Introduction: Sweet potato is an important staple food crop in the world and contains abundant secondary metabolites in its underground tuberous roots. The large accumulation of several categories of secondary metabolites result in colorful pigmentation of the roots. Anthocyanin, is a typical flavonoid compound present in purple sweet potatoes and it contributes to the antioxidant activity.Methods: In this study, we developed joint omics research via by combing the transcriptomic and metabolomic analysis to explore the molecular mechanisms underlying the anthocyanin biosynthesis in purple sweet potato. Four experimental materials with different pigmentation phenotypes, 1143-1 (white root flesh), HS (orange root flesh), Dianziganshu No.88 (DZ88, purple root flesh), and Dianziganshu No.54 (DZ54, dark purple root flesh) were comparably studied.Results and discussion: We identified 38 differentially accumulated pigment metabolites and 1214 differentially expressed genes from a total of 418 metabolites and 50893 genes detected. There were 14 kinds of anthocyanin detected in DZ88 and DZ54, with glycosylated cyanidin and peonidin as the major components. The significantly enhanced expression levels of multiple structural genes involved in the central anthocyanin metabolic network, such as chalcone isomerase (CHI), flavanone 3-hydroxylase (F3H), dihydroflavonol 4-reductase (DFR), anthocyanidin synthase/leucocyanidin oxygenase (ANS), and glutathione S-transferase (GST) were manifested to be the primary reason why the purple sweet potatoes had a much higher accumulation of anthocyanin. Moreover, the competition or redistribution of the intermediate substrates (i.e. dihydrokaempferol and dihydroquercetin) between the downstream production of anthocyanin products and the flavonoid derivatization (i.e. quercetin and kaempferol) under the regulation of the flavonol synthesis (FLS) gene, might play a crucial role in the metabolite flux repartitioning, which further led to the discrepant pigmentary performances in the purple and non-purple materials. Furthermore, the substantial production of chlorogenic acid, another prominent high-value antioxidant, in DZ88 and DZ54 seemed to be an interrelated but independent pathway differentiated from the anthocyanin biosynthesis. Collectively, these data from the transcriptomic and metabolomic analysis of four kinds of sweet potatoes provide insight to understand the molecular mechanisms of the coloring mechanism in purple sweet potatoes.

The mechanism of potato (Solanum tuberosum L.) thermotolerance has been the focus of intensive research for many years because plant growth and tuber yield are highly sensitive to heat stress. However, the linkage between the aerial and belowground parts of potato plants in response to high temperatures is not clear. To disentangle this issue, the aerial and belowground parts of the heat-resistant cultivar Dian187 (D187) and the heat-sensitive cultivar Qingshu 9 (Qs9) were independently exposed to high-temperature (30 °C) conditions using a special incubator. The results indicated that when the belowground plant parts were maintained at a normal temperature, the growth of the aerial plant parts was maintained even when independently exposed to heat stress. In contrast, the treatment that independently exposed the belowground plant parts to heat stress promoted premature senescence in the plant’s leaves, even when the aerial plant parts were maintained at a normal temperature. When the aerial part of the plant was independently treated with heat stress, tuberization belowground was not delayed, and tuberization suppression was not as severe as when the belowground plant parts independently underwent heat stress. Heat stress on the belowground plant parts alone had virtually no damaging effects on the leaf photosynthetic system but caused distinct tuber deformation, secondary growth, and the loss of tuber skin colour. Transcriptome analysis revealed that the treatment of the belowground plant parts at 30 °C induced 3361 differentially expressed genes in the Qs9 cultivar’s expanding tubers, while the D187 cultivar had only 10,148 differentially expressed genes. Conversely, when only the aerial plant parts were treated at 30 °C, there were just 807 DEGs (differentially expressed genes) in the D187 cultivar’s expanding tubers compared with 6563 DEGs in the Qs9 cultivar, indicating that the two cultivars with different heat sensitivities have distinct regulatory mechanisms of tuberization when exposed to heat stress. The information provided in this study may be useful for further exploring the genes associated with high-temperature resistance in potato cultivars.

The quality of the flavor of potatoes is a crucial determinant in the commercial success of a potato variety. Plant nutrition promotes the synthesis of amino acids, and the application of exogenous amino acids has the potential to enhance the flavor quality of potatoes. In this experiment, Dian Shu 1418 and Dian Shu 23 were used as the materials, and different amino acid foliar spray trials were designed. The free amino acid content in potato tubers is determined based on high-performance liquid chromatography, and volatile tuber flavor compounds are detected using gas chromatography–mass spectrometry. The results showed that the amino acid foliar spray effectively increased the content of glycine, methionine, and phenylalanine in the tubers, subsequently increasing the levels of 2,3-dimethyl-pyrazine and 2-ethyl-3-methyl-pyrazine, enhancing the roasted fragrance characteristics of the potatoes. The experimental results provide a reference for cultivating flavor enhancement in potato tubers.

In this study, it is aimed to investigate the antioxidant mechanism of new extracts from potatoes. Four pigments, namely, Petunin, Paeonin, Malvidin and Pelargonidin, were extracted from potatoes by high performance liquid chromatography (HPLC). Our results showed that the cellular morphology and cell viability were significantly altered in gastric mucosal epithelial cells (GES-1) treated with different hydrogen peroxide (H₂O₂) concentrations over time (P < 0.05). Paeonin presented the strongest anti-oxidative effects on H₂O₂-treated cells, in both a dose- and time-dependent manner, determined by ARE-luciferase activity and HO-1 mRNA expression. After pre-treatment with Paeonin in H₂O₂-exposed cells, Keap1, Nrf2, HO-1 and NQO1 protein expressions were remarkably up-regulated. Furthermore, immunostaining of Nrf2 expression was obviously elevated in the H₂O₂ + Paeonin group over time. The GSH content in the H₂O₂ + Paeonin group was notably lower than that in the H₂O₂ + Paeonin + GSK690693 group. Paeonin promoted cell cycle with augmented Cyclin D1 and p27 protein expressions. Moreover, Paeonin suppressed apoptosis with increased Bcl2, total Caspase3 and total Caspase8 protein expressions and decreased Bax, p-Caspase3 and p-Caspase8 protein expression in H₂O₂-treated cells. These results suggested that Paeonin might exert an anti-oxidative role by activating Nrf2 signaling pathway with the changes of cell cycle and apoptosis.

Growing potatoes (Solanum tuberosum) using the idle rice fields in Southern China and the Indo-Gangetic Plains of India in the winter season through the rice–potato rotation (RC) system could support future food security. However, the modulation capacity of the RC system on soilborne fungal pathogens is still unclear. In the current study, a pot experiment was designed and conducted to monitor the dynamics of soil fungal community composition between the potato monoculture (CC) system and the RC system, where the two systems were set with the same soil conditions: autoclaving with fertilization; autoclaving without fertilization; autoclave-free with fertilization; and autoclave-free without fertilization. Then, the uncultivated soil (CK) and root-zone soil samples of conditions under the two systems were collected, and then soil physiochemical properties and enzymatic activities were determined. Next, the high-variable region (V5–V7) of fungal 18S rRNA genes of the samples were amplified and sequenced through the PCR technique and the Illumina Miseq platform, respectively. Finally, the fungal species diversity and composition, as well as the relative abundance of fungal pathogens annotated against the Fungiuld database in soil samples, were also investigated. The results showed that the RC could significantly (p < 0.05) increase soil fungal species diversity and decrease the relative abundance of soil fungal pathogens, where the RC could suppress 23 soil fungal pathogens through cultivating the rice during the summer season and 93.75% of the remaining pathogens through winter-season cultivation. Seven-eighths of the conditions under RC have lower pathogenic MGIDI indices (6.38 to 7.82) than those of the CC (7.62 to 9.63). Notably, both rice cultivation and winter planting reduced the abundance of the pathogenic strain ASV24 under the Colletotrichum genus. The bipartite fungal network between the pathogens and the non-pathogens showed that the pathogenic members could be restricted through co-occurring with the non-pathogenic species and planting crops in the winter season. Finally, the redundancy analysis (RDA) indicated that soil pH, electronic conductivity, available phosphorus content, and various enzyme activities (cellulase, urease, sucrase, acid phosphatase, catalase, polyphenol oxidase) could be the indicators of soil fungal pathogens. This experiment demonstrated that the rice–potato rotation system outperformed the potato monoculture on suppressing soilborne fungal pathogenic community.

Sweet potatoes (Ipomoea batatas) are one of the important tuberous root crops cultivated worldwide, and thier storage roots are rich in antioxidants, such as anthocyanins. R2R3-MYB is a large gene family involved in various biological processes, including anthocyanin biosynthesis. However, few reports about the R2R3-MYB gene family of sweet potatoes have been released to date. In the present study, a total of 695 typical R2R3-MYB genes were identified in six Ipomoea species, including 131 R2R3-MYB genes in sweet potatoes. A maximum likelihood phylogenetic analysis divided these genes into 36 clades, referring to the classification of 126 R2R3-MYB proteins of Arabidopsis. Clade C25(S12) has no members in six Ipomoea species, whereas four clades (i.e., clade C21, C26, C30, and C36), including 102 members, had no members in Arabidopsis, and they were identified as Ipomoea-specific clades. The identified R2R3-MYB genes were unevenly distributed on all chromosomes in six Ipomoea species genomes, and the collinearity analysis among hexaploid I. batatas and another five diploid Ipomoea species suggested that the sweet potato genome might have undergone a larger chromosome rearrangement during the evolution process. Further analyses of gene duplication events showed that whole-genome duplication, transposed duplication, and dispersed duplication events were the primary forces driving the R2R3-MYB gene family expansion of Ipomoea plants, and these duplicated genes experienced strong purifying selection because of their Ka/Ks ratio, which is less than 1. Additionally, the genomic sequence length of 131 IbR2R3-MYBs varied from 923 bp to ~12.9 kb with a mean of ~2.6 kb, and most of them had more than three exons. The Motif 1, 2, 3, and 4 formed typical R2 and R3 domains and were identified in all IbR2R3-MYB proteins. Finally, based on multiple RNA-seq datasets, two IbR2R3-MYB genes (IbMYB1/g17138.t1 and IbMYB113/g17108.t1) were relatively highly expressed in pigmented leaves and tuberous root flesh and skin, respectively; thus, they were identified to regulate tissue-specific anthocyanin accumulation in sweet potato. This study provides a basis for the evolution and function of the R2R3-MYB gene family in sweet potatoes and five other Ipomoea species.