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Background Sufficient low temperature accumulation is the key strategy to break bud dormancy and promote subsequent flowering in tree peony anti-season culturing production. Exogenous gibberellins (GAs) could partially replace chilling to accelerate dormancy release, and different kinds of GAs showed inconsistent effects in various plants. To understand the effects of exogenous GA 3 and GA 4 on dormancy release and subsequent growth, the morphological changes were observed after exogenous GAs applications, the differentially expressed genes (DEGs) were identified, and the contents of endogenous phytohormones, starch and sugar were measured, respectively. Results Morphological observation and photosynthesis measurements indicated that both GA 3 and GA 4 applications accelerated bud dormancy release, but GA 3 feeding induced faster bud burst, higher shoot and more flowers per plant. Full-length transcriptome of dormant bud was used as the reference genome. Totally 124 110 459, 124 015 148 and 126 239 836 reads by illumina transcriptome sequencing were obtained in mock, GA 3 and GA 4 groups, respectively. Compared with the mock, there were 879 DEGs and 2 595 DEGs in GA 3 and GA 4 group, 1 179 DEGs in GA 3 vs GA 4 , and 849 DEGs were common in these comparison groups. The significant enrichment KEGG pathways of 849 DEGs highlighted plant hormone signal transduction, starch and sucrose metabolism, cell cycle, DNA replication, etc. Interestingly, the contents of endogenous GA 1 , GA 3 , GA 4 , GA 7 and IAA significantly increased, ABA decreased after GA 3 and GA 4 treatments by LC–MS/MS. Additionally, the soluble glucose, fructose and trehalose increased after exogenous GAs applications. Compared to GA 4 treatment, GA 3 induced higher GA 1 , GA 3 and IAA level, more starch degradation to generate more monosaccharide for use, and promoted cell cycle and photosynthesis. Higher expression levels of dormancy-related genes, TFL , FT , EBB1 , EBB3 and CYCD, and lower of SVP by GA 3 treatment implied more efficiency of GA 3 . Conclusions Exogenous GA 3 and GA 4 significantly accelerated bud dormancy release and subsequent growth by increasing the contents of endogenous bioactive GAs, IAA, and soluble glucose such as fructose and trehalose, and accelerated cell cycle process, accompanied by decreasing ABA contents. GA 3 was superior to GA 4 in tree peony forcing culture, which might because tree peony was more sensitive to GA 3 than GA 4 , and GA 3 had a more effective ability to induce cell division and starch hydrolysis. These results provided the value data for understanding the mechanism of dormancy release in tree peony.

Background Black spot disease in tree peony caused by the fungal necrotroph A. alternata , is a primary limiting factor in the production of the tree peony. The intricate molecular mechanisms underlying the tree peony resistance to A. alternata have not been thoroughly investigated. Results The present study utilized high-throughput RNA sequencing (RNA-seq) technology to conduct global expression profiling, revealing an intricate network of genes implicated in the interaction between tree peony and A. alternata . RNA-Seq libraries were constructed from leaf samples and high-throughput sequenced using the BGISEQ-500 sequencing platform. Six distinct libraries were characterized. M1, M2 and M3 were derived from leaves that had undergone mock inoculation, while I1, I2 and I3 originated from leaves that had been inoculated with the pathogen. A range of 10.22–11.80 gigabases (Gb) of clean bases were generated, comprising 68,131,232 − 78,633,602 clean bases and 56,677 − 68,996 Unigenes. A grand total of 99,721 Unigenes were acquired, boasting a mean length of 1,266 base pairs. All these 99,721 Unigenes were annotated in various databases, including NR (Non-Redundant, 61.99%), NT (Nucleotide, 45.50%), SwissProt (46.32%), KEGG (Kyoto Encyclopedia of Genes and Genomes, 49.33%), KOG (clusters of euKaryotic Orthologous Groups, 50.18%), Pfam (Protein family, 47.16%), and GO (Gene Ontology, 34.86%). In total, 66,641 (66.83%) Unigenes had matches in at least one database. By conducting a comparative transcriptome analysis of the mock- and A. alternata -infected sample libraries, we found differentially expressed genes (DEGs) that are related to phytohormone signalling, pathogen recognition, active oxygen generation, and circadian rhythm regulation. Furthermore, multiple different kinds of transcription factors were identified. The expression levels of 10 selected genes were validated employing qRT-PCR (quantitative real-time PCR) to confirm RNA-Seq data. Conclusions A multitude of transcriptome sequences have been generated, thus offering a valuable genetic repository for further scholarly exploration on the immune mechanisms underlying the tree peony infected by A. alternata . While the expression of most DEGs increased, a few DEGs showed decreased expression.

Low propagation rate is the primary problem that limits industry development of tree peony. In this study, a highly efficient regeneration system for tree peony using somatic embryogenesis (SE) was established. The transcriptomes of zygotic embryo explants (S0), non-embryonic callus (S1), embryonic callus (S2), somatic embryos (S3), and regenerated shoots (S4) were analyzed to determine the regulatory mechanisms that underlie SE in tree peony. The differentially expressed genes (DEGs) were identified in the pairwise comparisons of S1-vs-S2 and S1-vs-S3, respectively. The enriched DEGs were primarily involved in hormone signal transduction, stress response and the nucleus (epigenetic modifications). The results indicated that cell division, particularly asymmetric cell division, was enhanced in S3. Moreover, the genes implicated in cell fate determination played central roles in S3. Hormone signal pathways work in concert with epigenetic modifications and stress responses to regulate SE. SERK, WOX9, BBM, FUS3, CUC, and WUS were characterized as the molecular markers for tree peony SE. To our knowledge, this is the first study of the SE of tree peony using transcriptome sequencing. These results will improve our understanding of the molecular mechanisms that underly SE in tree peony and will benefit the propagation and genetic engineering of this plant.

Tree peony ( Paeonia section Moutan DC.) produce strikingly large, vibrant blooms that exhibit remarkable morphological diversity, ranging from single petals to complex double forms, making them highly prized for ornamental horticulture. While auxin response factors (ARFs) are well-established as crucial regulators of organogenesis in model plants, the functional characterization of PoARF genes in tree peony remains largely unexplored. Genome-wide analysis identified 17 PoARF genes ( PoARF1 - PoARF17) in tree peony ( Paeonia ostii ). Their encoded proteins vary in length (420–993 aa) and molecular weight (47.2–109.8 kDa), with isoelectric points of 5.19–9.48 (mostly weakly acidic) and all predicted to localize to the nucleus. Phylogenetic analysis clustered the PoARFs into three clades (Groups I-III). All members contained eight conserved motifs (Motif1-7,9), indicating structural and functional conservation within this gene family. Gene architecture analysis revealed that most PoARF genes feature untranslated regions (UTRs) flanking both termini, while subgroup members exhibited remarkably similar exon–intron organizational patterns. Conserved sequence analysis result showed that the motif arrangement is relatively conserved within each subfamily. The promoter region of PoARF genes in tree peony contains four types of cis-regulatory elements, suggesting that it may be involved in biological processes such as light response, hormone regulation, and tissue-specific expression. The results of the instantaneous transformation test of tree peony showed that PoARF7 promotes petal development while inhibiting stamens development, whereas PoARF10 exhibits opposing functions. These results elucidate ARF-mediated control of floral organ ratios and provide a foundation for studying ARF genes family functions in woody angiosperms.

Tree peony (Paeonia Sect. Moutan) is a famous ornamental plant, with huge historical, cultural, and economic significance worldwide. In this study, we reported the ~13.79 Gb draft genome of a wide‐grown Paeonia suffruticosa cultivar “Luo shen xiao chun,” representing the largest sequenced genome in dicots to date. Phylogenetic analyses based on genome sequences demonstrated that P. suffruticosa was placed as sister to Vitales, and they together formed a clade that was sister to Rosids, weakly supporting a relationship of ((Saxifragales and Vitales) and Rosids). The identification and expression analysis of MADS‐box genes based on the genome assembly and de novo transcriptome assembly of P. suffruticosa revealed that the function of C class genes was restricted in flower development, which might be responsible for the stamen petalody in tree peony cultivars. Overall, the first sequenced genome in the family Paeoniaceae provides an important resource for the origin, domestication, and evolutionary study as well as cultivar breeding in tree peony. Tree peony (Paeonia Sect. Moutan) is a famous ornamental plant, with huge historical, cultural, and economic significance worldwide. The presented genome assembly in this study would serve as an important resource for functional genomic and genetic studies on tree peony, which would be useful for the conservation of endangered wild paeonia species and exploring the mechanisms of plant diversification and adaption under domestication in various environments.

An important family of transcription factors (TFs) in plants known as NAC (NAM, ATAF1/2, and CUC2) is crucial for the responses of plants to environmental stressors. In this study, we mined the NAC TF family members of tree peony (Paeonia suffruticosa Andrews) from genome-wide data and analyzed their response to heat and waterlogging stresses in conjunction with transcriptome data. Based on tree peony’s genomic information, a total of 48 PsNAC genes were discovered. Based on how similar their protein sequences were, these PsNAC genes were divided into 14 branches. While the gene structures and conserved protein motifs of the PsNAC genes within each branch were largely the same, the cis-acting elements in the promoter region varied significantly. Transcriptome data revealed the presence of five PsNAC genes (PsNAC06, PsNAC23, PsNAC38, PsNAC41, PsNAC47) and one PsNAC gene (PsNAC37) in response to heat and waterlogging stresses, respectively. qRT-PCR analysis reconfirmed the response of these five PsNAC genes to heat stress and one PsNAC gene to waterlogging stress. This study lays a foundation for the study of the functions and regulatory mechanisms of NAC TFs in tree peony. Meanwhile, the NAC TFs of tree peony in response to heat and waterlogging stress were excavated, which is of great significance for the selection and breeding of new tree peony varieties with strong heat and waterlogging tolerance.

Tree peonies (Paeonia Section Moutan)—including nine wild species, which belong to subsections Vaginatae and Delavayanae—are economically important plants with ornamental, nutritional, and medicinal applications. In this study, for the first time, we determined the bioactive components and antioxidant activities and antibacterial activities of the newly grown leaves of nine wild tree peony species (WTPS). A total of 276 bioactive components were identified through non-targeted metabolomics; more than 80% of the 276 metabolites identified are terpenoids and flavonoids. A total of 42 differential metabolites were quantitatively determined. The main differential metabolites were Paeoniflorin, Luteoloside, Hyperin, Apigenin-7-glucoside, Rhoifolin, and Cantharidin. Such a high terpenoid and flavonoid content of the leaf extracts renders them as species with strong antibacterial capacities, and most of the bacteria tested showed greater sensitivity derived from the members of subsection Vaginatae than those of subsection Delavayanae. All WTPS have significant antioxidant activity; this activity is attributed to high levels of the total phenolic content (TPC) and total flavonoid content (TFC), of which, among the nine WTPS, P. lutea has the strongest antioxidant capacity. Our results provided a theoretical basis for the in-deep application of tree peony leaves for food, medical, and pharmaceutical industries.

[This corrects the article DOI: 10.3389/fpls.2021.796181.].