Shan-Shan Li

α-Linolenic acid (ALA) is an essential fatty acid crucial for improving dietary nutrition in humans. Since ALA can only be obtained from dietary sources, developing ALA-rich biological resources is imperative. The seed oil of tree peony (Paeonia × suffruticosa), a promising woody oil crop, is particularly rich in ALA. In this study, we identified PsbZIP44, a basic leucine zipper (bZIP) transcription factor in tree peony, as a key regulator of ALA accumulation in seeds. Heterologous expression of PsbZIP44 in Arabidopsis (Arabidopsis thaliana) promoted ALA accumulation, and transient silencing in tree peony seeds decreased ALA levels. Additionally, we found that another bZIP transcription factor, PsbZIP9, negatively regulates ALA biosynthesis by inhibiting PsbZIP44 activity during the late stages of seed development. Based on these findings, we propose a model for FATTY ACID DESATURASE3 (PsFAD3) regulation in tree peony seeds, in which PsbZIP44 activates PsFAD3 during early seed development to promote ALA biosynthesis, while PsbZIP9 suppresses PsbZIP44 activity in later stages, limiting ALA accumulation. This study highlights the synergistic role of transcription factors in seed development, reveals the regulatory mechanisms of PsFAD3, and enhances our understanding of ALA biosynthesis. These findings provide a foundation for improving the quality of tree peony seed oil.

Benzenoids/phenylpropanoids, the second most diverse group of plant volatiles, exhibit significant structural diversity and play crucial roles in attracting pollinators and protecting against pathogens, insects, and herbivores. This review summarizes their complex biosynthetic pathways and regulatory mechanisms, highlighting their links to plant growth, development, hormone levels, circadian rhythms, and flower coloration. External factors like light, humidity, and temperature also influence their biosynthesis. Their ecological value is discussed, offering insights for enhancing floral scent, pollinator attraction, pest resistance, and metabolic engineering through genetic modification.

Xibei tree peony is a distinctive cultivar group that features red–purple blotches in petals. Interestingly, the pigmentations of blotches and non-blotches are largely independent of one another. The underlying molecular mechanism had attracted lots of attention from investigators, but was still uncertain. Our present work demonstrates the factors that are closely related to blotch formation in Paeonia rockii ‘Shu Sheng Peng Mo’. Non-blotch pigmentation is prevented by the silencing of anthocyanin structural genes, among which PrF3H, PrDFR, and PrANS are the three major genes. We characterized two R2R3-MYBs as the key transcription factors that control the early and late anthocyanin biosynthetic pathways. PrMYBa1, which belongs to MYB subgroup 7 (SG7) was found to activate the early biosynthetic gene (EBG) PrF3H by interacting with SG5 member PrMYBa2 to form an ‘MM’ complex. The SG6 member PrMYBa3 interacts with two SG5 (IIIf) bHLHs to synergistically activate the late biosynthetic genes (LBGs) PrDFR and PrANS, which is essential for anthocyanin accumulation in petal blotches. The comparison of methylation levels of the PrANS and PrF3H promoters between blotch and non-blotch indicated a correlation between hypermethylation and gene silencing. The methylation dynamics of PrANS promoter during flower development revealed a potential early demethylating reaction, which may have contributed to the particular expression of PrANS solely in the blotch area. We suggest that the formation of petal blotch may be highly associated with the cooperation of transcriptional activation and DNA methylation of structural gene promoters.

Floral scent is an important and genetically complex trait in horticultural plants. Tree peony (Paeonia × suffruticosa) originates in the Pan-Himalaya and have nine wild species divided into two subsections, Delavayanae and Vaginatae. Their flowers are beloved worldwide for their sweet floral fragrance, yet the flavor-related volatiles and underlying biosynthetic pathways remain unknown. Here, we characterized the volatile blends of all wild tree peony species and found that the flavor-related volatiles were highly divergent, but linalool was a unique monoterpene in subsect. Delavayanae. Further detection of volatiles in 97 cultivars with various genetic backgrounds showed that linalool was also the characteristic aroma component in P. delavayi hybrid progenies, suggesting that linalool was conserved and dominant within subsect. Delavayanae and its hybrids, instead of species and cultivars from subsect. Vaginatae. Global-transcriptome analysis of all wild tree peony species and 60 cultivars revealed five candidate genes that may be involved in key steps of linalool biosynthesis, especially the expressions of three TPS genes PdTPS1, PdTPS2 and PdTPS4 were significantly positively correlated with linalool emissions across tree peony cultivars. Further biochemical evidence demonstrated that PdTPS1 and PdTPS4 were the pivotal genes determining the species-specific and cultivar-specific emission of linalool. This study revealed a new insight into the floral scent divergence in tree peony and would greatly facilitate our understanding of phylogeny and evolution of Paeonia.

SUMMARY: Lotus plumule, the embryo of the seed of the sacred lotus (Nelumbo nucifera), contains a high accumulation of secondary metabolites including flavonoids and possesses important pharmaceutical value. Flavonoid C‐glycosides, which accumulate exclusively in lotus plumule, have attracted considerable attention in recent decades due to their unique chemical structure and special bioactivities. As well as mono‐C‐glycosides, lotus plumule also accumulates various kinds of di‐C‐glycosides by mechanisms which are as yet unclear. In this study we identified two C‐glycosyltransferase (CGT) genes by mining sacred lotus genome data and provide in vitro and in planta evidence that these two enzymes (NnCGT1 and NnCGT2, also designated as UGT708N1 and UGT708N2, respectively) exhibit CGT activity. Recombinant UGT708N1 and UGT708N2 can C‐glycosylate 2‐hydroxyflavanones and 2‐hydroxynaringenin C‐glucoside, forming flavone mono‐C‐glycosides and di‐C‐glycosides, respectively, after dehydration. In addition, the above reactions were successfully catalysed by cell‐free extracts from tobacco leaves transiently expressing NnCGT1 or NnCGT2. Finally, enzyme assays using cell‐free extracts of lotus plumule suggested that flavone di‐C‐glycosides (vicenin‐1, vicenin‐3, schaftoside and isoschaftoside) are biosynthesized through sequentially C‐glucosylating and C‐arabinosylating/C‐xylosylating 2‐hydroxynaringenin. Taken together, our results provide novel insights into the biosynthesis of flavonoid di‐C‐glycosides by proposing a new biosynthetic pathway for flavone C‐glycosides in N. nucifera and identifying a novel uridine diphosphate‐glycosyltransferase (UGT708N2) that specifically catalyses the second glycsosylation, C‐arabinosylating and C‐xylosylating 2‐hydroxynaringenin C‐glucoside.

Paeonia cultivars are famous ornamental plants, and some of them are also traditional Chinese medicinal resources. Intersubgeneric hybrids of Paeonia (IHPs) are formed by the hybridization of herbaceous peony (Paeonia lactiflora) and tree peony (Paeonia×suffruticosa or lutea hybrid tree peony). The phenotypic characteristics of IHPs are similar to those of herbaceous peony, and their root systems are large and vigorous. However, their medicinal value has not been reported yet. In this study, the roots of eight IHP samples were analyzed by high performance liquid chromatography quadrupole time‐of‐flight mass spectrometry (HPLC‐Q‐TOF‐MS/MS). A total of 18 compounds were identified, including phenols, paeonols, monoterpene glycosides, and tannins. The contents of monoterpene glycosides and tannins in IHPs were higher than herbaceous peony and tree peony, exceeding 44.76 mg/g DW and 11.50 mg/g DW, respectively. Three IHPs, ‘Prairie Charm’, ‘Garden Treasure’, and ‘Yellow Emperor’, with more types and a higher content of medicinal compounds, were screened out by cluster analysis. These IHPs have considerable potential for the development of medicinal resources.

Elm fruits were once an important food source in the years of famine. Research on the functional compounds in elm fruits was almost unavailable. In this study, we established an efficient high‐performance liquid chromatography method for the simultaneous separation of eight chlorogenic acids and 28 flavonoids in elm fruits for the first time. Total flavonoid contents ranged from 286 mg/100 g (Ulmus laciniata) to 1228 mg/100 g (U. pumila). High concentrations of rutin, quercetin 3‐O‐glucoside, and kaempferol derivatives were present in U. laevis, U. castaneifolia, and U. pumila, respectively. Furthermore, the fruit extracts of U. americana, U. castaneifolia, U. davidiana, and U. pumila showed higher antioxidant activity. These results suggest that fruits of these species can be used as bioresources for the extraction of the corresponding functional compounds. This work provides informative data and can be an important reference for future research on elm fruits as a renewed food resource.