Transcriptome analysis of Polygala tenuifolia seedlings induced by methyl jasmonate and key genes mining for triterpenoid biosynthetic pathway / 中草药

ABSTRACT

Objective: To obtain the transcriptome sequence database induced by methyl jasmonate (MeJA) and identify the genes related to the biosynthesis of triterpenoid saponin in Polygala tenuifolia. Methods: The seedlings grown for 30 d were respectively treated with sterile water, 50 μmol/L MeJA and 100 μmol/L MeJA for 24 h. The transcriptome data of seedlings of P. tenuifolia were obtained by Illunima HiseqTM 2000 150PE sequencing and de novo splicing of Unigene was realized by Trinity software. The GO classification, KOG functional annotation, metabolism of KEGG metabolic pathway, protein function annotation analysis, differential gene analysis and screening were completed based on BLAST. Results: A total of 52.19 Gb clean data were obtained after the transcriptome of P. tenuifolia being assembled by Trinity software, and 54 426 Unigenes were assembled with an average length of 1 604 bp. All Unigenes were annotated in the public databases NR, NT, KEGG, Swissprot, GO, and Pfam. Through differential analysis of genes responding to MeJA, a total of 3 390 differentially expressed genes (DEGs) were found, of which 1 287 were up-regulated and 2 103 were down-regulated. The response of DEGs showed that the total number and up-regulated number of P. tenuifolia seedlings treated by 100 μmol/L MeJA was the highest. KEGG enrichment analysis showed that differentially expressed genes were significantly enriched in metabolic pathways including phenylpropanoid biosynthesis, cysteine and methionine metabolism, starch and sucrose metabolism, carbon fixation in photosynthetic organisms and terpenoid backbone biosynthesis. Furthermore, a total of 59 Unigenes involved in anthraquinones biosynthesis were found according to the assignment of KEGG pathway. Expression analysis showed that AACT, HMGS, HMGR, MK, PMK, MPD, DXS, IDI, FPPS, SQS, SE and β-AS were up-regulated after being induced by MeJA. Conclusion: In this study, the transcriptome of P. tenuifolia seedlings treated with methyl jasmonate was analyzed, and candidate genes related to triterpenoid skeleton biosynthesis of P. tenuifolia were obtained. MeJA can induce the expression of genes related to triterpenoid skeleton synthesis, which provided a wealth of data resources for the molecular biology research and also laid the foundation for the analysis of the secondary metabolic pathways of triterpenoid saponins in P. tenuifolia.