Transcriptome analysis and discovery of genes related to andrographolide synthesis of Andrographis paniculata under UV-C treatment

【Objective】Transcriptome sequencing was performed on the leaves of Andrographis paniculata treated with ultraviolet C(UV-C),and the genes related to andrographolide synthesis were excavated to provide reference for further exploring the regulatory mechanism and biological functions of andrographolide synthesis-related genes.【Method】 A.paniculata seedlings grown for 60 days were selected as experimental materials. After 2 h of UV-C irradiation,their transcriptome was sequenced using the 2^nd-generation sequencing platform,andwith bioinformatics software and qRTPCR, the sequence were evaluated by gene expression analysis and functional annotation to identify genes related to andrographolide synthesis in response to UV-C.【Result】A total of 21545 A.paniculata genes were annotated,and 2137 genes showed significant differential expression(SDE)patterns. Among them,1147 genes were significantly up-regulated and 990 genes were significantly down-regulated. GO annotation results showed that UV-C treatment caused oxidative stress,and the expression of NADH dehydrogenase genes in mitochondrial oxidative phosphorylation electron transport chain were significantly up-regulated. KEGG metabolic pathway enrichment analysis showed that the precursor of andrographolide(E, E, E)-geranylgeranyl diphosphate(GGPP)synthesis pathway(Mevalonate,MVA pathway and 2-Cmethyl-D-erythritol-4-phosphate, MEP pathway)SDE genes were significantly enriched. According to the results of RNAseq and real-time quantitative PCR(qRT-PCR),the expression of four synthase genes in the MVA pathway,HMGS (CXN00016849),HMGR(CXN00000058),MVK(CXN00002900)and MVD(CXN00004398),as well as GGPP synthesis key enzyme FPS were significantly up-regulated. In the MEP pathway,only the expression of DXS (CXN00013302)was significantly down-regulated. The type of alternative splicing(AS)that commonly occurs in the genes of the two pathways was exon skipping(SE). The protein interaction prediction showed that there were interactions between the differentially expressed genes(DEGs)of the two pathways,and the interaction networks between HMGS and CYP71 family members,and the ones among FPS1,UGT71,UGT73 and UGT76 were enriched.【Conclusion】UV-C irradiation regulates important life processes of A. paniculata. The relative expression of gene transcripts in secondary metabolism,oxidative phosphorylation,photosynthesis and other pathways show UV-C-specific response pattern. The expressions of cytoplasmic MVA pathway genes are significantly up-regulated. It is speculated that the main site of UV-Cinduced andrographolide synthesis is the cytoplasm. A. paniculata MVA pathway genes, CYP71,UGT71,UGT73 and UGT76 can be used as candidate molecular targets for andrographolide synthesis pathway research.