| The flower of tea tree is the reproductive organ of tea plant.The flower organ structure is complex and has strong genetic stability,which is less affected by environment.Tea flower has the same biochemical components as tea leaves.Compared with tea leaves,tea flowers are richer in flavonoids and saponins,and contain theanine,which is not contained in flower of other species.Therefore,tea flower has good antioxidant,hypoglycemic,anti-tumor and other biological activities.The flowers of tea tree are generally white,with a small amount of green and pink.Flower color is an agronomic character of plant with important physiological significance.The study of metabolite composition and flower color formation mechanism of different flower colors is of great significance for plant color breeding and flower product development,and also provides theoretical basis for subsequent tea tree variety classification.In the earlier stage,it was found that some tea flowers of Babu tea in Wangmo County were pink in color.At present,there is a lack of research on the formation mechanism of pink tea flower.Therefore,in this paper,we measured the epidermal cells,color values and main biochemical components of different flower colors of Babu tea in full bloom.The anthocyanin metabolites of flower petals of different flower colors of Babu tea were determined by ultra high liquid chromatography-tandem mass spectrometry(UPLC-MS/MS).Metabolic differences and key differential genes were analyzed by combining transcriptome sequencing technology.The mechanism of the formation of pink flower color of Palbu tea was analyzed by combining anthocyanin metabolites and transcriptome analysis.The main results obtained are as follows:(1)Taking Babu tea flower as material,the skin structure of Palbu tea tree flower was analyzed,and the color,p H value,total flavonoid content,anthocyanin,chlorophyll and carotenoid content of tea tree flower petals were determined,and the relationship between them and the formation of flower color of tea tree was analyzed.It was found that there were some differences in the structure of epidermal cells in Palbu tea.Epidermal cells mainly included ovoid,regular flat and convex cells.The average value of L* value(color brightness value)is 79.46,the average value of a* value(color red and green bias value)is 6.89,the average value of b* value(color yellow and blue bias value)is 11.78,the average value of H value is-0.25,the average value of h value(hue Angle)is 0.66,and the average value of C value(chroma value)is 15.06.Brightness L* value,color Angle value H value,red and green degree value a* value increased with the deepening of pink color;The p H of petal cell fluid was between 5.52 and 5.82,all of which were acidic.The flower color did not change significantly due to the changes of flavonoids,chlorophyll and carotene,but the contents of flavonoids,chlorophyll and carotene of P5 material were the highest.With the increase of anthocyanin content,the pink color was higher.a* was positively correlated with anthocyanin content,and L* was positively correlated with p H.The increase of anthocyanin,carotenoid and flavonoid content promoted the increase of flower redness of Palbuu tea,and anthocyanin was the main reason.(2)By means of UPLC/MS-MS(Ultra-high performance liquid chromatography-mass spectrum in series),three different colors of tea flower of Babu tea was used to qualitatively and quantitatively analyze anthocyanin metabolites.A total of 64 anthocyanin metabolites were detected,including 52 anthocyanin metabolites,4 proanthocyanidins and 8 flavonoids metabolites.There were 9 different anthocyanin metabolites in different materials.With the color difference of the three tea tree flowers,the total number of differential metabolites in the inner and outer layers was different.The inner petals were significantly higher than the outer petals,and the up-regulated differential metabolites in the outer petals gradually increased,while the up-regulated differential metabolites in the inner petals were not significantly different.Anthocyanin metabolites in the inner and external of three tea tree flowers of different colors annotated the flavonoid metabolic pathway and anthocyanin metabolic pathway respectively,among which the metabolites of cyanidin-3-O-glucoside,cyanidin-3-O-rutinoside-5-O-glucoside,pelargonidin-3-O-glucoside,dihydromyricetin,dihydrokaempferol were significantly up-regulate.The high content of cyanidin-3-O-glucoside,cyanidin-3-O-rutinoside,pelargonidin-3-O-glucoside in the samples may be the main reason for the formation of pink color.(3)Illumina sequencing method was used to excavate the key color regulatory genes from the flower petals of three different tea trees of Palbu tea.A total of 357201730 raw reads were obtained by sequencing.Eleven differential genes related to flavonoid synthesis and anthocyanin synthesis were identified based on GO enrichment,including 4 CHI genes,2 CHS genes,2 DFR genes,2 UDP genes and 1 LODX gene.WPE vs WE,PE vs WE,PE vs WPE,WPI vs WI,PI vs WI,PI vs WPI,37,48,37,39 transcription factors were differentially expressed,respectively.The most abundant transcription factors include ERF,b HLH,MYB,WRKY,etc.Correlation analysis between differential genes and main chromic metabolites sagittarin 3-O-glucoside,sagittarin3-O-rutin and geranin-3-o-glucoside showed that,CSS0000672,CSS0020068,CSS0010687 and CSS0030597 were strongly correlated with anthocyanin substances,which were important candidate genes,and also speculated to be the key genes affecting the formation of Palbucha pink tea flower.In conclusion,different cell morphology,weak acid environment and anthocyanin content in petals provided favorable conditions for the formation of the pink color of tea tree flowers.The synthesis of sagittarin 3-O-glucoside,sagittarin 3-O-rutin and geranin-3-o-glucoside in pink tea tree flowers was more.At the same time,the high expression levels of genes CSS0000672,CSS0020068,CSS0010687 and CSS0030597 were highly positively correlated with the contents of anthocyanin substances such as centaurin-3-O-glucoside and centaurin-3-(6-O-P-caffeoyl)-glucoside.Is the main reason for the pink color of tea plant flowers. |
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