Molecuar Mechanism Of The Formation Of Fruit Pigment In Jujube Fruits

Chinese jujube(Ziziphus jujuba Mill.)is indigenous to China and belongs to the Rhamnaceae.Its red pigment is a natural pigment,resulting higher phenolic substances and nutritional value.While,its composition and molecular regulatory mechanisms remain unclear.In this study,we selected two jujube cultivars ‘Junzao' and the color mutant ‘Tailihong' fruit skin as experimental materials,and investigated the types of anthocyanin,biosynthesis,transport and transcriptional regulation of anthocyanin in Jujube which based on the ‘Junzao' genome,metabolite profiling and transcriptome database.The main findings are as follows:1.During jujube fruit development,the chlorophylls play an important role in determining the fruit's green color in the initial stages in ‘Junzao',while,anthocyanin is the primary pigment in ‘Tailihong' which has little correlation with carotenoids,and the red color of jujube fruit at maturity is due to a blend of various amounts of lutein and possibly some trace amounts of anthocyanins.Furthermore,13 anthocyanins,116 flavonoids(flavonols,flavanones and isoflavones)and 42 phenylpropanes were identified by metabolite profiling.In addition,two key genes(ZjANS,ZjUGT79B1)and eight transcript factors(ZjMYB113?ZjMYB5?ZjGL3a?ZjGL3b?ZjTT8?ZjWDR1?ZjWDR2 and ZjWDR3)were screened in jujube fruit skin.2.The main anthocyanin component in 'Tailihong' jujube skin is peonidin 3,5-Odiglucoside and cyanidin 3-O rutinoside,following by cyanidin.During the development of jujube fruit,the content of anthocyanin has a high correlation with the expression patterns of ZjANS and ZjUGT79B1.Transient overexpression of ZjANS and ZjUGT79B1 can significantly increase the anthocyanin content of the fruit.In vitro enzyme activity assay showed that recombinant ZjANS could catalyze proanthocyanin to cyanidin,and the recombinant ZjUGT79B1 recognized UDP-galactose was used as the sugar donor.The peonidin 3,5-O-diglucoside is the highest content of anthocyanin in jujube,so that,a methylated gene ZjCCoAOMT was been screened,which can catalyze cyanidin 3,5-O glucoside to form 3,5-O glucoside.3.Based on the metabolome transcriptome database,eight candidate transcription factors(ZjMYB113,ZjMYB5,ZjGL3 a,ZjGL3b,ZjTT8,ZjWDR1,ZjWDR2 and ZjWDR3)were obtained.According to the expression analysis of different tissues and different developmental stages,ZjMYB5,ZjTT8 and ZjWDR3 were found,which were highly consistent with anthocyanin accumulation.Subcellular localization results showed that ZjMYB5 and ZjTT8 were localized in the nucleus,while ZjWDR3 was localized not only in the nucleus but also in the cytoplasm.The dual luciferase results showed that the transcription factor ZjMYB5 could activate the transcriptional activities of the ZjANS and ZjUGT79B1 promoters.The synergistic expression of ZjMYB5 and ZjTT8 significantly enhanced the activation of ZjANS and ZjUGT79B1 promoters.Further addition of the ZjWDR3 transcription factor can make the enhancement effect more apparent.The GUS reporter gene transient transformation assay was consistent with the results of dual luciferase.