Transcriptome analysis of Samsoniella hepialiinduced by salicylic acid and crucial genes digging for metabolic pathways of cordycepic acid

Abstract:

[Objective]Cordycepic acid is one of the most important active substances in Samsoniella hepiali,but the low content greatly restricts its industrial application.Salicylic acid (SA) is an abiotic inducer,and we found that it could increase the content of cordycepic acid in S.hepiali.However,the metabolic pathways of cordycepic acid and its response to SA are not clear.This study was designed to obtain the transcriptome information of S.hepiali in response to SA treatment,and to explore key enzyme genes for the metabolic pathways of cordycepic acid.[Methods] In this study,SA was used to induce S.hepiali,and after 8 h treatment,high-throughput transcriptome sequencing was performed on induced and uninduced mycelia.[Results] A total of 40.37 Gb clean data was acquired,and 20 317 unigenes with an average length of 1 357.13 bp were constructed.Additionally,13 592 unigenes were annotated in the public databases NR,NT,KEGG,Swissprot,GO,and Pfam,and 2 574 differentially expressed genes were identified,in which 1 135 were up-regulated and 1 439 were down-regulated.KEGG enrichment analysis demonstrated that the differentially expressed genes were concentrated in the pathways such as cell cycle,meiosis,galactose metabolism,DNA replication,glycolipid biosynthesis,and glyceride metabolism.Furthermore,13 unigenes involved in metabolic pathways of cordycepic acid were found based on the assignment of KEGG pathway.The expression of genes glk,gpi,gla,mpi,fbp and mtld related to cordycepic acid biosynthesis was all up-regulated after the induction of SA,yet that of the gene mdh involved in cordycepic acid consumption was down-regulated,and the qRT-PCR results were in substantial agreement with RNA-Seq data.[Conclusion] Transcriptome information of S.hepiali induced by SA was obtained,and candidate genes for the metabolic pathways of cordycepic acid were identified.SA improved the expression of the biosynthetic genes and inhibited the gene transcription related to cordycepsic acid consumption,thus increasing the accumulation of cordycepic acid.This study provides reference for regulating the genes related to the biosynthetic pathways of cordycepic acid in S.hepiali by SA,and also facilitates the investigation on the regulatory mechanism of cordycepic acid metabolism.