| Rosa rugosa is not only one of the oldest ornamental plants in the world,but also a world-famous economic plant.Rosa rugosa essential oil extracted from rosa rugosa flowers has the reputation of "liquid gold".It is a high-end raw material for making expensive cosmetics and is deeply loved by consumers.However,the oil content of rosa rugosa flowers is low,only about three ten thousandths.How to improve the yield and quality of rose essential oil has always been the focus of many scientific researchers.In addition,the current rose cultivation management is relatively extensive,and drought and other adversity stresses are often encountered during the cultivation process.To study the effects of drought stress on rose fragrance and essential oil components,and to find ways to alleviate rose drought stress and to clarify its mechanism,which is useful for guiding rosa rugosa production.Significance.In this paper,the method of exogenous spraying of methyl jasmonate was used to study its effect on the drought resistance and floral fragrance synthesis of rosa rugosa.Combined with transcriptome sequencing,the gene expression profile of rosa rugosa flowers treated with exogenous methyl jasmonate was established and screened by jasmine.The differential genes significantly induced by methyl acid methyl ester and the functions of related differential genes were further verified in petunia,laying the foundation for efficient rosa rugosa cultivation,essential oil production and variety breeding.The main research results are as follows:First,the 0.5mmol/L methyl jasmonate solution was used to spray "Purple Roses" under drought stress to study the effect of exogenous methyl jasmonate treatment on alleviating the drought stress of rosa rugosa.Morphological observation revealed that under drought stress,the growth of rose plants treated with methyl jasmonate was significantly better than that of untreated plants.The leaf water content,total chlorophyll content,malondialdehyde content,superoxide dismutase activity,catalase activity and total protein content and other related physiological indicators were tested,and it was found that compared with untreated control plants,spraying the leaf water content,total chlorophyll content,superoxide dismutase activity,catalase activity and total protein content of rosa rugosa containing methyl jasmonate increased,while the content of malondialdehyde decreased,indicating that exogenous jasmonic acid Methyl ester treatment can effectively alleviate the damage to purple roses by drought stress.Second,using ’Fenghua Roses’ as the test material,GC-MS detection combined with transcription sequencing was used to further study the effect of exogenous spraying of methyl jasmonate on rosa rugosa fragrance components and the expression of genes related to floral fragrance synthesis.The results showed that exogenous methyl jasmonate Ester treatment can obviously promote the release of rosa rugosa fragrance and increase the content of main floral fragrance components.Transcriptome data analysis showed that a total of 766 differentially expressed genes were detected,of which 615 genes were up-regulated and 151 genes were down-regulated.Combined with the unique domains of the terpene synthase gene family,a hidden Markov model was constructed,and finally two terpene synthase genes,RrAFS1 and RrAFS2,were screened out,which may respond to the synthesis of rosa rugosa fragrance treated with methyl jasmonate.Third,using ’Fenghua Roses’ as the test material,the full-length sequences of RrAFSl and RrAFS2 genes were cloned.The ORF of the RrAFS1 gene sequence is 1743 bp in length,encoding a total of 580 amino acids.The ORF of the RrAFS2 gene sequence is 558 bp in length,encoding a total of 186 amino acids.Taking the bud stage as a reference,the expression of RrAFSl and RrAFS2 genes in different developmental stages of rosa rugosa were detected.The results showed that their expression patterns were similar,and the expression level gradually increased as the rosa rugosa flowers opened,and the expression level reached the maximum during the blooming period;The decay of flowers and the gradual decline in expression levels are consistent with the trend of changes in the content of the main floral components of rosa rugosa,further indicating that RrAFS1 and RrAFS2 may be closely related to the synthesis of vosa rugosa fragrance components.Forth,the overexpression vector of RrAFS1 and RrAFS2 gene was constructed,and the RrAFS2 gene were successfuly introduced into the model plant Petunia for functional verification.After the plants were fully grown,the phenotypic changes of the plants were observed.It was found that the flowers of the petunia transgenic with the RrAFS2 gene were slightly larger than those of the wild-type plants,and the receptacles of the transgenic plants were also fuller.The headspace solid-phase microextraction combined with GC-MS was used to determine the floral components and content of wild-type and transgenic petunia flowers in bloom.The results showed that compared with wild-type plants,the main floral components of RrAFS2 transgenic petunia plants were the same Significantly increased,among which the content of benzyl benzoate changed most obviously,8.5 times more than that of wild-type plants.Therefore,the RrAFS2 gene can significantly promote the release of petunia aroma,and can be used as an important genetic resource for subsequent use of genetic engineering to increase the content of rosa rugosa essential oil. |
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