al. , 2007). Here, we report the isolation and characterization of another general transcriptional factor, CjbHLH1. CjbHLH1 was isolated using transient RNAi analysis as CjWRKY1. However, the transient overexpression of CjbHLH1 decreased the expression of berberine biosynthetic genes. To characterize the functionality of CjbHLH1, we analyzed subcellular localization of CjbHLH1 using GFP fusion construct and its transcriptional activity with biosynthetic gene promoter::luciferase reporter gene (pLUC). Transient expression of CjbHLH1:GFP in Cj protoplasts confirmed nuclear localization of CjbHLH1. Further transient assay using pLUC reporter indicates the transcriptional activity of CjbHLH1. Isolation of CjbHLH1-interacting factors is on going.
