| As one of the ten famous traditional flowers in China,tree peony belongs to the section Moutan in the genus Paeonia of the Paeoniaceae family,which is valuable at ornamental,medicinal and edible.Floral scent is an important ornamental character of plants,which has high physiological value and economic value.At present,the research on the floral composition of peony is still at the initial stage,mainly focusing on the detection and identification of its floral components.In this study,headspace solid phase microextraction(HS-SPME)combined with gas chromatography-mass spectrometry(GC-MS)was used to analyze the floral components of 20 tree peony varieties in their full blooming stage.Secondly,the floral emission rule of P.’Hign Noon’ with the flowering process was studied,and the transcriptome sequencing of the petals of P.’Hign Noon’ was conducted by using high-throughput sequencing technology.Finally,candidate genes related to the metabolic pathway of terpenes were selected by combining transcriptome data and floral analysis results,and their expression levels in different development stages of petals were analyzed by qRT-PCR.The main conclusions are as follows:1.20 varieties have significant differences in floral composition and released amount.P.’Fen Mian Tao Sai’ has the largest floral composition with 47 varieties,and P.’Zui Tao’has the largest floral release amount with 3314.5ng/g.Each variety has its unique components,but the content is low,which cannot affect the floral characteristics of the variety.However,the linalool in the flowers of P.’Hign Noon’,which accounts for 46.63%of the total released amount of P.’Hign noon’ flowers,is the main active component of P.’Hign Noon’ flowers.2.The release pattern of flowers in the flower development stage was first increased and then decreased,and the total released amount in the initial opening stage was the largest,while the total released amount in the first period of flower bud was the smallest,and it was dominated by aliphatic compounds,while terpenoids were dominant in the other four stages.Linalool occupied the main position of P.’Hign Noon’ since the period of colour,its content increased continuously,and reached the highest proportion in the second blooming period(63.85%).3.The cDNA libraries of 5 samples from 3 developmental stages of P.’Hign noon’petals for transcriptome sequencing were Constructed.A total of 102,869,542 clean reads were obtained,and 228,349 Unigenes and 244,933 Transcripts were obtained after splicing and assembly.A total of 19,371 differentially expressed genes were obtained through pairwise comparison,and four significantly enriched pathways associated with floral metabolism were found through KEGG enrichment analysis,including sesquiterpenoid and triterpenoid biosynthesis,monoterpenoid biosynthesis,limonene and pinene degradation,and phenylpropylene biosynthesis.4.A total of 18 candidate genes were screened from transcriptome data,which specifically expressed in terpenoid metabolic pathways.Through qRT-PCR analysis,it was found that the expression levels of Unigene287537、Unigene252388 and Unigene252470 were consistent with the floral release patterns,and the differences were quite large,so it was speculated that it regulated the synthesis and release of linalool in the flowers of P.’Hign Noon’.This study from 20 peony varieties screening get flowers specific germplasm P.’Hign Noon’,Clarify the law of floral release,Combined transcriptome analysis,exploring the synthesis and regulation of P.’Hign Noon’ floral scent from the transcriptional level,through the expression analysis of candidate genes,the key structural genes for the floral formation of P.’Hign Noon’ were obtained,which laid a foundation for elucidation of the floral synthesis and regulation mechanism of peony. |
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