| Sect.Chrysantha Chang,belonging to Theaceae family and Camellia genus,the flower color of species in Sect.Chrysantha Chang with a series of complete yellow tones.However,the regulation mechanism of the color depth difference of petals in Sect.Chrysantha Chang remains unclear.In our study,the blooming petals of C.chuongtsoensis(CZ),C.achrysantha(ZD)and C.parvipetala(XB)were used as study materials.The flower color phenotype and total pigment content were determined,and the petal epidermal cell was observed for scientifically identifying the flower color differences.The effects of physical and chemical factors on pigment were studied in vitro.The metabolome and transcriptome analysis were used to identify the main color substances and dig the key regulatory genes.The purpose of this study was to find out the molecular regulation mechanism of the metabolism difference of three research materials,which laid the foundation for further analysis of the golden flower color formation mechanism of Sect.Chrysantha Chang,and also provided reference suggestions for molecular breeding of yellow Camellia.The main research results are as follows:(1)The yellowness of petals of three research materials varied significantly,and the yellowness of C.chuongtsoensis(CZ)was the highest,C.achrysantha(ZD)was the second,C.pavipeiala(XB)was the lowest.The carotenoid content of the three materials accounted for a very small proportion in the petals of Sect.Chrysantha Chang,and flavonoid metabolites were the key pigment group that determine the difference of flower color.(2)Physicochemical factors(temperature,light and metal ions)had important effects on camellia pigments.The low temperature(4℃)and light protection conditions were conducive to maintain the flower pigment stability,while high temperature(60℃)and long-term ultraviolet conditions(>6 h)will destroy the structure of anthocyanin and lead to the increase of light absorption value.The degradation of anthocyanin was accelerated by sunlight and natural light.Fe3+ and Al3+ formed highly pigmented complexes with anthocyanin substances,resulting in color enhancement.(3)The chalcone,flavone and flavonol metabolites affected the yellowness of petals.Based on the UPLC-ESI-MS\MS technique,356 kinds of flavonoid metabolites were detected,and 36 DAFs were enriched in upper flavonoid metabolism pathways,among which 10 key metabolites were identified to be closely related to deepening petal yellowing.They included 6 chalcones(myricetin,quercetin,quercetin-3-O-rhamnoside,quercetin-3-O-sophoroside,quercetin-3-O-sambubioside,quercetin-3-O-rutinoside),2 flavones(luteolin-7-O-neohesperidoside and apigenin-7-O-glucoside),and 2 flavonols(phloretin-2’-O-glucoside and naringenin chalcone).(4)Structural genes(CHI,CYP75B1,FLS,DFR and LAR)and transcription factors(MYB and EREBP)were involved in flower color regulation.Based on the RNA sequencing technology,a total of 154185 Unigenes were obtained from research materials,and 37 DEGs located in flavonoid metabolism pathway were obtained,among which 8 key structural genes were identified involved in the regulation of key metabolite synthesis.They included 1 CHI,I CYP75B1,1 FLS,3 DFR and 2 LAR genes.We believed that the up-regulation of CHI and FLS promoted the synthesis of flavones and flavonols,thus deepening the yellowness of petals.However,the up-regulation of DFR and LAR genes led to the synthesis of excessive colorless flavanols,thereby weakening the petals’ yellowness.In addition,we identified 5 TFs of the MYB and EREBP families that regulated the expression of key structural genes,and auxin signal transduction and transporter related genes might be involved in petal pigments synthesis and accumulation,thus affecting flower color presentation. |
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