Analysis of Flavonoid in Waterlily(Nymphaea colorata)Flower Petals and Identification of Key Genes for Flower Color Formation
In order to determine the flavonoid content,components and key genes in the flavonoid metabol-ic pathway of waterlily(Nymphaea colorata)petals at different developmental stages,high performance liquid chromatography(HPLC)and ultra-performance liquid chromatography-tandem quadrupolar time of flight high resolution mass spectrometry(UPLC-Triple-TOF-MS/MS)were used to analyze the content of anthocyanin and flavonol glycosides in the petals of N.colorata in five developmental stages(S1-S5).The results showed that the difference on flavonoid content between blue and white petals was obvious.The content of anthocyanin and flavonol glycosides in white petals remained at a low level,especially in S4 and S5 stages,while the flavonoids of blue petals were significantly higher than that of white.This may be the cause of white and blue color of petal.Three anthocyanins and 11 flavonol glycosides were identified from the petals of N.colorata.The flavonoid compositions of blue petals and white petals were the same.The three anthocyanins were delphinidin 3-O-β-galactopyranoside,delphinidin 3-O-(2″-O-galloyl-6″-O-acetyl-β-galactopyranoside,and delphinidin 3'-O-(2″-O-galloyl-6″-O-acetyl-β-galactopyranoside.The flavonol gly-cosides mainly included quercetin 3-O-galactoside,myricetin 3-O-α-L-(3″-O-malonyl)-rhamnopyranoside,myricetin 3-O-α-L-rhamnopyranoside,myricetin 3-O-α-L-(3″-O-acetyl)-rhamnopyranoside,and quercetin 3-O-α-L-(3″-O-malonyl)-rhamnopyranoside.Besides,Real-Time quantitative PCR(RT-qPCR)was used to further analyze the expression of genes related to flavonoid biosynthetic pathway.We found that during the five developmental stages of blue flower petals,the genes's transcriptional expression patterns of fla-vonoid 3'5'-hydroxylase(F3'5'H),flavonol synthetase(FLS)and dihydroflavonol 4-reductase(DFR)were consistent with the trend of anthocyanin accumulation,indicating that these genes might be responsi-ble for anthocyanin accumulation in blue petals.Moreover,the expression levels of F3'5'H and glycosyl-transferase gene(GT)in blue flowers were much higher than those in white flowers,suggesting that F3'5'H and GT play the roles in the color difference between blue and white flowers in N.colorata.This study provides new evidence for further understanding the molecular mechanism of color formation of N.colorata flower,and lays a foundation for molecular breeding of blue color flower in waterlily.