Abstract
BackgroundSweet potato (Ipomoea batatas (L.) Lam.) is a highly heterozygous autohexaploid crop with high yield and high anthocyanin content. Purple sweet potato is the main source of anthocyanins, and the mechanism of anthocyanin biosynthesis in storage roots has not been fully revealed.ResultsIn order to reveal the mechanism of anthocyanin biosynthesis and identify new homologous genes involved in anthocyanin biosynthesis in the storage roots of sweet potato, we used Ningzishu 1 and Jizishu 2 as parents to construct a F1 hybrid population. Seven anthocyanin-containing lines and three anthocyanin-free lines were selected for full-length and second-generation transcriptome analyses. A total of 598,375 circular consensus sequencing reads were identified from full-length transcriptome sequencing. After analysis and correction of second-generation transcriptome data, 41,356 transcripts and 18,176 unigenes were obtained. Through a comparative analysis between anthocyanin-containing and anthocyanin-free groups 2329 unigenes were found to be significantly differentially expressed, of which 1235 were significantly up-regulated and 1094 were significantly down-regulated. GO enrichment analysis showed that the differentially expressed unigenes were significantly enriched in molecular function and biological process. KEGG enrichment analysis showed that the up-regulated unigenes were significantly enriched in the flavonoid biosynthesis and phenylpropanoid biosynthesis pathways, and the down-regulated unigenes were significantly enriched in the plant hormone signal transduction pathway. Weighted gene co-expression network analysis of differentially expressed unigenes revealed that anthocyanin biosynthesis genes were co-expressed with transcription factors such as MYB, bHLH and WRKY at the transcription level.ConclusionsOur study will shed light on the regulatory mechanism of anthocyanin biosynthesis in sweet potato storage roots at the transcriptome level.
Highlights
Sweet potato (Ipomoea batatas (L.) Lam.) is a highly heterozygous autohexaploid crop with high yield and high anthocyanin content
A total of 95.64% of the unigenes were annotated by alignment with at least one database, which provided a basis for subsequent analysis of differentially expressed genes
Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis found that the up-regulated unigenes were significantly enriched in the flavonoid biosynthesis (46 unigenes), phenylpropanoid biosynthesis pathways (33 unigenes), and glutathione metabolism (31 unigenes) (Fig. 3), and the down-regulated unigenes were significantly enriched in the plant hormone signal transduction pathway (24 unigenes) (Additional file 7: Figure S6)
Summary
Sweet potato (Ipomoea batatas (L.) Lam.) is a highly heterozygous autohexaploid crop with high yield and high anthocyanin content. Purple sweet potato is the main source of anthocyanins, and the mechanism of anthocyanin biosynthesis in storage roots has not been fully revealed. Sweet potato is a highly heterozygous hexaploid and an important food crop, which has been grown around the world with an area of 9.2 million hectares (FAO, 2017). Sweet potato has the characteristics of high yield, barren tolerance and wide applicability [1]. Anthocyanins are the products of the secondary metabolic pathway of plant flavonoids and have been applied as natural watersoluble pigments [2]. Anthocyanins in purple sweet potato have high light and thermal stabilities [4], which make it an excellent raw material for extracting anthocyanins
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