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Sweetpotato (Ipomoea batatas (L.) Lam.) is a globally significant storage root crop, but it is highly susceptible to yield reduction under severe drought conditions. Therefore, understanding the mechanism of sweetpotato resistance to drought stress is helpful for the creation of outstanding germplasm and the selection of varieties with strong drought resistance. In this study, we conducted a comprehensive analysis of the phenotypic and physiological traits of 17 sweetpotato breeding lines and 10 varieties under drought stress through a 48 h treatment in a Hoagland culture medium containing 20% PEG6000. The results showed that the relative water content (RWC) and vine-tip fresh-weight reduction (VTFWR) in XS161819 were 1.17 and 1.14 times higher than those for the recognized drought-resistant variety Chaoshu 1. We conducted RNA-seq analysis and weighted gene co-expression network analysis (WGCNA) on two genotypes, XS161819 and 18-12-3, which exhibited significant differences in drought resistance. The transcriptome analysis revealed that the hormone signaling pathway may play a crucial role in determining the drought resistance in sweetpotato. By applying WGCNA, we identified twenty-two differential expression modules, and the midnight blue module showed a strong positive correlation with drought resistance characteristics. Moreover, twenty candidate Hub genes were identified, including g47370 (AFP2), g14296 (CDKF), and g60091 (SPBC2A9), which are potentially involved in the regulation of drought resistance in sweetpotato. These findings provide important insights into the molecular mechanisms underlying drought resistance in sweetpotato and offer valuable genetic resources for the development of drought-resistant sweetpotato varieties in the future. [ABSTRACT FROM AUTHOR]

Sweetpotato (Ipomoea batatas (L.) Lam.), which has a complex genome, is one of the most important storage root crops in the world. Sweetpotato blades are considered as a potential source of natural antioxidants owing to their high phenolic content with powerful free radical scavenging ability. The molecular mechanism of phenolic metabolism in sweetpotato blades has been seldom reported thus far. In this work, 23 sweetpotato genotypes were used for the analysis of their antioxidant activity, total polyphenol content (TPC) and total flavonoid content (TFC). 'Shangshu19' and 'Wan1314-6' were used for RNA-seq. The results showed that antioxidant activity, TPC and TFC of 23 genotypes had significant difference. There was a significant positive correlation between TPC, TFC and antioxidant activity. The RNA-seq analysis results of two genotypes, 'Shangshu19' and 'Wan1314-6', which had significant differences in antioxidant activity, TPC and TFC, showed that there were 7810 differentially expressed genes (DEGs) between the two genotypes. Phenylpropanoid biosynthesis was the main differential pathway, and upregulated genes were mainly annotated to chlorogenic acid, flavonoid and lignin biosynthesis pathways. Our results establish a theoretical and practical basis for sweetpotato breeding with antioxidant activity and phenolics in the blades and provide a theoretical basis for the study of phenolic metabolism engineering in sweetpotato blade. [ABSTRACT FROM AUTHOR]

• Peroxidases produce o -quinones and form black or brown deleterious pigments. • Structure and catalytic sites of peroxidase from 'Zhongshu 1′ sweet potato were resolved. • Ascorbic acid, sodium metabisulfite, glutathione inhibited browning of sweet potato. • Mechanism and type between peroxidase and inhibitors were revealed by molecular docking. Browning is an obstacle in industrial development of sweet potato. Peroxidase from sweet potato cv. 'Zhongshu 1′ was purified and analyzed by chromatography and mass spectrometry. Peroxidase from 'Zhongshu 1′ sweet potato was a monomeric protein with 37.2 kDa. A binding site of peroxidase to guaiacol was discovered using molecular docking, with Arg61 and Ala191 being near the active region important for guaiacol catalysis. The IC 50 values of ascorbic acid, sodium metabisulfite and glutathione were (1.97 ± 0.03)×10−4, (2.99 ± 0.07)×10−4 and (6.87 ± 0.12)×10-3 mol L-1, respectively. These compounds were competitive (ascorbic acid, (1.96 ± 0.03) ×10−4 mol L-1), non-competitive (sodium metabisulfite, (1.08 ± 0.03) ×10−4 mol L-1) and uncompetitive inhibitors (glutathione, (10.78 ± 0.05)×10-3 mol L-1) of peroxidase. Fluorescence spectrum showed the static quenching type of three inhibitors. The change of residues near the active site in peroxidase contributed to prevention of browning. [ABSTRACT FROM AUTHOR]

Sweetpotato blades are rich in the functional secondary metabolite chlorogenic acid (CGA), which deepen potential for effective utilization of the blade in industry. In this study, we evaluated the type and content of CGA in the blades of 16 sweetpotato genotypes and analyzed the correlation between CGA content and antioxidant capacity. Then we isolated and characterized IbGLK1 , a GARP-type transcription factor, by comparative transcriptome analysis. A subcellular localization assay indicated that IbGLK1 is located in the nucleus. Overexpression and silencing of IbGLK1 in sweetpotato blade resulted in a 0.90-fold increase and 1.84-fold decrease, respectively, in CGA content compared to the control. Yeast one-hybrid and dual-luciferase assays showed that IbGLK1 binds and activates the promoters of IbHCT , IbHQT , IbC4H , and IbUGCT , resulting in the promotion of CGA biosynthesis. In conclusion, our study provides insights into a high-quality gene for the regulation of CGA metabolism and germplasm resources for breeding sweetpotato. • Chlorogenic acid content varies significantly among genotypes of sweetpotato. • Characterization of key transcription factor IbGLK1 in chlorogenic acid metabolism. • IbGLK1 promotes chlorogenic acid biosynthesis in sweetpotato. • IbGLK1 directly activates transcription of chlorogenic acid metabolism genes. [ABSTRACT FROM AUTHOR]

We report here a new cultivation system for sweetpotato [ Ipomoea batatas (L.) Lam.] production, named grafted overhead-sweetpotato cultivation (GOSC) system. In this system, sweetpotato (as scions) was grafted with convolvulaceae relatives (as stocks), and the stems of grafted sweetpotato were buried in a solid medium without any nutrient and hung in the air to regenerate overhead-sweetpotato (storage roots). The results showed that Ipomoea trifida (6×), Beinong5521 (5×) and SH-2 (6×) were the best stocks. All the tested sweetpotato cultivars could produce overhead-sweetpotato with different yields. The mixture of sand, perlite and vermiculite with a 1:1:1 (v/v/v) ratio was the best solid medium for the GOSC system. The key stage of overhead-sweetpotato formation was about 20 days to 55 days after stem buried. Since storage roots are not regenerated from stocks grown in fertilized soil but from scion stems buried in non-fertilized solid medium, it seemed that the grafted overhead-sweetpotato plants had root-function spatial division (RFSD), i.e. absorbing roots of stocks and storage roots of scions. The graft compatibility with sweetpotato, the stock without underground storage roots, and the stem-buried media without nutrient supply, are the key factors for RFSD and overhead-sweetpotato production. This system could be used as a model for the study of the interaction between stock and scion as well as the source-sink relationship in sweetpotato. [ABSTRACT FROM AUTHOR]

Sweetpotato [ Ipomoea batatas (L.) Lam.] storage roots tend to become brown due to damage incurred during harvest, transportation, processing and storage. Understanding the mechanism of sweetpotato browning is of great significance for breeding varieties with low browning, which have greater economic value. In this study, after analysis of the Browning Degree (BD) of 76 sweetpotato genotypes and analyzing the correlations between BD, the activities and contents of phenylalanine ammonia-lyase (PAL), peroxidase (POD) and polyphenol oxidase (PPO) for 21 genotypes, two genotypes, S07 (browning-resistant) and S28 (easily browned), were selected to elucidate the differences in the browning mechanism after fresh-cutting by physiological and transcriptome analyses. Genotype S28 had higher PAL, POD and PPO activities and a higher phenolic content after fresh-cutting compared with the basal level and genotype S07. Cell compartmentalization was severely damaged in fresh-cut S28. An RNA-Seq analysis showed that the phenylpropanoid biosynthesis in S28 was more active and gene families of related enzymes were more actively expressed. In conclusion, sweetpotato browning is due to a high content of phenolic compounds, and the high activity of PPO and POD resulting from the up-regulation of related genes. This study provided high quality breeding materials and a relevant theoretical basis for breeding browning-resistant sweetpotato varieties. [Display omitted] • Significant differences in fresh-cut browning among different sweetpotato genotypes. • S28 had higher PAL, POD, PPO enzyme activity and phenolic contents. • Disruption of cellular compartmentalization accelerates fresh-cut browning of S28. • High expression of Phenylpropanoid biosynthesis promotes fresh-cut browning of S28. [ABSTRACT FROM AUTHOR]