Longitudinal expression profiles of flavonoid synthesis-related genes and their correlations with contents of flavonoids including anthocyanins in purplish-green aerial stems of Panax notoginseng

Purplish-green aerial stems of Panax notoginseng hold golden section-typed purpling due to the longitudinally local accumulation of flavonoids including anthocyanins. However, the longitudinal expression profiles of the flavonoid synthesis-related structural genes (SGs) and transcription factor genes ( TF s) of P. notoginseng and their correlations with the flavonoid accumulation in the stems remain unknown. In this study, quantitative real-time PCR indicated the top-to-base longitudinal transcriptional levels of the essential SGs (i.e., CHS 2 , CHI 1 , F3H , DFR , ANS , and 3GT ) and TF s (i.e., bHLH 1 , bHLH 3 , MYB 1 , MYB 2 , MYB 3 , WD40 1 , WD40 2 and WD40 3 ) displayed various multi-peak curves. Spectrophotometry revealed the total flavonoid content (TFC) and total anthocyanin content (TAC) both displayed asymmetric single-peak curves whose highest peaks appeared at the eighth and seventh stem segments, respectively, and microscopic detection illustrated the anthocyanins concentrated in the upper parts of the stems. Meanwhile, the correlations between the transcriptional levels of the SGs and TF s and the TFC and TAC were highly diverse. Collectively, our findings suggest that, for the synthesis of the flavonoids including anthocyanins in the stems, the SGs and TF s may not organize into a cotranscription group, the CHI 1 and ANS are the foremost SGs, bHLH 3 , MYB 1 and WD40 3 are the main TF s and bHLH 1 plays a negative regulatory role, which can provide a reference for the molecular breeding of P. notoginseng .