| Sweet potato（Ipomoea batatas（L.）Lam.）is an important food crop in the world,especially since its rich variety of nutrients in the storage roots,it is widely loved by the people.The purple-fleshed sweet potato has accumulated rich anthocyanin,which makes the color of the storage roots turn purple,making the purple-fleshed sweet potato receive more extensive attention.Anthocyanins have always been a hot topic for many scholars.Anthocyanin is one of the important characters of ecology and quality of sweet potato.Not only because it can accumulate various pigments for plants and provide certain stress resistance,but also because it can provide some resistance to coercion.Aside from this,it can make a very important contribution to human health.Anthocyanin belongs to the secondary metabolite of sweet potato,and is one of the flavonoid compounds,which is accumulated with large amount in the storage root of sweet potato.Although the metabolic regulation of anthocyanin has been well studied in model plants,it is still poorly understood in sweet potato.Especially in the context of the existence of many sweet potato varieties,it is still not possible to use molecular biological techniques to explain biodiversity between purple-fleshed sweet potatoes and other sweet potatoes at the molecular ecological level.Moreover,most of the researches on anthocyanin in sweet potato are focused on the key enzyme genes of its synthesis pathway,but there are few studies on its regulation.In order to further deepen the research on sweet potato anthocyanin,we used the publicly available sequencing data of 104 sweet potato germplasm resources first.The regulation network of anthocyanin in sweet potato storage roots was constructed by combining e QTL and co-expression strategy,and the association analysis was also conducted on the flesh color of sweet potato storage roots,revealing the genetic basis of anthocyanin accumulation in purple-fleshed sweet potato storage roots.Then the regulatory network was verified by the molecular biology methods to clarify its molecular mechanism.Finally,the regulation model of anthocyanin accumulation in storage root of purple-fleshed sweet potato was put forward to explain the color variation diversity of sweet potato storage roots at molecular level.The results as follow:1.Construction of regulatory network of anthocyanin synthesis in sweet potato.By homologous alignment and manual annotation,a total of 172 genes related to flavonoid biosynthesis were identified in I.trifida genome.A total of 148 genes were found to be expressed in storage roots from 88 published transcriptome data.e QTL analysis showed that 18 e QTL were responsible for the expression variation of 39 genes,one of which was co-localized with the QTL locus for flesh color of sweet potato storage roots.The regulation network of anthocyanin biosynthesis in sweet potato storage roots was constructed by combining e QTL and co-expression methods,which included a significant regulator Ib MYB1-2 and its 17 downstream target genes.In the end,these genes were used as bait genes to identify 63 co-expressed genes,which were predicted to be involved in the biosynthesis of anthocyanin in storage roots.2.Association analysis of storage root flesh color of sweet potato.A total of 104sweet potato accessions were used to conduct association analysis for storage root flesh color.The results showed that a QTL locus associated with storage root flesh color was co-localized with one of the e QTLs identified above.e QTL analysis showed that the expression of Ib MYB1-2 gene was regulated by cis-e QTL,suggesting that the variation of its promoter might be the main reason for the change of sweet potato flesh color.Furthermore,PAV（presence/absence variation）markers were developed to detect the promoter variation of Ib MYB1-2 in the associated populations,and its polymorphisms were integrated into the SNP genotype dataset to perform e QTL and GWAS analysis again.The results showed that PAV of Ib MYB1-2 promoter was significantly associated with the variation of Ib MYB1-2 expression and the storage root flesh color.At the same time,225cultivars of sweet potatos（94 cultivars of purple-fleshed sweet potatos and 131 other cultivars of sweet potatos）were screened with this marker,and the final results also showed that the variation of Ib MYB1-2 was significantly correlated with sweet potato flesh color(P-value=2.06×10-53).3.Rapid verification of the function of Ib MYB1-2 with the aid of genetic transformation mediated by Agrobacterium rhizogenes.The results showed that the overexpressed roots of Ib MYB1-2 showed obvious purple phenomenon and accumulated more anthocyanin.The transcriptome and q PCR experiments showed that the genes related to anthocyanin synthesis,such as the transcription factor Ibb HLH42 and structural genes,were highly expressed in the transgenic trichome.These results indicated that the Ib MYB1-2 gene played an important role in the regulation of anthocyanin synthesis in sweet potato.4.Regulation model of anthocyanin accumulation in storage roots of purple-fleshed sweet potato.In order to further verify the interactions between Ib MYB1-2 and the key genes of sweet potato anthocyanin synthesis,yeast single hybridization and LUC transient expression experiments were used.The results showed that Ib MYB1-2 could directly activate the expression of Ib C4H,Ib CHS,Ib CHI,Ib F3H,Ib DFR,Ib ANS,Ib UFGT,Ib GST,Ib UGT,Ib ACC1,and Ibb HLL42.In addition,Ibb HLH42 can strengthen the transcriptional activation activity of Ib MYB1-2.Based on the above evidence,we proposed a regulatory model for the accumulation of anthocyanin in the storage root of purple-fleshed sweet potato:the variation of Ib MYB1-2 is the main reason for the change of the flesh color of sweet potato,which can directly activate the expression of the genes related to the synthesis of anthocyanin in sweet potato,and the up-regulated expression of Ibb HLH42 can also enhance the activation activity of Ib MYB1-2. |
PDF Full Text Request