基于转录组测序的苦瓜皂苷合成相关基因的鉴定和分析OA北大核心CSTPCD

[Objective]As the main source of bitterness in bitter gourd fruit,saponin possesses various medicinal values including hypoglycemic and anticancer properties.This paper aimed at identifying the metabolic pathways and genes involved in the regulation of bitter gourd saponin biosynthesis,so as to provide the theoretical basis for further analysis of the molecular mechanism of bitter gourd saponin formation.[Method]Using the bitter gourd high-generation inbred line GK24 as the test material,fruit tissues were sampled at the ovary stage(T1),young fruit stage(T2),commodity fruit stage(T3),and maturity fruit stage(T4).The saponin content of bitter gourd at different periods were determined by the vanillin-glacial acetic acid method,and the differentially expressed genes(DEGs)were identified using the method of transcriptome sequencing.[Result]From T1 to T4,the endogenous saponin content of bitter gourd showed significant decrease with fruit development.A total of 17 504 genes were identified by transcriptome sequencing,and the number of down-regulated genes was higher than that of up-regulated genes in the comparison of the three groups of T1-vs-T2,T2-vs-T3,and T3-vs-T4.GO enrichment analysis showed that phosphorus-containing complex metabolic process,kinesin complex and 2-succinyl-6-hydroxy-cyclohexadiene-1-carboxylic acid synthetase activity were the most significantly enriched terms in biological process,cellular component and molecular function,respectively.KEGG analysis showed that global and overview mapping,carbohydrate metabolism,and amino acid metabolism were the most significantly enriched pathways in all three comparative groups.The genes could be categorized into 20 profiles based on their expression patterns.Genes in profile 0 gradually decreased from T1 to T4,showing similar pattern of saponin content changes with bitter gourd fruit development.14 genes related to bitter gourd saponin biosynthesis were identified from profile 0,including AAT1,HMG1,MVK,PMK,MVD2,and FPS1 in the terpene skeleton biosynthesis pathway,SS12,SQE1,and CPQ in the sesquiterpene and triterpene biosynthesis pathway,and the postmodifying enzyme genes CYP97A3,CYP71AN24,UGT94E5 and UGT73C6.The results of RNA-seq were validated by qRT-PCR method.[Conclusion]The saponin content of bitter gourd decreased with the fruit development.Bitter gourd saponin was synthesized through the terpenoid bone biosynthesis(ko00900)metabolic pathway to accumulate terpenoid saponin skeleton in the first,and then produce saponins through the sesquiterpene and triterpene biosynthesis(ko00909)metabolic pathway and the modification of oxidoreductase and glycosyltransferase successively.A total of 14 genes related to the saponin biosynthesis of bitter gourd have been identified in the present study.