| Tree Peony(Paeonia suffruticosa Andr.)belongs to the section Moutan in the genus Paeonia of Paeoniaceae family.It is an important ornamental plant in China and occupies an important position in garden application and flower culture.There are many varieties of peonies.Current research mainly focuses on flower color,flower pattern and flowering stage regulation,while that of flower fragrance is less.In this study,‘High Noon’ was used as the experimental material.Based on headspace solid phase microextraction(SPME)and gas chromatography-mass spectrometry(GC-MS),changes of petal floral composition were determined and analysized at different flowering stages.At the same time,the transcriptome sequencing technology was used to identify and screen the key genes in the synthesis pathway of terpenoids,which laid a foundation for the analysis of the terpenes biosynthesis of peony flowers.1.The floral fragrance composition of different organs of ‘High Noon’ in full opening stage was obviously different.The volatiles of petals and stamens were mainly monoterpenoids and sesquiterpenoids,and linalool was the main component.The volatiles of pistils were mainly 3-hexene-1-ol and hexanol,and the relative contents of terpenoids were significantly lower than those of petals and stamens.3-Hexen-1-ol,acetate was the main volatile component in leaves.A total of 36 compounds,including 29 terpenoids,were detected in the petals at four flowering stages of ‘High Noon’.With the flowering process,relative content of monoterpenoids increased gradually,while relative content of sesquiterpenoids decreased gradually.Sesquiterpenoids were the main volatiles in ballon stage,and the relative content of germacrene D was 34.68%.The monoterpenoids and sesquiterpenoids increased rapidly in the initial opening stage,the relative content of linalool was 21.70%,and the germacrene D was 24.05%.The relative content of linalool gradually increased to 42.74% and53.82% in half opening and full opening period,and germacrene D decreased to 14.26% and10.84%.2.Transcriptome sequencing was performed of ‘High Noon’ in ballon stage and full opening stage,in petals and stamens respectilvly.A total of 23695 DEGs were identified by differential analysis,142 of which were related to terpene metabolism.KEGG enrichment analysis was performed on the identified DEGs.1-Deoxy-d-xylose-5-phosphate synthase(DXS),1-deoxy-d-xylose-5-phosphate reductisomerase(DXR),acetyl-Co A acetyltransferase(AACT),geranyl diphosphate synthase(GPPS)and terpene synthase(TPS)may be the main regulatory genes of terpene synthesis of ‘High Noon’.Related genes were screened and verified by q RT-PCR.It was speculated that Cluster-6583.39785,Cluster-6583.56227 may be involved in the biosynthesis of linalool in ‘High Noon’.3.According to transcriptome sequencing data,a Ps GPPS gene was cloned.The full CDS length of this structural gene was 1266 bp,encoded 421 amino acids.Bioinformatics analysis,multiple sequence alignment and phylogenetic tree construction showed that GPPS protein was highly conserved.Subcellular localization indicated that the protein derived from Ps GPPS gene was localized in chloroplasts.Injection of Ps GPPS overexpression vector into tomato fruits by transient expression,increased the GPPS enzyme protein activity in tomato fruit,which were 2.0 times and 2.2 times of wild type and control,respectively.It was speculated that Ps GPPS gene may regulate the expression of GPPS protein.In conclusion,monoterpenoids and sesquiterpenoids were the main floral compounds in peony ‘High Noon’.With the flowering process,the relative content of monoterpenoids increased gradually,while the sesquiterpenoids relative content decreased gradually.DXS,DXR,AACT,GPPS and TPS genes may regulate the synthesis of terpenoids.One Ps GPPS gene was cloned.Agrobacterium tumetobacter mediated transient expression suggested that Ps GPPS gene might regulated the expression of GPPS enzyme protein. |
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