Light-responsive transcription factor ApTrihelix1 modulates andrographolide biosynthesis via targeting ApCPS2 in Andrographis paniculata.

Andrographolide (AD) is the major bioactive component in the Chinese medicinal plant Andrographis paniculata (A. paniculata), which is widely used for its anti-inflammatory and antiviral properties. In this study, we observed that light is a critical environmental factor for AD biosynthesis and identified a potential transcription factor, ApTrihelix1, as a regulator of AD biosynthesis via RNA-seq combined with co-expression analysis. ApTrihelix1 is light-induced, and knocking down its expression downregulates AD content as well as the expression of several AD biosynthesis-related genes (ADRGs). Furthermore, through high-throughput sequencing methods (e.g. ChIP-seq) and molecular experiments (e.g. Yeast One Hybrid assay), ApTrihelix1 was found to bind to the promoter of ApCPS2 (a key ADRG) to activate its expression. Taken together, these data strongly support that light upregulates the expression of certain transcription factors (e.g. ApTrihelix1), thereby activating key ADRGs (e.g. ApCPS2) and promoting AD accumulation in A. paniculata.