A Survey On The Molecular Mechanism Of Light Regulating The Andrographolide Biosynthesis

Andrographis paniculata is a widely used traditional Chinese medicine,and its main medicinal active ingredient,andrographolide,has important anti-inflammatory and antiviral effects.Hence,the content of andrographolide is an important quality indicator of the herbal raw material of A.paniculata.Light is an important environmental factor that provides the energy and material basis for plant growth and development,and also acts as a signal to directly regulate the biosynthesis of plant secondary metabolites.In our group’s preliminary research,it was found that light is a necessary condition for the biosynthesis of andrographolide in A.paniculata.However,the mechanisms by which the biosynthesis of andrographolide is regulated by light are still less well studied,e.g.the light-responsive transcription factors and its regulatory networks remain unclear,which limits the further development of the subsequent application of light to improve the andrographolide content and the quality of the herbal raw material of A.paniculata.Therefore,an etiolated seedlings system of A.paniculata was established and a further study was conducted on light regulating andrographolide biosynthesis through comparative transcriptomics,with the following main results:(1)Light significantly influenced andrographolide content.The andrographolide content significantly increase with the increasing light duration.(2)Transcriptome analysis revealed that the expression levels of andrographolide biosynthetic genes significantly differed under different light treatments,with the expression of 15 andrographolide biosynthesis pathway genes being significantly up-regulated by prolonged light exposure,suggesting that these genes are involved in the regulation of andrographolide biosynthesis by light.(3)Furthermore,by comparing the transcriptomics,such as co-expression analysis,transcriptional regulatory network construction and Motif analysis of promoters,many potential light-responsive transcription factors,such as b HLH,b ZIP,and Trihelix,were identified.For example,Trihelix transcription factor is a coexpressed gene of Ap CPS2 gene(a key gene in the biosynthetic pathway of andrographolide)and has a typical Motif of Trihelix transcription factor on the Ap CPS2 gene promoter,suggesting that Trihelix is a key factor in regulating Ap CPS2 gene expression and promoting andrographolide biosynthesis during the light response.In conclusion,based on transcriptomic analysis,this study investigated the potential mechanism of light duration on the regulation of andrographolide biosynthesis,which provides an important theoretical basis for further changes in cultivation condition through greenhouse light control to improve the medicinal quality of A.paniculata raw materials.