Effects of elicitors from culture filtrate of CL105 on flavonoid production of s calli.

Introduction: Endophytic fungi can promote secondary metabolite accumulation in medicinal plants. Previously, we observed that the culture filtrate of CL105 promoted flavonoid production in calli. However, the active ingredients and mechanisms associated with this secondary metabolite accumulation remain unclear.

Methods: This study evaluates the effects of different elicitors from the culture filtrate of CL105 namely, exopolysaccharide (EPS), exoprotein (EP), and other parts (OP), on the flavonoid production in calli by HPLC. Subsequently, the underlying mechanism of EPS induced flavonoid production in calli was revealed by transcriptomics and RT-PCR.

Results And Discussion: The results indicated a significant increase in flavonoid production in calli following treatment with EPS. Baicalin (1.40 fold), wogonoside (1.91 fold), and wogonin (2.76 fold) were most significantly up-regulated compared with the control. Transcriptome analysis further revealed up-regulation of key enzyme genes (, and ) involved in flavonoid synthesis after 5 days of EPS treatment. Moreover, the expression of and -genes involved in gibberellin acid (GA) and abscisic acid biosynthesis (ABA), respectively-were significantly up-regulated. The expression levels of certain transcription factors, including , and , were also significantly higher than in controls. Our results indicated that EPS was a main active elicitor involved in promoting flavonoid production in calli. We postulated that EPS might stimulate the expression of , and , leading to markedly upregulated , and expression levels, ultimately promoting flavonoid synthesis. This study provides a novel avenue for large-scale in vitro production of flavonoids in .