Leafy sweet potato is a new type of sweet potato, whose leaves and stems are used as green vegetables. However, sweet potato tips can be affected by pre-harvest factors, especially the intensity of light. At present, intercropping, greenhouse planting, and photovoltaic agriculture have become common planting modes for sweet potato. Likewise, they can also cause insufficient light conditions or even low light stress. This research aimed to evaluate the influence of four different shading levels (no shading, 30%, 50%, and 70% shading degree) on the growth profile of sweet potato leaves. The net photosynthetic rate, chlorophyll pigments, carbohydrates, and polyphenol components were determined. Our findings displayed that shading reduced the content of the soluble sugar, starch, and sucrose of leaves, as well as the yield and Pn. The concentrations of Chl a, Chl b, and total Chl were increased and the Chl a/b ratio was decreased for the more efficient interception and absorption of light under shading conditions. In addition, 30% and 50% shading increased the total phenolic, total flavonoids, and chlorogenic acid. Transcriptome analysis indicated that genes related to the antioxidant, secondary metabolism of phenols and flavonoids, photosynthesis, and MAPK signaling pathway were altered in response to shading stresses. We concluded that 30% shading induced a high expression of antioxidant genes, while genes related to the secondary metabolism of phenols and flavonoids were upregulated by 50% shading. And the MAPK signaling pathway was modulated under 70% shading, and most stress-related genes were downregulated. Moreover, the genes involved in photosynthesis, such as chloroplast development, introns splicing, and Chlorophyll synthesis, were upregulated as shading levels increased. This research provides a new theoretical basis for understanding the tolerance and adaptation mechanism of leafy sweet potato in low light environments.

MYB transcription factors (TFs) play vital roles in plant growth, development, and response to adversity. Although the MYB gene family has been studied in many plant species, there is still little known about the function of R2R3 MYB TFs in sweet potato in response to abiotic stresses. In this study, an R2R3 MYB gene, IbMYB330 was isolated from sweet potato (Ipomoea batatas). IbMYB330 was ectopically expressed in tobacco and the functional characterization was performed by overexpression in transgenic plants. The IbMYB330 protein has a 268 amino acid sequence and contains two highly conserved MYB domains. The molecular weight and isoelectric point of IbMYB330 are 29.24 kD and 9.12, respectively. The expression of IbMYB330 in sweet potato is tissue-specific, and levels in the root were significantly higher than that in the leaf and stem. It showed that the expression of IbMYB330 was strongly induced by PEG-6000, NaCl, and H₂O₂. Ectopic expression of IbMYB330 led to increased transcript levels of stress-related genes such as SOD, POD, APX, and P5CS. Moreover, compared to the wild-type (WT), transgenic tobacco overexpression of IbMYB330 enhanced the tolerance to drought and salt stress treatment as CAT activity, POD activity, proline content, and protein content in transgenic tobacco had increased, while MDA content had decreased. Taken together, our study demonstrated that IbMYB330 plays a role in enhancing the resistance of sweet potato to stresses. These findings lay the groundwork for future research on the R2R3-MYB genes of sweet potato and indicates that IbMYB330 may be a candidate gene for improving abiotic stress tolerance in crops.

The sweet potato weevil (Cylas formicarius) is an important pest in the growing and storage of sweet potatoes. It is a common pest in the sweet potato production areas of southern China, causing serious harm to the development of the sweet potato industry. For the existing cultivars in China and abroad, there is no sweet potato variety with complete resistance to the sweet potato weevil. Thus, understanding the regulation mechanisms of sweet potato weevil resistance is the prerequisite for cultivating sweet potato varieties that are resistant to the sweet potato weevil. However, very little progress has been made in this field. In this study, we inoculated adult sweet potato weevils into sweet potato tubers. The infected sweet potato tubers were collected at 0, 24, 48, and 72 h. Then, a miRNA library was constructed for Eshu 6 and Guang 87 sweet potato tubers infected for different lengths of time. A total of 407 known miRNAs and 298 novel miRNAs were identified. A total of 174 differentially expressed miRNAs were screened out from the known miRNAs, and 247 differentially expressed miRNAs were screened out from the new miRNAs. Moreover, the targets of the differentially expressed miRNAs were predicted and their network was further investigated through GO analysis and KEGG analysis using our previous transcriptome data. More importantly, we screened 15 miRNAs and their target genes for qRT-PCR verification to confirm the reliability of the high-throughput sequencing data, which indicated that these miRNAs were detected and most of the expression results were consistent with the sequencing results. These results provide theoretical and data-based resources for the identification of miRNAs in response to sweet potato weevil infection and an analysis of the molecular regulatory mechanisms involved in insect resistance.

Background: Sweet potato (Ipomoea batatas (L.) Lam.) is widely cultivated as an important food crop. However, the molecular regulatory mechanisms affecting root tuber development are not well understood. Methods: The aim of this study was to systematically reveal the regulatory network of sweet potato root enlargement through transcriptomic and metabolomic analysis in different early stages of sweet potato root development, combined with phenotypic and anatomical observations. Results: Using RNA-seq, we found that the differential genes of the S1 vs. S2, S3 vs. S4, and S4 vs. S5 comparison groups were enriched in the phenylpropane biosynthesis pathway during five developmental stages and identified 67 differentially expressed transcription factors, including AP2, NAC, bHLH, MYB, and C2H2 families. Based on the metabolome, K-means cluster analysis showed that lipids, organic acids, organic oxides, and other substances accumulated differentially in different growth stages. Transcriptome, metabolome, and prophetypic data indicate that the S3-S4 stage is the key stage of root development of sweet potato. Weighted gene co-expression network analysis (WGCNA) showed that transcriptome differential genes were mainly enriched in fructose and mannose metabolism, pentose phosphate, selenium compound metabolism, glycolysis/gluconogenesis, carbon metabolism, and other pathways. The metabolites of different metabolites are mainly concentrated in amino sugar and nucleotide sugar metabolism, flavonoid biosynthesis, alkaloid biosynthesis, pantothenic acid, and coenzyme A biosynthesis. Based on WGCNA analysis of gene-metabolite correlation, 44 differential genes and 31 differential metabolites with high correlation were identified. Conclusions: This study revealed key gene and metabolite changes in early development of sweet potato root tuber and pointed out potential regulatory networks, providing new insights into sweet potato root tuber development and valuable reference for future genetic improvement.

Sweet potato is a hexaploid heterozygote with a complex genetic background, self-pollination infertility, and cross incompatibility, which makes genetic linkage analysis quite difficult. Genome-wide association studies (GWAS) provide a new strategy for gene mapping and cloning in sweet potato. Storage root flesh color (SRFC) is an important sensory evaluation, which correlates with storage root flesh composition, such as starch, anthocyanin, and carotenoid. We performed GWAS using SRFC data of 300 accessions and 567,828 single nucleotide polymorphism (SNP) markers. Furthermore, we analyzed transcriptome data of different SRFC varieties, and conducted real-time quantitative PCR (qRT-PCR) to measure the expression level of the candidate gene in purple and non-purple fleshed sweet potato genotypes. The results showed that five unique SNPs were significantly (−log₁₀P > 7) associated with SRFC. Based on these trait-associated SNPs, four candidate genes, g55964 (IbF3′H), g17506 (IbBAG2-like), g25206 (IbUGT-73D1-like), and g58377 (IbVQ25-isoform X2) were identified. Expression profiles derived from transcriptome data and qRT-PCR analyses showed that the expression of g55964 in purple-fleshed sweet potato was significantly (p < 0.01) higher than that of non-purple fleshed sweet potato. By combining the GWAS, transcriptomic analysis and qRT-PCR, we inferred that g55964 is the key gene related to purple formation of storage root in sweet potato. Our results lay the foundation for accelerating sweet potato genetic improvement of anthocyanin through marker-assisted selection.

Chalcone isomerase (CHI) is not only an enzyme related to flavonoid biosynthesis, but also one of the key enzymes in the flavonoid metabolic pathway. In this study, members of the CHI gene family were identified in the whole genome of sweet potato. Bioinformatics methods were used to analyze the physical and chemical properties, systematic evolution, conserved domain, chromosome location, cis-acting elements of the promoter, and so on, of CHI gene family members. In addition, the tissue site-specific expression of CHI gene family members and their expression patterns under three kinds of abiotic stress were analyzed. The results showed that five members of IbCHI gene family were identified in sweet potato, which were unevenly distributed on four chromosomes. The protein secondary structure and tertiary structure were consistent, and there was a conservative domain related to chalcone isomerase. The prediction of subcellular localization showed that it was mainly located in cytoplasm and chloroplast. Systematic evolution showed that the members of sweet potato CHI gene family could be divided into Type I-IV, and the Type I gene IbCHI1 showed CHI catalytic activity in transgenic callus. The collinearity gene pairs were identified between sweet potato and allied species. Its promoter contains light response elements, hormone response elements, and stress response elements. The results of real-time fluorescence quantitative PCR (qRT-PCR) analysis showed that the expression of the IbCHI gene was tissue-specific and that the catalytic genes IbCHI1 and IbCHI5 serve as primary responders to abiotic stress, while the non-catalytic members IbCHI3 and IbCHI4 may fine-tune metabolic flux or participate in low-temperature, salt, and drought stress signaling. This study can provide a theoretical basis for a follow-up functional genomics study of the chalcone isomerase gene family in sweet potato.