Paeonia peregrina Mill Petals as a New Source of Biologically Active Compounds: Chemical Characterization and Skin Regeneration Effects of the Extracts.

Paeonia peregrina Mill. is a perennial herbaceous plant species, known for the medicinal value of all of its plant parts, although the chemical composition of the petals is unknown. This study aimed to determine the chemical fingerprint of the petals and also establish the optimal extraction parameters, extraction medium, and extraction method for petals collected from different localities in Serbia. The optimization was performed in order to acquire extracts that are rich in the contents of total polyphenol content (TPC) and total flavonoid content (TFC), and also exhibit strong antioxidant activity. In addition, the influence of the extracts on several human skin pathogens was evaluated, as well as their ability to aid wound closure and act as anti-inflammatory agents. Both the extraction medium and the applied technique significantly influenced the skin-beneficial biological activities, while methanol proved to be a more favorable extraction medium. In conclusion, the extraction conditions that yielded the extract with the richest phenolic content with satisfactory biological potential varied between the assays, while the most promising locality in Serbia for the collection of P. peregrina petals was Pancevo (South Banat).

Comparative transcriptome sequencing analysis to postulate the scheme of regulated leaf coloration in Perilla frutescens.

Perilla as herb, ornamental, oil and edible plant is widely used in East Asia. Until now, the mechanism of regulated leaf coloration is still unclear. In this study, four different kinds of leaf colors were used to measure pigment contents and do transcriptome sequence to postulate the mechanism of leaf coloration. The measurements of chlorophyll, carotenoid, flavonoid, and anthocyanin showed that higher contents of all the aforementioned four pigments were in full purple leaf 'M357', and they may be determined front and back leaf color formation with purple. Meanwhile, the content of anthocyanin was controlled back leaf coloration. The chromatic aberration analysis and correlative analysis between different pigments and L*a*b* values analysis also suggested front and back leaf color change was correlated with the above four pigments. The genes involved in leaf coloration were identified through transcriptome sequence. The expression levels of chlorophyll synthesis and degradation related genes, carotenoid synthesis related genes and anthocyanin synthesis genes showed up-/down-regulated expression in different color leaves and were consistent of accumulation of these pigments. It was suggested that they were the candidate genes regulated perilla leaf color formation, and genes including F3'H, F3H, F3',5'H, DFR, and ANS are probably important for regulating both front and back leaf purple formation. Transcription factors involved in anthocyanin accumulation, and regulating leaf coloration were also identified. Finally, the probable scheme of regulated both full green and full purple leaf coloration and back leaf coloration was postulated.

Effects of Partial Replacement of NaCl with KCl on Protein Properties and Quality Attributes of Lightly Salted Tilapias Fillets.

The evolution of quality attributes and their association with the protein properties of lightly tilapias fillets salted with different replacement proportions of NaCl with KCl (0%, 10%, 30%, 50%, 70%, 100%) at the same ionic strength were investigated. KCl replacements using optimal substitution (50% of KCl) contributed to maintaining desired quality properties. Further, KCl replacement (about 50~70% of KCl) led to the insolubilization and weakened stability of myofibrillar proteins, represented by the unfolding of the myofibrillar protein, increased surface hydrophilic points, and strengthened internal protein-protein interaction, resulting in the structurally reinforced hardness and lower water-holding capacity. Excessive replacement (more than 70% of KCl) showed apparent deterioration in taste quality, coloration, and hardness received by sensory sensation caused by immoderate hydrolysis and aggravated oxidation of the myofibrillar protein. In this sense, insights into KCl replacements on protein properties might be a positive approach to improving quality attributes of lightly salted tilapias fillets.

The red/blue light ratios from light-emitting diodes affect growth and flower quality of Hippeastrum hybridum 'Red Lion'.

Light quality strongly impacts the growth and flower quality of ornamental plants. The optimum light quality for the growth and flowering of Hippeastrum remains to be validated. In the present study, we investigated the effect of the red/blue light ratio of LEDs on the growth and flowering quality of H. hybrid 'Red Lion'. Two LEDs with red/blue light ratio of 1:9 (R10B90) and 9:1 (R90B10) were designed. LEDs of white light were the control. In the earlier vegetative and reproductive growth phase, R90B10 increased the biomass of the bulbs, leaves, and flowers. Compared with the control and R10B90 group, R90B10 LEDs delayed flowering by 2.30 d and 3.26 d, respectively. Based on chlorophyll contents, photosynthetic capacity, chlorophyll fluorescence parameters, and carbohydrate contents, the photosynthesis rate was higher in the R10B90 group. Optimal red and blue light intensity promoted the accumulation of carbohydrates and early flowering and prolonged the flowering period of H. hybrid. Microscopic analysis showed that stomatal density was high, and the number of chloroplasts was large in the R10B90 treatment group, which enhanced photosynthesis. Particularly, R10B90 promoted the expression of seven key genes related to chlorophyll synthesis. R10B90 also promoted early overexpression of the HpCOL gene that promotes early flowering. Thus, higher blue light and 10% red light intensities promote early and extended flowering, while higher red light and 10% blue light promote vegetative plant growth but delay flowering.

Karyotype Analysis, Genomic and Fluorescence In Situ Hybridization (GISH and FISH) Reveal the Ploidy and Parental Origin of Chromosomes in Paeonia Itoh Hybrids.

Itoh hybrids are intersectional hybrids in Paeonia L. with sect. Moutan and sect. Paeonia as paternal and maternal parents, respectively. Therefore, these hybrids have herbaceous stems with improved ornamental value introduced by the paternal parent. Although both of their parents are diploids, Itoh hybrids are triploids. Moreover, the parental origin of their chromosomes has not been extensively studied. This study systematically analyzed the genome size, ploidy, and karyotype of Itoh hybrids and compared them with their parental taxa. Although the monoploid genome size of Itoh hybrids was different, it was not significantly different from that of the parents. However, the size of varieties in the two parental taxa was significantly different from the wild species, probably due to genome rearrangements caused by artificial selection. Further karyotype analysis, correlation analysis, and hierarchical clustering could not identify the parental origin of chromosomes in Itoh hybrids. Verification through genomic and fluorescence in situ hybridization (GISH and FISH) suggested that for the three sets of chromosomes in Itoh hybrids, two were from the paternal parent, and one was from the maternal parent. One of the first two sets was from wild species, and the other from a cultivated variety. GISH could not label the chromosomes of cultivated peonies from the sect. Moutan, probably due to the huge and complex genomes compared with the wild species. Meanwhile, 5S rDNA-based FISH was first applied in Paeonia, which may be used for ploidy assessment. This work may give insights into the utilization of Itoh hybrid resources.

Nutrient Supply Is Essential for Shifting Tree Peony Reflowering Ahead in Autumn and Sugar Signaling Is Involved.

The flowering time of tree peony is short and concentrated in spring, which limits the development of its industry. We previously achieved tree peony reflowering in autumn. Here, we further shifted its reflowering time ahead through proper gibberellin (GA) treatment plus nutrient supply. GA treatment alone initiated bud differentiation, but it aborted later, whereas GA plus nutrient (G + N) treatment completed the opening process 38 days before the control group. Through microstructural observation of bud differentiation and starch grains, we concluded that GA plays a triggering role in flowering induction, whereas the nutriment supply ensured the continuous developing for final opening, and both are necessary. We further determined the expression of five floral induction pathway genes and found that PsSOC1 and PsLFY probably played key integral roles in flowering induction and nutrient supply, respectively. Considering the GA signaling, PsGA2ox may be mainly involved in GA regulation, whereas PsGAI may regulate further flower formation after nutrient application. Furthermore, G + N treatment, but not GA alone, inhibited the expression of PsTPS1, a key restricting enzyme in sugar signaling, at the early stage, indicating that sugar signaling is also involved in this process; in addition, GA treatment induced high expression of PsSnRK1, a major nutrient insufficiency indicator, and the induction of PsHXK1, a rate-limiting enzyme for synthesis of sugar signaling substances, further confirmed the nutrient shortage. In short, besides GA application, exogenous nutrient supply is essential to shift tree peony reflowering ahead in autumn under current forcing culture technologies.

DNA Demethylation Induces Tree Peony Flowering with a Low Deformity Rate Compared to Gibberellin by Inducing PsFT Expression under Forcing Culture Conditions.

Gibberellin (GA) is frequently used in tree peony forcing culture, but inappropriate application often causes flower deformity. Here, 5-azacytidine (5-azaC), an efficient DNA demethylating reagent, induced tree peony flowering with a low deformity rate by rapidly inducing PsFT expression, whereas GA treatment affected various flowering pathway genes with strong pleiotropy. The 5-azaC treatment, but not GA, significantly reduced the methylation level in the PsFT promoter with the demethylation of five CG contexts in a 369 bp CG-rich region, and eight light-responsive related cis-elements were also predicted in this region, accompanied by enhanced leaf photosynthetic efficiency. Through GO analysis, all methylation-closer differentially expressed genes (DEGs) were located in the thylakoid, the main site for photosynthesis, and were mainly involved in response to stimulus and single-organism process, whereas GA-closer DEGs had a wider distribution inside and outside of cells, associated with 12 categories of processes and regulations. We further mapped five candidate DEGs with potential flowering regulation, including three kinases (SnRK1, WAK2, and 5PTase7) and two bioactive enzymes (cytochrome P450 and SBH1). In summary, 5-azaC and GA may have individual roles in inducing tree peony flowering, and 5-azaC could be a preferable regulation approach; DNA demethylation is suggested to be more focused on flowering regulation with PsFT playing a core role through promoter demethylation. In addition, 5-azaC may partially undertake or replace the light-signal function, combined with other factors, such as SnRK1, in regulating flowering. This work provides new ideas for improving tree peony forcing culture technology.

Acidic and Alkaline Conditions Affect the Growth of Tree Peony Plants via Altering Photosynthetic Characteristics, Limiting Nutrient Assimilation, and Impairing ROS Balance.

Exposure to acidic and alkaline conditions were found to cause the excess accumulation of reactive oxygen species in tree peony, thereby causing damage and inhibiting plant growth and development. The activities of antioxidant enzymes were also found to be significantly up-regulated, especially under alkaline conditions; this explained why tree peony is better adapted to alkaline than to acidic conditions. Through pairwise comparisons, 144 differentially expressed genes (DEGs) associated with plant growth, photosynthesis, and stress were identified. The DEGs related to stress were up-regulated, whereas the remaining DEGs were almost all down-regulated after acid and alkaline treatments. The nutrient assimilation was greatly inhibited. Chlorophyll synthesis genes were suppressed, and chlorophyll content was reduced. The development and structures of stomata and chloroplasts and the transcription of related genes were also influenced. Among photosynthesis-related DEGs, electron transport chains were the most sensitive. The suppressed expression of photosynthesis genes and the reduced light-harvesting capacity, together with the impairment of chloroplasts and stomata, finally led to a sharp decrease in the net photosynthetic rate. Carbohydrate accumulation and plant biomass were also reduced. The present study provides a theoretical basis for the response mechanisms of tree peony to adverse pH conditions and enriches knowledge of plant adaptation to alkaline conditions.

Non-structural carbohydrates coordinate tree peony flowering both as energy substrates and as sugar signaling triggers, with the bracts playing an essential role.

The natural fluorescence of tree peony is short. Forcing culture, mainly by defoliation and gibberellin (GA) treatment, is frequently used for its industrial production. We previously found forcing culture to be coordinated by non-structural carbohydrates (NSCs). Herein, we further revealed the specific role of NSCs during this process. We observed that both defoliation and GA treatment increased the photosynthesis in the bracts, and defoliation had a greater effect on NSC assimilation. We further determined the NSC content and PsSWEETs expression in the bracts, and the results indicated that GA may contribute more to NSC allocation by inducing PsSWEET7. Furthermore, we determined the trehalose-6-phosphate (T6P) content and sugar signaling-related gene (PsTPS1, PsSnRK1, and PsHXK1) expression in both the petals and bracts and found that both defoliation and GA treatment induced T6P levels as well as PsTPS1 expression in both tissues. This indicated that the sugar signaling pathway may also be involved in NSC-coordinated tree peony flowering. In particular, PsSnRK1 was more rapidly induced in the bracts (as an energy shortage response) in the control plants and was completely prohibited by defoliation and GA treatment, indicating the key role of the bracts in sugar signaling. In conclusion, NSCs induced tree peony flowering both as an energy substrate and sugar signaling trigger, with the bracts playing an essential role. These results may provide further evidence on the mechanism of NSC-coordinated flower opening in tree peony under forcing culture conditions, which may also provide a foundation for improving this technology.

Seed Proteomic Profiles of Three Paeonia Varieties and Evaluation of Peony Seed Protein as a Food Product.

Peony (Paeonia) has high ornamental, edible, and medicinal values. In order to distinguish seeds varieties, describe the proteomic profiles correlated with stress tolerance, and evaluate peony seed protein (PSP) as a functional food product, we characterized the seed protein profiles of these three species and their glucosidase inhibition activities. Results showed that the intensity of protein bands in sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and specific protein ID (especially for specifically expressed proteins (SEPs)) was effective to distinguish these peony seed varieties. Proteomic analysis of the three species showed that P. ostii "Fengdan" has heat and pathogen tolerance-related proteins, while P. rockii has higher content of proteins related to cold resistance, which were all highly consistent with their adaptation of heat or cold habitat. Moreover, stress-related proteins were also accumulated in P. lactiflora Pall "Hangshao" seeds, showing its potential for stress resistance. Further protein analysis showed that the primary composition of PSP was albumin and globulin. And the solubility of PSP was good. Furthermore, PSP also showed high glucosidase inhibition activity, indicating that PSP might have some potential function for the remission of hyperglycemia. And P. ostii "Fengdan" seeds may be a better source for protein production than seeds of the other two species in terms of protein solubility and the content of total protein, albumin, and globulin. In addition, an optimal protocol of microwave-assisted alkali extraction was developed to produce PSP. In conclusion, the evaluated stress-related proteins in three peony seed species by proteomic analysis quite agreed with their adaptation of heat or cold stress; proteomics could also be a very useful tool for distinguishing species in the production; and peony seeds may be a good source for protein production.

Composition of peony petal fatty acids and flavonoids and their effect on Caenorhabditis elegans lifespan.

The colorful petals of tree peony (Paeonia suffruticosa Andrews) are widely used as a source of additives in food, fragrances, and cosmetics. However, the nutritional composition of peony petals is undetermined, thereby limiting utility and product development. In this work, fresh petals of 15 traditional Chinese tree peony cultivars were selected to analyze the composition of soluble sugars, starch, and soluble protein. Extracted fatty acids (FAs) and flavonoids from petals were characterized by GC-MS and UPLC-triple-TOF-MS, respectively. The oxidative stress resistance (generated by paraquat) effects of petal extracts of three cultivars were also investigated in the model organism Caenorhabditis elegans. Our results showed that the petals were highly enriched in soluble sugars. 11 FAs were found in tree peony petals, and their compositions were similar to that of tree peony seeds. A total of 56 flavonoids were detected in tree peony petals, 28 of which were reported for the first time in tree peony petals, indicating that UPLC-triple-TOF-MS can improve the identification efficiency of flavonoids. Further analysis of tree peony petal metabolites indicated that anthocyanidin and flavonol composition might be used as specific chemotaxonomic biomarkers for cultivar classification. Flavonoids, linoleic acid, and α-linolenic acid (ALA) in petals might provide antioxidant activity. 150 mg/L of petal extracts of all three tested cultivars increased the lifespan of C. elegans. It was suggested that the petal extracts possessed anti-aging effects and oxidative stress resistance. These results highlight that tree peony petals can serve as natural antioxidant food resources in the future.

Effects of Casein, Chicken, and Pork Proteins on the Regulation of Body Fat and Blood Inflammatory Factors and Metabolite Patterns Are Largely Dependent on the Protein Level and Less Attributable to the Protein Source.

The impact of meat protein on metabolic regulation is still disputed and may be influenced by protein level. This study aimed to explore the effects of casein, pork, and chicken proteins at different protein levels (40% E vs 20% E) on body weight regulation, body fat accumulation, serum hormone levels, and inflammatory factors/metabolites in rats maintained on high-fat (45% E fat) diets for 84 d. Increased protein levels resulted in a significant reduction in body fat mass and an increase in the serum levels of the anti-inflammatory cytokine IL-10, independent of protein source. Analysis of blood via untargeted metabolomics analysis identified eight, four, and four metabolites significantly altered by protein level, protein source, and a protein level-source interaction, respectively. Together, the effects of casein, chicken, and pork protein on the regulation of body fat accumulation and blood metabolite profile are largely dependent on protein level and less attributable to the protein source.

Molecular characterization and expression analysis of the SQUAMOSA PROMOTER BINDING PROTEIN-LIKE gene family in Paeonia suffruticosa.

KEY MESSAGE: A total of 16 PsSPL genes were identified in tree peony. PsSPLs potentially regulated flowering time, lateral bud and seed development, and the juvenile-to-adult phase transition. SQUAMOSA PROMOTER BINDING PROTEIN-LIKE (SPL) transcription factors are important for plant growth and development. Here, we report the identification of 16 full-length PsSPLs in tree peony (Peaonia suffruticosa Andr.) and 9 PsSPLs that have miR156 target sites. Phylogenetic analysis of the relationship of SPLs in P. suffruticosa and Arabidopsis suggested that they can be classified into six groups, and PsSPLs were highly correlated with Arabidopsis SPLs counterparts in the same group. Cis-element of promoter region analysis suggested that PsSPL genes play roles in physiological processes and developmental events. Expression analysis indicated that most PsSPL genes exhibited high expression levels in the tissues and organs examined here. The increasing expression levels of PsSPL1, PsSPL2, PsSPL8, PsSPL9, PsSPL12, and PsSPL16, and decreasing expression levels of PsSPL1A and PsSPL1B in buds over time suggested that they were probably regulated by the juvenile-to-adult phase transition. In addition, the expression profiles of PsSPL genes in different developmental buds and seeds suggested that PsSPL2, PsSPL3, PsSPL9, PsSPL10, PsSPL13, and PsSPL13A were important genes for regulating the flowering time of the tree peony; PsSPL2 and PsSPL8 might play a role in suppressing lateral bud development, and PsSPL2, PsSPL13, and PsSPL14 positively controlled grain size and number, and pod branching. These results provide a foundation for future functional analysis of PsSPL genes in tree peony growth and development.

Defoliation, not gibberellin, induces tree peony autumn reflowering regulated by carbon allocation and metabolism in buds and leaves.

Short and concentrated natural fluorescence hinders tree peony (Paeonia suffruticosa) annual production, and defoliation and gibberellin (GA) application is used to induce its reflowering in autumn. Here, the individual roles of defoliation and GA treatment were determined by monitoring morphological and soluble sugar changes in buds and leaves, and by investigating carbon allocation- and metabolism-related gene expression. Both defoliation and GA treatment induced early bud development, but induction was faster using the GA treatment. Only defoliation, not GA treatment, induced the final reflowering, although their combination accelerated it. Furthermore, defoliation decreased the sucrose content in buds much faster than the GA treatment. This sucrose reduction may play a key role in tree peony reflowering, and the higher carbon metabolism activity in young leaves after defoliation may further help the reflowering process. Defoliation enhanced the expression of sucrose transporters PsSUT4 and PsSWEET12 in buds, and their expression in young leaves was greater than after GA treatment. This indicated that PsSUT4 and PsSWEET12 may help transport carbon into buds after defoliation. In addition, the invertases, PsCIN2 and PsCWIN1 in young leaves were more highly expressed after defoliation, indicating that they may contribute to reflowering after defoliation by accelerating sucrose hydrolysis in young leaves. In addition, the expression levels of PsVIN1 and PsVIN2 in leaves, and PsVIN2 in buds were more highly induced by GA treatment than by defoliation, indicating that PsVINs may mainly respond to GA treatment. These results may help improve the tree peony forcing culture technology and related industrial production.

Transcriptome sequencing and identification of key callus browning-related genes from petiole callus of tree peony (Paeonia suffruticosa cv. Kao) cultured on media with three browning inhibitors.

Tree peony (Paeonia suffruticosa Andrews) has ornamental, oil, and medicinal values, and demand in the markets for uniform tree peony seedlings is increasing. Micropropagation could quickly propagate uniform seedlings. However, the heavy browning phenomenon hinders large-scale development of uniform tree peony seedlings. In this paper, we measured the total phenolic compounds content, and sequenced the transcriptomes of tree peony 'Kao' petiole calluses cultured on media with three browning antagonist treatments and fresh petioles to identify the key genes involved in callus browning. Polyvinylpyrrolidone (PVP) treatment can reduce production of phenolic compounds and promote callus regeneration. A total of 218,957 unigenes were obtained from fresh petiole and three kinds of browning petiole calluses by transcriptome sequencing. The average sequence length of unigenes was 446 bp with an N50 of 493 bp. Functional annotation analysis revealed that 43,428, 45,357, 31,194, 30,019, and 21,357 unigenes were annotated using the NCBI-NR database, Swiss-Prot, KOG, GO, and KEGG, respectively. In total, 33 differentially expressed genes (DEGs) were identified as potentially associated with callus browning. Among these DEGs, 12 genes were predicted to participate in phenolic compounds biosynthesis, three genes were predicted to be involved in phenolic compounds oxidation, and six genes were predicted to participate in callus regeneration. Moreover, six transcription factors were observed to be differentially expressed in the fresh petiole and three treated petioles in tree peony. This study comprehensively identifies browning-related gene resources and will possibly help in deciphering the molecular mechanisms of callus browning of tree peony in the future.

Dry storage improves the vase quality of cut peony by increasing water uptake efficiency through aquaporins regulation.

Proper storage prolongs peony market supply. Here, we determined the changes in fresh weight and expression of four aquaporin genes under dry storage (DS) and wet storage (WS). It has showed that after harvesting, the fresh weight change was accompanied with flower opening. After both short- and long-term of storage, the water uptake efficiency in DS group was greater during the first few vase days, providing a direct material basis of DS improved vase quality. The gene expression results showed that PlPIP1;3 and PlTIP2;1 were mainly expressed in petals, whereas PlNIP1;2-like and PlSIP2;1 were mainly expressed in the green tissues. In addition, the expression of PlTIP2;1 in the petals was consistent with the flower opening process, indicating that it may play a major role in facilitating water uptake. During cold storage, the expression of PlPIP1;3 and PlTIP2;1 was higher or more rapidly induced in the DS group, and thus we deduced that they play important roles in improving the vase quality of DS. Furthermore, the expression of PlNIP1;2-like in the early stage of the DS group was more stable than in WS, which may also be partially responsible for the vase quality improvement. In contrast, PlSIP2;1 may not be involved, since no significant change was observed between the DS and WS group. In short, the expression of PlPIP1;3 and PlTIP2;1 in the DS group during storage may improve water uptake efficiency during the vase period and then improving the vase quality of cut peony.

De novo sequencing of tree peony (Paeonia suffruticosa) transcriptome to identify critical genes involved in flowering and floral organ development.

BACKGROUND: Tree peony (Paeonia suffruticosa Andrews) is a globally famous ornamental flower, with large and colorful flowers and abundant flower types. However, a relatively short and uniform flowering period hinders the applications and production of ornamental tree peony. Unfortunately, the molecular mechanism of regulating flowering time and floral organ development in tree peony has yet to be elucidated. Because of the absence of genomic information, 454-based transcriptome sequence technology for de novo transcriptomics was used to identify the critical flowering genes using re-blooming, non-re-blooming, and wild species of tree peonies. RESULTS: A total of 29,275 unigenes were obtained from the bud transcriptome, with an N50 of 776 bp. The average length of unigenes was 677.18 bp, and the longest sequence was 5815 bp. Functional annotation showed that 22,823, 17,321, 13,312, 20,041, and 9940 unigenes were annotated by NCBI-NR, Swiss-Prot, COG, GO, and KEGG, respectively. Within the differentially expressed genes (DEGs) 64 flowering-related genes were identified and some important flowering genes were also characterized by bioinformatics methods, reverse transcript polymerase chain reaction (RT-PCR), and rapid-amplification of cDNA ends (RACE). Then, the putative genetic network of flowering induction pathways and a floral organ development model were put forward, according to the comparisons of DEGs in any two samples and expression levels of the important flowering genes in differentiated buds, buds from different developmental stages, and with GA or vernalization treated. In tree peony, five pathways (long day, vernalization, autonomous, age, and gibberellin) regulated flowering, and the floral organ development followed an ABCE model. Moreover, it was also found that the genes PsAP1, PsCOL1, PsCRY1, PsCRY2, PsFT, PsLFY, PsLHY, PsGI, PsSOC1, and PsVIN3 probably regulated re-blooming of tree peony. CONCLUSION: This study provides a comprehensive report on the flowering-related genes in tree peony for the first time and investigated the expression levels of the critical flowering related genes in buds of different cultivars, developmental stages, differentiated primordium, and flower parts. These results could provide valuable insights into the molecular mechanisms of flowering time regulation and floral organ development.

Defoliation and gibberellin synergistically induce tree peony flowering with non-structural carbohydrates as intermedia.

Although the natural florescence of the tree peony is short, it can be lengthened by forcing culture. In this study, both defoliation or gibberellic acid (GA3) treatment individually induced tree peony (Paeonia suffruticosa 'Luo Yang Hong') flowering under forcing culture, and their combination (D + G) accelerated flowering with a GA3-overdose-like phenomenon, indicating that synergism between defoliation and GA3 treatment may occur. Both defoliation and GA3 treatment induced a GA response, including (i) increased GA3 production, (ii) increased PsCPS and PsGA3ox expression, and (iii) decreased PsGA2ox, PsGID1c, and PsGID2 expression; both treatments also positively influenced non-structural carbohydrate (NSC) accumulation. According to the expression of five PsSWEETs, PsSWEET2 and PsSWEET17 may redundantly exercise the crosstalk of defoliation and GA3 treatment by NSC distribution, whereas PsSWEET12 may act by GA modulation; no synergism resulting from the D + G treatment was detected. Tissue-specific analysis indicated that, in sepals, PsSWEET2 and PsSWET7 are both induced by defoliation and GA3 treatment, whereas PsSWEET2 expression showed synergism with the D + G treatment. In summary, defoliation and GA3 treatment synergistically induce tree peony flowering under forcing culture, and NSCs are suggested as key intermedia. Moreover, sepals may play key roles in their synergism, although more direct evidence is still needed.

Elucidation of the mechanism of reflowering in tree peony (Paeonia suffruticosa) 'Zi Luo Lan' by defoliation and gibberellic acid application.

In this study, the reflowering mechanism of tree peony (Paeonia suffruticosa 'Zi Luo Lan') after defoliation and gibberellic acid (GA) application (autumn-flowering treatment) was investigated by monitoring the morphological changes, measuring the endogenous GA3 and abscisic acid (ABA) contents, and determining the expression patterns of six GA- and two ABA-related genes. The results show that autumn-flowering treatment induced tree peony reflowering in autumn, which was accompanied by nutrient absorption in buds. The application of exogenous GA3 induced a simultaneous increase in GA3 and decrease in ABA levels, suggesting that the high ratios of GA3/ABA may play a key role in inducing tree peony reflowering. RT-qPCR analysis shows that PsCPS and PsGA2ox were significantly induced and inhibited by GA3 application, respectively, which supports the hypothesis that GA3 treatment induces endogenous GA3 production. In addition, GA3 treatment inhibited the expression of the PsGID1c, but its effect on PsGAI1 was limited, whereas the expression of PsGAMYB could be GA- or ABA-related. Furthermore, autumn-flowering treatment significantly inhibited the expression of PsNCED and PsbZIP, which coincides with the observed changes in ABA levels. Therefore, we postulate that autumn-flowering treatment induces tree peony reflowering by inhibiting the function of ABA accumulation and signaling.

Proteomic analysis of tree peony (Paeonia ostii 'Feng Dan') seed germination affected by low temperature.

Seed germination is a critical process that is influenced by various factors. In the present study, the effect of low temperature (4 °C) on tree peony seed germination was investigated. Compared to seeds maintained at 25 °C, germination was inhibited when seeds were kept at 4 °C. Furthermore, low-temperature exposure of seeds resulted in a delay in water uptake, starch degradation, and soluble sugar consumption and a subsequent increase in soluble protein levels. Two-dimensional gel electrophoresis (2-DE) proteomic analysis identified 100 protein spots. Comparative analysis indicated that low-temperature exposure apparently mainly affected glycolysis and the tricarboxylic acid (TCA) cycle, while also significantly affecting proteometabolism-related factors. Moreover, low-temperature exposure led to the induction of abscisic acid, whereas the gibberellin pathway was not affected. Further comparison of the two temperature conditions showed that low-temperature exposure delays carbohydrate metabolism, adenosine triphosphate (ATP) production, respiration, and proteolysis and increases defense response factors. To further examine the obtained proteomic findings, four genes were evaluated by quantitative polymerase chain reaction (qPCR). The obtained transcriptional results for the GAPC gene coincided with the translational results, thus further suggesting that the delay in glycolysis may play a key role in low-temperature-induced inhibition of seed germination. However, the other three genes examined, which included FPP synthase, PCNT115, and endochitinase, showed non-correlative transcriptional and translational profiles. Our results suggest that the exposure of tree peony seeds to low temperature results in a delay in the degradation of starch and other metabolites, which in turn affects glycolysis and some other processes, thereby ultimately inhibiting seed germination.