Preliminary Study On The Mechanism Of Anthocyanin Accumulation In Foxtail Millet Leaves Based On The Transcriptome

Foxtail millet(Setaria italica(L.)P.Beauv.)is a dominant coarse cereal in Shanxi province.In recent years,with the people’s increasing demand for healthy food,the planting areas of foxtail millet have increased year by year.Anthocyanins,natural water-soluble pigments,which play an important role on plant stress resistance and benifit on human nutrition and health.Although the mechanism of anthocyanins biosynthesis has been extensively studied,the mechanism in foxtail millet is still poorly understood.In this study,purple-leaf variety B100 and green-leaf variety YG1 were used as experimental materials.In order to explore the mechanism of anthocyanin accumulation in foxtail millet,the distribution characteristics of anthocyanins in leaves were observed by microscope and the gene expression pattern in mature leaves between two varieties were compared using transcriptome sequencing analysis.The main results were as follows:1.The anthocyanins were mainly distributed in the upper and lower epidermis,trichome and adjacent mesophyll cells of foxtail millet leaves,and were higher in the upper epidermis than the lower epidermis.From seedling to maturing stage,with the deepening of purple color in leaves,anthocyanins gradually diffused into the inner layer.2.The total antioxidant capacity of foxtail millet leaves was positively correlated with the content of total anthocyanins,but not with the content of total chlorophylls and total carotenoids.The accumulation of anthocyanins was closely related to the accumulation of soluble sugar.3.There were 1184 differently expressed genes identified from the transcriptome sequencing results at leaf mature stage in two foxtail millet varieties.Compared to YG1,nine structural genes(PAL,4CL,DFR,LDOX-1,LDOX-2,UFGT,5GT,GT,AT)and two transcriptional factors(MYB,b HLH)related to anthocyanin biosynthesis were all up-regulated in B100.4.The expression patterns of 9 structural genes and 2 transcriptional factor genes at different stages of leaf development in two millet varieties were analyzed by q RT-PCR.It was found that DFR,LDOX-2,AT,MYB and b HLH were related to anthocyanin accumulation at seedling stage,whereas PAL,4CL,DFR,LDOX-1,LDOX-2,UFGT,5GT,GT,AT,MYB and b HLH all played important roles in anthocyanin accumulation at leaf mature stage.In conclusion,anthocyanins were the key pigments causing purple leaves of foxtail millet.The genes of DFR,LDOX-2,AT,MYB and b HLH were closely related to anthocyanin accumulation in foxtail millet leaves at seedling stage,and all 9 structural genes and 2 transcriptional factor genes might be responsible accunulation of anthocyanins at mature stage.