| Ipomoea batatas(L),the main food crop in the world,plays an important role in national food and feed security.Sweet potato was planted during Ming Dynasty in China.At present,the yield and planting area of sweet potato in China are the first in the world,but its yield is vulnerable to various biotic and abiotic stress.Sweet potato is edriched in various nutrients.Purple-fleshed sweet potato is popular because it is riched in anthocyanins.Anthocyanins are edible pigments with high nutritional value.However,the research mechanism of anthocyanins in sweet potato tuberous root is not clear.Weighted gene co-expression network analysis(WGCNA)is a systematic biological method,which can be used to identify co-expressed modules,explore the relationship between gene modules and related traits and screen hub genes in the network.Based on the published the genomic of sweet potato,combined with the transcriptomics of sweet potato tuberous roots with different flesh colors and sweet potato transcriptomics under different salt stress,the anthocyanin related coexpression network and salt tolerance related co-expression network of sweet potato were constructed respectively.One co-expression module and 47 anthocyanin related genes of sweet potato were mined and verified by q RT-PCR,six salt tolerant co-expression modules and 20 genes of sweet potato were mined.IbWRKY72,a salt tolerant gene,was cloned and the expression pattern under salt stress was analyzed.The main results of this study were as follows:1)Through transcriptional sequencing of purple-fleshed sweet potato variety XZS-3 and white-fleshed sweet potato variety XS-18,a total of 3,647 differential genes were obtained by differential gene analysis.Among them,1,810 genes were up-regulated in XZS-3 and 1,837 genes were up-regulated in XS-18.2)Based on the WGCNA analysis of 92 transcriptomics from purple and non purple-fleshed sweet potato,we constructed a co-xpression network related with anthocyanins biosysthsis.A total of 28 gene co-expression modules were identified,in which four modules were purple sweetpotato specific.flavonoid biosynthesis process and anthocyanin containing metabolic process by GO analysis,and mined 47 hub genes related to anthocyanins.The expression of seven hub genes was verified by q RT-PCR.3)Based on the WGCNA analysis of 12 transcriptomics sweet potato salt stress to construct the co expression network,identified 6 coexpression modules related with salt stress in sweet potato.Furthermore,20 hub genes related to salt tolerance were identified from four characteristic modules which were significantly positively correlated with salt stress.GO analysis showed that the four specific modules could be enriched into transmembrane transport,salicylic acid stimulated cell response,abiotic response,and hypertonic response.4)The IbWRKY72 was successfully cloned.The CDS of IbWRKY72 gene was 1,518 bp.Bioinformatics analysis shows that IbWRKY72 encoded 505 amino acids with a molecular weight of54,273.32 k Da and contained a complete WRKY domain.Its subcellular localization was predicted to be on nuclear.Phylogentic analysis showed that IbWRKY72 was closely related to Ipomoea nil and Ipomoea trifida.The expression of IbWRKY72 in root was the highest,which indicated that it played an important role in root.The expression of IbWRKY72 was up-regulated under salt stress.To sum up,this study explored the gene modules and core genes related with anthocyanin and salt tolerance in sweet potato.The results will provide candidate genes for improving salt tolerant and anthocyanin in sweet potato cultivars. |
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