Associative Transcriptomics Of Anthocyanin Content In Tuberous Roots And Preliminary Analysis Of MYB Gene Family In Sweet Potato

Sweet potato [Ipomoea batatas(L.)Lam.] is one of the most important crops in China,and it is also regarded as the most healthy vegetable by WHO.However,sweet potato is a self-incompatible hexaploid plant,and its genetic composition is complex.So far,its whole genome has not yet been assembled which is lagging behind the development of molecular genetics and functional genomics of sweetpotato compared with other major crops.Up to date,the molecular regulation mechanism of many agronomic traits in sweet potato is still unclear.Associative transcriptomics is a new method for identification of candidate genes of target traits,especially suitable for the complex species without reference genome,which has been successfully applied in oak,rape and other species.MYB gene family is one of the largest gene families in plants,and it is a kind of important transcription factors in organism.MYB transcription factor can mediate the growth and development of plants,maintain the primary and secondary metabolism of plants,and improve the stress tolerance of plants by regulating the expression of genes.A large number of MYB gene family members have been identified in many species whose genome have been sequenced,such as Arabidopsis,maize,and grape,and the biological function of some genes have been elucidated.In this study,the genetic basis for the regulation of anthocyanin content in sweetpotato roots was studied in the first time by using associative transcriptomics method,and the sweet potato MYB gene family was preliminary analyzed based on the transcriptome database.Our work mainly includes the following four aspects:Firstly,we analyzed the anthocyanin content in root tuber of 77 sweet potato cultivars(including 41 non purple and 36 purple sweet potato).And then,through transcriptome sequencing and associative transcriptomics analysis,a large number of transcripts which are significantly associated with anthocyanin content in tuberous roots were identified.And these significantly associated transcripts were further analyzed by KEGG enrichment analysis and gene coexpression network analysis,preliminarily revealing the complex genetic network for regulating the anthocyanin content in sweet potato.Secondly,by comparative biology analysis,we identified some important genes which involved in the molecular pathways of anthocyanin accumulation in sweet potato,including transcription factors,anthocyanin synthesis structural genes and anthocyanin transporters.And the molecular pathway of anthocyanin accumulation in sweet potato was constructed,and the key genes were further verified.The results of this study reveal that the genetic networks regulating the anthocyanin content of sweet potato are highly conservative compared with other species.Thirdly,since MYB transcription factors play an important role in anthocyanin accumulation,we further analyzed the MYB gene family in sweet potato.Through the analysis of multiple transcriptome database,we identified 145 members of MYB gene family.By analyzing the protein domain and phylogenetic relationship of these family members,they can be classified into 4 subfamilies: 81 members in R2R3,4 in R1R2R3,2 in 4R and 58 members in MYB-related subfamily.Finally,to further investigate the functional diversification of sweet potato R2R3 MYB gene family,we analyzed the phylogenetic relationship between sweet potato and Arabidopsis,explored the expression level of MYB genes in 77 sweet potato varieties as well as in different tissues of two sweet potato strains.The results revealed that the different expression patterns of R2R3 MYB genes occurred in different strains and tissues of sweet potato,which implied their functions have been diversified after gene duplication.Overall,through the associative transcriptomics analysis,our study systematically identified a series of genes associated with anthocyanin accumulation and preliminary revealed its molecular regulation network,which provided us with an important candidate gene for further study on molecular mechanism of anthocyanin accumulation in sweet potato.In addition,through the analysis of MYB gene family members’ functional diversification based on the transcriptome database,will provide us with a basic data for the further study of the biological function of this important transcription factors gene family in sweet potato.