The Study On The Synthesis Mechanism Of Flower Color To Purple Rhododendron Latoucheae Franch Based On Multi-omics Analysis

Rhododendron latoucheae Franch is a valuable plant in China,with strong landscape application prospects.The common Rhododendron latoucheae is white-pink with light flowers.The purple color is a special variation of the Rhododendron latoucheae and has great ornamental value.What are the key metabolites responsible for the difference in flower color between the white-pink and purple Rhododendron latoucheae?Which genes are involved in the regulation of flower color in purple Rhododendron latoucheae?What kind of regulatory relationship between metabolites and genes?The exploration of these issues can provide a theoretical basis for the cultivation of Rhododendron latoucheae with higher ornamental value and promote the application of Rhododendron latoucheae in landscape.In this study,Rhododendron latoucheae were observed,white-pink and purple Rhododendron latoucheae with significant differences in flower color were selected through plant phenology observation.The white-pink Rhododendron latoucheae was used as the control and the purple Rhododendron latoucheae as the research object.Four developmental periods of flowering process were selected and divided into eight groups,each group has three biological replicates,twenty-four samples were selected for it determination of analysis petal chromogenic substance content,transcriptomic and metabolomic analysis of biological information and qRT-PCR.Using UPLC-MS/MS and Denovo-RNAseq technology,we completed the qualitative and quantitative detection of metabolites and the construction of cDNA libraries.The differential metabolites associated with the flower color of purple Rhododendron latoucheae were gradually identified by differential analysis,trend analysis and key metabolite correlation analysis.Next,the key differential genes associated with the flower color formation of purple Rhododendron latoucheae were identified by differential gene expression analysis,KEGG and GO enrichment analysis,GSEA analysis,and WGCNA analysis.The key metabolites found in multi-omics were combined with the key genes by association analysis to find out the regulation of metabolites by genes.Finally,the gene expression was verified by qRT-PCR experiments.The results are as follows:(1)A total of 1 057 metabolites were detected,of which 285 were flavonoid metabolites.The differential metabolites were significantly enriched in the flavonoid metabolic pathway.(2)The trends of anthocyanin content in Rhododendron latoucheae were the same as those of flower color,and there were 10 anthocyanins that differed significantly in whitepink and purple Rhododendron latoucheae.The contents of peonidin-3-O-glucoside,dihydromyricetin,malvidin-3-O-galactosideand gallocatechin were significantly correlated with the flower color of Rhododendron latoucheae.There was substrate competition between gallocatechin and malvidin-3-O-galactoside.(3)106.09 Gb of high-quality reads were obtained,57 761 Unigenes were assembled,and 11 019 differential genes were identified.Structural genes such as RlHST,RlFAOMT,RlCHS,RlCHI,RlCYP75A,RlLDOX,RlLAR,RlANR,RlF3H and RlFLS were associated with flower color.RlF3GT1 is the structural gene that has the greatest effect on the flower color of Rhododendron latoucheae.(4)RlLAR and RlANR are higher in white-pink Rhododendron latoucheae,forming more colorless gallocatechin,epicatechin and epigallocatechin,leading to its lighter flower color.RlF3GT1 content is higher in purple Rhododendron latoucheae,which enables the synthesis of more peonidin-3-O-glucoside,malvidin-3-O-galactoside.RlF3GT1,RlLAR and RlANR are the key structural genes affecting the flower color of Rhododendron latoucheae.(5)RlbHLH130,RlbHLH41,RlbHLH123 and RIMYB4 were significantly correlated with the contents of anthocyanins and flavonoids.The contents of Peonidin-3-O-glucoside,Malvidin-3-O-galactoside were positively correlated with the expression of RlbHLH130 and RlbHLH41,and negatively correlated with the expression of RlbHLH123 and RlMYB4.There was a strong correlation between the expression of transcription factor RlMYB4 and the structural gene RILAR.In summary,it is speculated that peonidin-3-O-glucoside,malvidin-3-O-galactoside are the key anthocyanins affecting the flower color of Rhododendron latoucheae.RlF3GT1,RlLAR and RlANR are the key structural genes affecting the flower color of purple Rhododendron latoucheae,and RlbHLH130,RlbHLH41,RlbHLH123 and RlMYB4 are the key transcription factors affecting the flower color of purple Rhododendron latoucheae.The increased expression of RlF3GT1 and decreased expression of RlLAR and RlANR can lead to the synthesis of peonidin-3-O-glucoside,malvidin-3-O-galactoside,which is the key reason for the purple color of Rhododendron latoucheae.RlMYB4 is correlated with the expression of RlLAR,which can affect the flower color by affecting the synthesis of anthocyanin in Rhododendron latoucheae.