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.

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.

Anthocyanins are water-soluble flavonoid pigments that play a crucial role in plant growth and metabolism. They serve as attractants for animals by providing plants with red, blue, and purple pigments, facilitating pollination and seed dispersal. The fruits of solanaceous plants, tomato (Solanum lycopersicum) and eggplant (Solanum melongena), primarily accumulate anthocyanins in the fruit peels, while the ripe fruits of Atropa belladonna (Ab) have a dark purple flesh due to anthocyanin accumulation. In this study, an R2R3-MYB transcription factor (TF), AbMYB1, was identified through association analysis of gene expression and anthocyanin accumulation in different tissues of A. belladonna. Its role in regulating anthocyanin biosynthesis was investigated through gene overexpression and RNA interference (RNAi). Overexpression of AbMYB1 significantly enhanced the expression of anthocyanin biosynthesis genes, such as AbF3H, AbF3′5′H, AbDFR, AbANS, and Ab3GT, leading to increased anthocyanin production. Conversely, RNAi-mediated suppression of AbMYB1 resulted in decreased expression of most anthocyanin biosynthesis genes, as well as reduced anthocyanin contents in A. belladonna. Overall, AbMYB1 was identified as a fruit-expressed R2R3-MYB TF that positively regulated anthocyanin biosynthesis in A. belladonna. This study provides valuable insights into the regulation of anthocyanin biosynthesis in Solanaceae plants, laying the foundation for understanding anthocyanin accumulation especially in the whole fruits of solanaceous plants.

Ornithine decarboxylase (ODC) is the rate-limiting enzyme in the biosynthesis of polyamines and plant alkaloids, including medicinal tropane alkaloids (TAs). Due to its key role, ODC has been utilized as an effective molecular tool in metabolic engineering. However, to date, only a limited number of plant ODCs have been characterized. Among the reported ODCs, Erythroxylum coca ODC (EcODC) exclusively has ODC activity, while Nicotiana glutinosa ODC (NgODC) exhibits dual ODC and lysine decarboxylase (LDC) activities. The potential LDC activity of ODCs from TA-producing plants remains unknown. Here, we characterized AlODC and DsODC from Anisodus luridus and Datura stramonium, along with two previously reported ODCs from Atropa belladonna (AbODC) and Hyoscyamus niger (HnODC), in Escherichia coli to investigate their enzyme kinetics and substrate specificity. Enzymatic assays revealed that both AlODC and DsODC catalyzed the conversion of ornithine to putrescine, confirming their ODC activity, with AlODC exhibiting a higher catalytic efficiency, comparable to established ODCs. Furthermore, all four ODCs also displayed LDC activity, albeit at significantly lower efficiency (<1% of ODC activity). This study provides a comprehensive analysis of the enzyme kinetics of ODCs from TA-producing plants, identifying promising candidate genes for metabolic engineering for the biomanufacturing of putrescine-derived alkaloids. Moreover, this is the first report of LDC activity in ODCs from Solanaceae TA-producing plants, shedding light on the evolutionary relationship between ODC and LDC.

Ornithine decarboxylase (ODC) functions as the rate-limiting enzyme in the polyamine (PA) biosynthetic pathway. It catalyzes the decarboxylation of L-ornithine to produce putrescine, thereby initiating the biosynthesis of polyamines. Polyamines are a class of widely distributed polycationic aliphatic compounds in living organisms, including putrescine, spermidine, and spermine. They serve not only as critical regulators of cell growth, proliferation, and differentiation, but also as important signaling molecules involved in plant responses to environmental stress and key precursors in the biosynthesis of diverse secondary metabolites. Focusing on recent advances in plant ODC research, this review summarizes the characteristics and evolutionary relationships of the ODC gene family, the biochemical properties and catalytic mechanism of the enzyme, and its multiple physiological roles in growth, development, secondary metabolism, and stress adaptation. Furthermore, we discuss the complex regulatory mechanisms governing ODC activity at both transcriptional and post-translational levels, with a critical gap in understanding the post-translational regulation of ODC in plants, particularly the mechanisms governing its degradation. Unlike in animals, where antizymes mediate ODC degradation, functional analogs of antizymes have not yet been identified in plants, leaving the degradation pathway largely unexplored. Finally, we review the applications of plant genetic modification targeting ODC in enhancing the production of valuable secondary metabolites in medicinal plants and improving stress tolerance in crops, along with perspectives on future research directions. This review illustrates the diversity of ODC functions and the complexity of its regulatory mechanisms in plant growth, development, stress responses, and secondary metabolism. It also provides a theoretical foundation and insights for exploring ODC as a target for plant genetic modification, which is promising for improving the economic traits and stress resistance of horticultural plants.