Identification And Preliminary Analysis Of BHLH Gene Family In Sweet Potato

Sweet potato(Ipomoea batatas(L.)Lam.)is the seventh most important crop in the world and the fourth most significant in China.And it is also one of the most promising cash crops for its rich in nutrients and high industrial value.However,sweet potato is a hexaploid plant and its genome is complex,so far there is no reliable reference genome,which has hindered the study of molecular genetic and functional genomics of sweet potato.Compared with other major crops,the molecular regulation mechanism of many agronomic traits of sweet potato is still unrevealed.bHLH(basic helix-loop-helix)gene family is ubiquitous in plants and animals,and it is the second largest gene family of plants.bHLH transcription factors play a key role in the process of plant growth and development,as well as in response to abiotic stress.Meanwhile,it is also involved in various substances synthesis and signal transduction in higer plant.Although a large number of bHLH transcription factors has been identified in many species whose genome have been sequenced,and the function of some of the genes has been studied,but the biological function of most of the bHLH transcription factors has not been elucidated.In this study,a large number of bHLH transcription factors were identified based on the transcriptome database,and the diversification of these genes was explored by gene expression profile and phylogenetic analysis.And we focused on the synthesis of bHLH transcription factors associated with anthocyanin synthesis.The main work of this study includes the following aspects:Firstly,bioinformatics analysis was performed in multiple transcriptome databases,and 152 non-redundant sweet potato bHLH gene family members were identified.By analyzing the protein domain,motif composition and phylogenetic relationship of these family members,they an be divided into 18 subfamilies.Secondly,in order to predict the biological function of sweet potato bHLH genes,we analyzed the phylogenetic relationship of bHLH genes in sweet potato and Arabidopsis thaliana to identify the putative orthologs.The results could help us speculate the biological function of bHLH gene family in sweet potato.Thirdly,to further investigate the functional diversification of the sweet potato bHLH gene family,this study use the mature tuberous roots of 77 sweet potato varieties and as well as in the different tissues of two sweet potato strains as experimental materials to transcriptome Sequencing.Finally,as a case study,we performed association analysis between the expression of bHLH genes and the anthocyanin content of tuberous roots in 77 sweet potato varieties.The results of association analysis showed that IbbHLH2 was significantly associated with anthocyanin content in the roots of sweet potato(R2=0.5;P=1.64E-14).And this most associated gene was verified by real-time quantitative PCR,suggesting that the IbbHLH2 gene may play a key role in the process of anthocyanin synthesis in tuberous roots of sweet potato.Overall,this study has laid an important foundation for the further investigation of the biological function of sweet potato bHLH genes,and provides a candidate gene for the study of molecular mechanisms involved in the synthesis of anthocyanin in sweet potato.