Cloning and expression analysis of ApbHLH80 gene in Andrographis paniculata

Objective: To clone the transcription factor gene ApbHLH80 of Andrographis paniculata (A. paniculata) and analyze its bioinformatics and expression. Methods: Primers were designed according to the transcriptome database of A. paniculata, and the full-length sequence of ApbHLH80 was cloned by PCR amplification and other methods. The physical and chemical nature of the protein encoded by this gene was analyzed and predicted through bioinformatics online tools. Reverse transcription-quantitative PCR (RT-qPCR) was used to analyze the expression pattern of this gene under methyl jasmonate treatment. And the content of andrographolide was determined by high- performance liquid chromatography (HPLC). Results: Bioinformatics analysis showed that the open reading frame length of the gene contained 1,095 bp and encoded 364 amino acids. The amino acid sequence encoded by this gene without signal peptide and transmembrane structure had a molecular weight of approximately 39.96 ku and a theoretical isoelectric point of 5.73, and it’s a hydrophilic protein in the nucleus. This protein was closely related to many species, such as Perilla frutescens var. Frutescens, Salvia miltiorrhiza, Salvia splendens and Salvia hispanica, all of which had the bHLH_AtbHLH_like conserved domain. The results of RTqPCR analysis showed that the gene expression of ApbHLH80 was the highest in leaves, and its expression pattern was closely related to andrographolide synthesis in response to the induction of methyl jasmonate. Conclusion: The successful cloning of ApbHLH80 gene may regulate the andrographolide synthesis, providing theoretical support for further exploration of its potential regulatory effects.