Flowers In China Research Articles

SWATH-MS based proteomics reveals the role of photosynthesis related proteins and secondary metabolic pathways in the colored leaves of sweet olive (Osmanthus fragrans)

Colored leaves, a notable horticultural trait, have high research and ornamental value. The evergreen sweet olive (Osmanthus fragrans), one of the top ten traditional flowers in China, has been cultivated for more than two thousand years. However, in recent years, an increasing number of O. fragrans cultivars with colored leaves have been cultivated for their ornamental value. To study the molecular mechanism underlying the observed changes in leaf color, we selected O. fragrans ‘Yinbi Shuanghui’ (Y), which has yellow-white leaves, and O. fragrans ‘Sijigui’ (S), which has green leaves, as materials. Pigment content measurement showed that the chlorophyll, carotenoid and anthocyanin contents in Y were lower than in S. According to the SWATH-MS sequencing results, a total of 3,959 proteins were quantitatively identified, 1,300 of which were differentially expressed proteins (DEPs), including 782 up-regulated and 518 down-regulated proteins in Y compared to S. Functional enrichment analysis of DEPs revealed that down-regulated expression of photosynthesis related proteins may lead to the inhibition of chlorophyll synthesis in Y, this may be the main cause of leaf color change. Moreover, a protein interaction prediction model also showed that proteins such as PetC, PsbO, PsbP, and PsbQ were key proteins in the interaction network, and the up-regulated proteins participating in the anthocyanin and carotenoid pathways may be related to the formation of yellow-white leaves. Taken together, our findings represent the first SWATH-MS-based proteomic report on colored leaf O. fragrans and reveal that chlorophyll synthesis and secondary metabolism pathways contribute to the changes in leaf color.

Biological and Molecular Characterization of the Cucumber Mosaic Virus Infecting Purple Coneflowers in China

Purple coneflower (Echinacea purpurea L.), which is a perennial herbaceous plant belonging to the Asteraceae family, is extensively cultivated because of its medicinal applications. However, in Hohhot, Inner Mongolia, China, purple coneflowers in the field exhibited symptoms such as mottle, mosaic, and crinkle. This study aimed to explore the biological and molecular characteristics of the cucumber mosaic virus (CMV) infecting the purple coneflowers in China. We observed isometric particles approximately 30 nm in diameter in the symptomatic leaf specimens. Infection with the CMV was confirmed via high-throughput sequencing and RT-PCR validation. Mechanical inoculation assays demonstrated that the CMV-SGJ isolate could infect both Nicotiana benthamiana and Nicotiana tabacum. Three viral genomic components were identified: RNA1 with 3321 nucleotides, RNA2 with 3048 nucleotides, and RNA3 with 2209 nucleotides. Phylogenetic analysis revealed that the CMV-SGJ isolate clustered into phylogenetic subgroup IA, exhibiting a nucleotide identity of 92.2–95% with subgroup IA CMV isolates in GenBank. This report is the first documentation of the complete genome of the CMV infecting purple flowers in China.

Functional Characterization of PoEP1 in Regulating the Flowering Stage of Tree Peony.

The tree peony, a traditional flower in China, has a short and concentrated flowering period, restricting the development of the tree peony industry. To explore the molecular mechanism of tree peony flowering-stage regulation, PoEP1, which regulated the flowering period, was identified and cloned based on the transcriptome and degradome data of the early-flowering mutant Paeonia ostii 'Fengdan' (MU) and Paeonia ostii 'Fengdan' (FD). Through bioinformatics analysis, expression pattern analysis, and transgene function verification, the role of PoEP1 in the regulation of tree peony flowering was explored. The open-reading frame of PoEP1 is 1161 bp, encoding 386 amino acids, containing two conserved domains. PoEP1 was homologous to the EP1 of other species. Subcellular localization results showed that the protein was localized in the cell wall and that PoEP1 expression was highest in the initial decay stage of the tree peony. The overexpression of PoEP1 in transgenic plants advanced and shortened the flowering time, indicating that PoEP1 overexpression promotes flowering and senescence and shorten the flowering time of plants. The results of this study provide a theoretical basis for exploring the role of PoEP1 in the regulation of tree peony flowering.

Lonicera japonica Thunb. and its characteristic component chlorogenic acid alleviated experimental colitis by promoting Lactobacillus and fecal short‐chain fatty acids production

AbstractUlcerative colitis is intricately linked to intestinal oxidative stress and dysbiosis of the gut microbiota. Lonicera japonica Thunb. (LJ) is a traditional edible and medical flower in China, and chlorogenic acid (CGA) is one of its characteristic components. However, it remains unclear whether gut microbiota plays a role in the therapeutic effects of LJ and GCA on colitis. Here, we first observed that oral administration of LJ and CGA for 3 weeks dramatically promoted the growth of Lactobacillus and fecal short‐chain fatty acids (SCFAs) production in healthy mice. Subsequently, the alleviating effects of LJ and CGA on colitis were explored with a dextran sulfate sodium‐induced colitis mice model. The intervention of LJ and CGA notably alleviated inflammation, intestinal barrier impairment, and oxidative stress in colitis and led to a significant elevation in Lactobacillus and fecal SCFAs. Eventually, the key role of gut microbiota and their metabolites on the therapeutic effects was validated by performing fecal microbiota transplantation and sterile fecal suspensions transplantation from LJ and CGA‐treated healthy mice to colitis mice. Our findings demonstrated that consumption of LJ and CGA could benefit the host both in healthy condition and colitis. The beneficial effects were attributed to the improvement of the endogenous antioxidant system and promotion of the probiotic Lactobacillus and SCFAs production. Our study highlighted the great potential of LJ and CGA to be consumed as functional foods and provided novel mechanisms by which they alleviated colitis.

Optimizing DUS testing for Chimonanthus praecox using feature selection based on a genetic algorithm.

Chimonanthus praecox is a famous traditional flower in China with high ornamental value. It has numerous varieties, yet its classification is highly disorganized. The distinctness, uniformity, and stability (DUS) test enables the classification and nomenclature of various species; thus, it can be used to classify the Chimonanthus varieties. In this study, flower traits were quantified using an automatic system based on pattern recognition instead of traditional manual measurement to improve the efficiency of DUS testing. A total of 42 features were quantified, including 28 features in the DUS guidelines and 14 new features proposed in this study. Eight algorithms were used to classify wintersweet, and the random forest (RF) algorithm performed the best when all features were used. The classification accuracy of the outer perianth was the highest when the features of the different parts were used for classification. A genetic algorithm was used as the feature selection algorithm to select a set of 22 reduced core features and improve the accuracy and efficiency of the classification. Using the core feature set, the classification accuracy of the RF model improved to 99.13%. Finally, K-means was used to construct a pedigree cluster tree of 23 varieties of wintersweet; evidently, wintersweet was clustered into a single class, which can be the basis for further study of genetic relationships among varieties. This study provides a novel method for DUS detection, variety identification, and pedigree analysis.

Research progress of Chinese rose breeding techniques

Chinese rose is one of the top ten most famous traditional flowers in China, as well as one of the world's four cut flowers and the most frequently used ornamental flower, known as the "queen of flowers." According to the records of the American Rose Association, in 2000 there were more than 24,000 varieties of Chinese roses worldwide. In China, the Chinese rose has a lengthy history of cultivation, a strong mass base, a positive moral symbol, and a robust group of varieties. In recent years, an increasing number of plant breeders have been devoted to the study of Chinese rose breeding, and Chinese rose breeding techniques have advanced by leaps and bounds and produced fruitful outcomes. This paper summarized the breeding objectives of contemporary Chinese rose, analyzed and discussed the breeding techniques of molecular breeding, introduction and screening, crossbreeding, bud sport breeding, mutation breeding, and so on, and anticipated the future research field of Chinese rose breeding.

Research advance on cold tolerance in chrysanthemum.

Chrysanthemums are one of the top ten most well-known traditional famous flowers in China and one of the top four cut flowers worldwide, holding a significant position in landscape gardening. The cold temperatures of winter restrict the cultivation, introduction, and application of chrysanthemum, resulting in high costs for year-round production. This severely impacts the ornamental and economic value of chrysanthemum. Therefore, research on cold tolerance is of vital importance for guiding chrysanthemum production and application. With the development of genomics, transcriptomics, metabolomics, and other omics approaches, along with high-throughput molecular marker technologies, research on chrysanthemum cold tolerance has been continuously advancing. This article provides a comprehensive overview of the progress in cold tolerance research from various aspects, including chrysanthemum phenotype, physiological mechanisms, the forward genetics, molecular mechanisms, and breeding. The aim is to offer insights into the mechanisms of cold tolerance in chrysanthemum and provide reference for in-depth research and the development of new cold tolerance chrysanthemum varieties.

Presenting the Secrets: Exploring Endogenous Defense Mechanisms in Chrysanthemums against Aphids

As the second-largest cut flower plant globally and one of the top ten traditional flowers in China, chrysanthemums hold significant economic value, encompassing both ornamental and medicinal applications. However, aphids pose a considerable threat as one of the most critical pests affecting chrysanthemums. These pests not only diminish the ornamental value of chrysanthemums through feeding and reproduction but also transmit numerous plant viruses, causing irreversible damage. This review examines aphids’ feeding and damage patterns as a starting point, highlighting the unique endogenous defense mechanisms that have evolved in chrysanthemums during their continuous struggle against aphids. These mechanisms include constitutive defense and induced defense. In addition, we enumerate aphid-resistance genes that have been reported in chrysanthemums. Furthermore, this paper compares and predicts the aphid-resistance genes of other species based on the published Chrysanthemum nankingense genome, aiming to provide a valuable reference for future research on aphid-resistance genes in chrysanthemums.

Recent Advances in Flower Color and Fragrance of Osmanthus fragrans

Osmanthus fragrans is an evergreen shrub or tree of the Oleaceae family with a long history of cultivation in Asian countries and is one of the ten traditionally famous flowers in China, with important cultural and economic value. The unique floral color and fragrance of O. fragrans are formed by a variety of endogenous metabolites that distinguish it from other flowers and exhibit extraordinary ornamental value. However, many studies on the flower color and fragrance of this plant have been mainly based on bioactive extracts and physiological characteristics, leading to a notable lack of molecular machinery and systematic research. In this review, recent advances in bioactive ingredients associated with the underlying regulatory mechanisms, as well as the prospect for industrial utilization, are comprehensively presented and critically evaluated. In particular, the isolated components and essential genes required for flower color and fragrance are also well summarized, which will provide a scientific basis for molecular breeding for ornamental applications and facilitate the discovery of novel natural products for the future industrial development of O. fragrans. In prospect, we plan to use genetic research and high-throughput omics to analyze the genes related to the flower color and fragrance of O. fragrans, and at the same time, we will hybridize and breed excellent O. fragrans varieties that are resistant to low temperature.

Pseudocercospora rhododendricola Causing Leaf dark Spot on Rhododendron pulchrum by the first phylogenetic analyses.

Rhododendron pulchrum Sweet is a famous ornamental flower in China. In December 2020, a leaf spot disease was observed on cv. Maojuan in Zhanjiang (21.17 N, 110.18 E), Guangdong, China. The spots were irregular and distributed on both sides of the main vein. They were dark to black, and their borders were obvious. The coalescence of the spots eventually led to leaf wilt. The disease incidence was 100% (n = 100, about 50 ha ). Thirty infected leaves were collected from the field, and the margin of the diseased tissues was cut into 2 mm × 2 mm pieces. Samples were surface disinfected with 75% ethanol and 2% sodium hypochlorite for 30 and 60 s, respectively. They were rinsed thrice with sterile water before isolation. The tissues were plated on potato dextrose agar (PDA) medium and incubated at 28 ℃. After 5 days, fungal colonies appeared on the PDA. Pure cultures were produced by transferring hyphal tips to new PDA plates. Three isolates(RSP-1, RSP-2, and RSP-3) were obtained and the colonies of isolates were preserved in glycerol (15%) at -80 °C deposited at the Museum of Guangdong Ocean University. The morphology of these three isolates was consistent, and their sequences showed 100% homology according to ITS, TEF1, and ACT analysis results. The colonies grew to approximately 5 cm in diameter after 10 days. They showed olive green with off-white aerial mycelia. Stromata and conidia were observed on leaf lesions. Stromata were olivaceous brown. Conidia were solitary, cylindrical to narrowly obclavate, mildly curved, obtuse to rounded at the apex, and 1- to 3-septate; they had dimensions of 20 to 60 × 2.0 to 3.0 μm (n= 30). These morphological characteristics were not different from the description of Pseudocercospora rhododendricola (J.M. Yen) Deighton (Liu et al. 1998). For molecular identification, the colony PCR method with MightyAmp DNA Polymerase (Takara-Bio, Dalian, China) (Lu et al. 2012) was used to amplify the internal transcribed spacer (ITS), translation elongation factor 1-α gene (TEF1), and actin (ACT) loci of the isolates using primer pairs ITS4/ITS5, EF1/EF2, and ACT-512F/ACT-783R, respectively (White et al., 1990; O'Donnell et al. 1997). The sequences of the isolateRSP-1 were deposited in the GenBank (ITS, MW629798; TEF1, MW654168; and ACT, MW654170). BLAST analysis showed that the sequences of P. rhododendricola were submitted to GenBank for the first time by the author of this paper. A phylogenetic tree was generated based on the concatenated data of ITS, TEF1, and ACT sequences from GenBank by the Maximum Likelihood method. The isolates were closest to Pseudocercospora sp. CPC 14711 (Crous et al., 2013). Phylogenetic and morphological analyses identified the isolates as P. rhododendricola. Pathogenicity tests were conducted in a greenhouse at 24°C-30℃ with 80% relative humidity. Healthy cv. Maojuan were grown in pots. Unwounded leaflets were inoculated with 5 mm-diameter mycelial plugs of the isolates or agar plugs (as control) (5 leaflets per plant, 3 plants, 2-month-old plants). The test was performed thrice. Disease symptoms were found on the leaves after 2 weeks, whereas the control plants remained healthy. The fungus was re-isolated from the infected leaves and confirmed as the same isolatesby morphological and ITS analyses. P. rhododendricola was the cause of leaf spot of Rhododendron sp. from Singapore (Liu et al., 1998). For the first time, this pathogen was identified by combining phylogenetic and morphological analyses. The sequences in this study would be used as the reference sequences for further studies.

First Report of Athelia rolfsii Causing Stem Rot on Sunflower (Helianthus annuus L.) in Sichuan, China.

Sunflower (Helianthus annuus L.) is a major oilseed crop in the world, but recently it has become a popular ornamental flower in China (Kaya ET AL., 2012). Notably, stem rot was frequently observed on 30-day-old sunflower plants in Sichuan Province, P. R. China. In May 2021, 207 plants with stem rot and premature death were found among the investigated 1732 plants, with 11.95% incidence rate. Stem rot were mainly observed on the base stem of plants. Infected stems developed brown lesions that became slightly sunken and covered with white mycelial mats. With disease progress, the affected plants eventually wilted at early stage (Fig. 1A). For pathogen isolation, mycelia were harvested directly from diseased tissue and cultured on potato dextrose agar (PDA) at 25±2℃ in incubator without light. Eighteen fungal isolates with similar colony morphology were consistently isolated by purifying from different sampling areas. These isolates would form radial colonies with white aerial mycelia possessing branches and septa, and some could form clamp connection structure on PDA. Their average growth rate was 27.6 ± 0.09 mm per day (Fig. 1B & C). White granular sclerotia were abundantly produced on 6-day-old colonies. The sclerotia with a diameter of 1.18 ± 0.26 mm (n=348) gradually changed from white to light yellow and finally to brown with age (Fig. 1B). A representative isolate NCSF5.20-8 was identified accurately by multi-locus approach, and its genomic DNA was extracted for amplifying and sequencing the fragments of ITS, 18 S and TEF1-α according to previous description (Zhong et al., 2021). The nucleotide BLAST search of these sequences was nearly 100% identical to Athelia rolfsii (the teleomorph of Sclerotium rolfsii Sacc.) with accession number MN258360.1 (499/499 bp, 100%), AY665774.1 (1428/1428 bp, 100%), and JF267794.1 (489/490, 99%), respectively. The obtained sequences were deposited in GenBank with accession number OK635580.1, OM319631.1 and OK665849.1. Phylogenetic analysis based on simultaneously available ITS, 18S and TEF1-α sequences of Athelia genus indicated that NCSF5.20-8 could be clustered into the A. rolfsii clade with a support value of 100% (Fig. 2). Combining the above morphological characteristics and molecular identification, the isolate NCSF5.20-8 was finally confirmed as the identity of A. rolfsii (Mordue 1974; Zhong et al., 2021). In order to fulfil Koch's postulates and prove the pathogenicity of NCSF5.20-8 to sunflower, mycelial plugs were leaned on the base stem of healthy sunflower plants (cv. Guangwu muntain) with 45-day-old, while plants with same growth treated by PDA plug free of mycelium were used as control. All the inoculated plants were kept in a greenhouse at 25±2°C with 14 h photoperiod and 80% relative humidity. The experiments were conducted for triple biological repeats. Two days after inoculation, all the plants inoculated with NCSF5.20-8 had typical symptoms of stem rot, whereas, the control plants remained asymptomatic (Fig. 1D). Using above mentioned protocol, A. rolfsii was re-isolated only from the symptomatic stem of inoculated plants. To our knowledge, stem rot caused by A. rolfsii on sunflower has been reported in Italy and Turkey (Infantino et al., 1997; Cer & Morca, 2020), but it is the first report in China. For this pathogen has a wide host range with serious destructiveness (Punja, 1985), our research is beneficial to develop strategies to mitigate future losses of sunflower in China.

Comparative analysis of the chrysanthemum transcriptome with DNA methylation inhibitors treatment and silencing MET1 lines

BackgroundAs one of the ten most famous flowers in China, the chrysanthemum has rich germplasm with a variety of flowering induction pathways, most of which are photoperiod-induced. After treatment with DNA methylation inhibitors, it was found that DNA methylation plays an important role in flowering regulation, but the mechanism of action remains unclear. Therefore, in this study, curcumin, 5-azaC, their mixed treatment, and MET1-RNAi lines were used for transcriptome sequencing to find out how different treatments affected gene expression in chrysanthemums at different stages of flowering.ResultsGenomic DNA methylation levels were measured using HPLC technology. The methylation level of the whole genome in the vegetative growth stage was higher than that in the flowering stage. The methylation level of DNA in the vegetative growth stage was the lowest in the curcumin and mixed treatment, and the methylation level of DNA in the transgenic line, mixed treatment, and curcumin treatment was the lowest in the flowering stage. The flowering rate of mixed treatment and curcumin treatment was the lowest. Analysis of differentially expressed genes in transcriptomes showed that 5-azaC treatment had the most differentially expressed genes, followed by curcumin and transgenic lines, and mixed treatment had the fewest. In addition, 5-azaC treatment resulted in the differential expression of multiple DNA methylation transferases, which led to the differential expression of many genes. Analysis of differentially expressed genes in different treatments revealed that different treatments had gene specificity. However, the down-regulated GO pathway in all 4 treatments was involved in the negative regulation of the reproductive process, and post-embryonic development, and regulation of flower development. Several genes associated with DNA methylation and flowering regulation showed differential expression in response to various treatments.ConclusionsBoth DNA methylase reagent treatment and targeted silencing of the MET1 gene can cause differential expression of the genes. The operation of the exogenous application is simple, but the affected genes are exceedingly diverse and untargeted. Therefore, it is possible to construct populations with DNA methylation phenotypic diversity and to screen genes for DNA methylation regulation.

PlMAPK1 facilitates growth and photosynthesis of herbaceous peony (Paeonia lactiflora Pall.) under high-temperature stress

Herbaceous peony (Paeonia lactiflora Pall.) is a traditional famous flower in China that prefers cold climates and is not tolerant of high summer temperatures. Mitogen-activated protein kinase (MAPK) is widely involved in plant signal transduction to various environmental stresses. In order to clarify the role of PlMAPK1 in response to high-temperature stress, it was cloned, and its open reading frame was 1215 bp, encoding 405 amino acids. Quantitative real-time PCR (qRT-PCR) analysis showed that when the plant was severely damaged by high temperatures, the expression level of PlMAPK1 was at its peak. Moreover, based on a systematic study of exogenous yeast, it was found that the yeast strain overexpressing PlMAPK1 grew better than the control under high-temperature stress. In addition, PlMAPK1 was transiently silenced by virus induced gene silencing technology (VIGS) in P. lactiflora. And under high-temperature stress, the leaves of transgenic plants wilted significantly, the accumulation of reactive oxygen species increased and the photosynthetic capacity decreased significantly. These findings suggested that PlMAPK1 might play a positive regulatory role in the response of P. lactiflora to high-temperature stress, laying a theoretical groundwork for P. lactiflora high-temperature tolerance breeding.

Genome-wide association study of 23 flowering phenology traits and 4 floral agronomic traits in tree peony (Paeonia section Moutan DC.) reveals five genes known to regulate flowering time.

Tree peony is a unique traditional flower in China, with large, fragrant, and colorful flowers. However, a relatively short and concentrated flowering period limits the applications and production of tree peony. A genome-wide association study (GWAS) was conducted to accelerate molecular breeding for the improvement of flowering phenology traits and ornamental phenotypes in tree peony. A diverse panel of 451 tree peony accessions was phenotyped for 23 flowering phenology traits and 4 floral agronomic traits over 3 years. Genotyping by sequencing (GBS) was used to obtain a large number of genome-wide single-nucleotide polymorphisms (SNPs) (107 050) for the panel genotypes, and 1047 candidate genes were identified by association mapping. Eighty-two related genes were observed during at least 2 years for flowering, and seven SNPs repeatedly identified for multiple flowering phenology traits over multiple years were highly significantly associated with five genes known to regulate flowering time. We validated the temporal expression profiles of these candidate genes and highlighted their possible roles in the regulation of flower bud differentiation and flowering time in tree peony. This study shows that GWAS based on GBS can be used to identify the genetic determinants of complex traits in tree peony. The results expand our understanding of flowering time control in perennial woody plants. Identification of markers closely related to these flowering phenology traits can be used in tree peony breeding programs for important agronomic traits.

Characteristics of PoVIN3, a Key Gene of Vernalization Pathway, Affects Flowering Time.

The tree peony (Paeonia section Moutan DC.) is the candidate flower in China, with abundant germplasm resources and high ornamental value. However, the short and concentrated flowering period severely restricted the improvement of the economic value of tree peonies. Based on the full-length transcriptome database of tree peonies, the PoVIN3 (GenBank ID: OP341879), involved in the flowering regulation of tree peonies were identified and cloned for the first time. The PoVIN3 was also characterized by bioinformatics methods, quantitative real-time PCR (qRT-PCR), and the establishment of a transgenic system. The expression levels of PoVIN3 in seven different petals developmental stages were the highest at the initial flowering stage of the variant cultivar of Paeonia ostii 'Fengdan,' the initial decay stage of the normal flowering Paeonia ostii 'Fengdan,' and the half opening stage of the late flowering Paeonia suffruticosa 'Lianhe.' Tissue-specific expression analysis showed that the relative expression levels of PoVIN3 were the highest in sepals of both normal flowering Paeonia ostii 'Fengdan' and the late flowering Paeonia suffruticosa 'Lianhe,' and the highest expression was in stamens of early flowering mutant Paeonia ostii 'Fengdan.' In addition, the flowering time of pCAMBIA2300-PoVIN3 transgenic plants was significantly earlier than that of the wild-type, indicating that PoVIN3 could promote plant flowering. The results provide a theoretical basis for exploring the role of PoVIN3 in the regulation of flowering in tree peonies.

Comprehensive Genomic Survey, Structural Classification, and Expression Analysis of WRKY Transcription Factor Family in Rhododendron simsii

(1) Rhododendron is one of the top ten traditional flowers in China, with both high ornamental and economic values. However, with the change of the environment, Rhododendron suffers from various biological stresses. The WRKY transcription factor is a member of the most crucial transcription factor families, which plays an essential regulatory role in a variety of physiological processes and developmental stresses. (2) In this study, 57 RsWRKYs were identified using genome data and found to be randomly distributed on 13 chromosomes. Based on gene structure and phylogenetic relationships, 57 proteins were divided into three groups: I, II, and III. Multiple alignments of RsWRKYs with Arabidopsis thaliana homologous genes revealed that WRKY domains in different groups had different conserved sites. RsWRKYs have a highly conserved domain, WRKYGQK, with three variants, WRKYGKK, WRKYGEK, and WRKYGRK. Furthermore, cis-acting elements analysis revealed that all of the RsWRKYs had stress and plant hormone cis-elements, with figures varying by group. Finally, the expression patterns of nine WRKY genes treated with gibberellin acid (GA), methyl jasmonate (MeJA), heat, and drought in Rhododendron were also measured using quantitative real-time PCR (qRT-PCR). The results showed that the expression levels of the majority of RsWRKY genes changed in response to multiple phytohormones and abiotic stressors. (3) This current study establishes a theoretical basis for future studies on the response of RsWRKY transcription factors to various hormone and abiotic stresses as well as a significant foundation for the breeding of new stress-tolerant Rhododendron varieties.

Preliminary Research on the Effects of Different Substrates on the Metabolome of Potted Peonies

Peony (Paeonia suffruticosa Andr.) is a traditional ornamental flower in China. Peony potted culture has become mainstream. The development of agricultural and forestry waste instead of a nonrenewable peat matrix as the substrate is an important direction for the future industry of potted peonies. However, the mechanism of the effects of different substrates on the growth and development of peonies remains unclear. In this experiment, “Luhehong”, a peony variety from Heze, Shandong Province, was selected as the main experimental material. The response mechanism of peony roots to different substrate proportions was analyzed using untargeted metabolomics of potted peonies. Results showed that the potential for pot growth of planted peonies using the mixed-straw mixing matrix (Matrix K) is better than that of the rice husk matrix (Matrix G) and the control matrix. Moreover, the comparative analysis of the metabolic groups indicates that the number of peony root secretions in the three matrices has a remarkable difference, possibly related to the nutrition supply levels of the peony roots, in the different matrices of adaptive response and adjustment. Furthermore, (2r)-3-hydroxyisovaleroylcarnitine, trigonelline, 2-acetylresorcinol, and dehydroascorbic acid (oxidized vitamin C)—four metabolites with the most substantial intergroup differences—are considered key metabolites. The metabolic pathway analysis of propanoate, and ascorbate and aldarate metabolism, and the two pathways related to an environmental response, namely, ABC transporters and phosphatidylinositol signaling system, indicated that these pathways were remarkably enriched. Both may be the key way to affect the growth and development of potted peonies. This study can provide an important reference for the rational allocation of the substrate of agricultural and forestry waste in potted peony cultivation and application.

Air Layering Improves Rooting in Tree Peony Cultivars from the Jiangnan Group

Tree peony (Paeonia suffruticosa Andr.), a unique traditional flower in China, is famous for its ornamental value, medical use, and edible oil production. Traditional propagation methods, such as sowing, dividing, and grafting do not allow the large-scale production of selected peony varieties. Therefore, the objective of our study is to evaluate an air-layering technique on the rooting success of three tree peony cultivars (‘Baoqing Hong’, ‘Quehao’, and ‘Xishi’). The experiments were established through consideration of the influence of the time of the year the rooting was performed (mid-May, mid-June, or mid-July) and the growth regulators (1-naphthaleneacetic acid-NAA and indole-3-butyric acid-IBA) applied at different concentrations (1000 mg/L, 1500 mg/L, 2000 mg/L). The results showed that the rooting rate was the highest when the air-layering time occurred in mid-June, and the rooting rate of ‘Quehao’ was found to be the most significant, reaching 100%. The rooting percentages of 82.86% and 77.14% were obtained for ‘Baoqing Hong’ and ‘Xishi’, respectively. The growth regulators affected the rooting performance of the three cultivars differently. The rooting parameters of ‘Quehao’ were negatively correlated with the concentration of NAA but positively correlated with IBA, whereas the ‘Baoqing Hong’ and ‘Xishi’ cultivars showed no dose dependence for the supplied growth regulators. Root number, root tip number, and maximum root length in ‘Quehao’ were higher than those of the other two cultivars. The conclusion of our study is that the air-layering technique is a suitable method for achieving satisfactory propagation of selected tree peony cultivars.

Proteomic Analysis of the Inflorescence Stem Mechanical Strength Difference in Herbaceous Peonies (Paeonia lactiflora Pall.).

The herbaceous peony (Paeonia lactiflora Pall.) is a traditional rare flower in China, and production of its cut flowers has developed gradually in many places of the world. However, the inflorescence stems of some P. lactiflora cultivars have such low mechanical strength that the cut flower production was severely restricted. To better understand the causes of this problem from a protein expression level, two P. lactiflora cultivars with different inflorescence stem mechanical strengths were analyzed by two-dimensional electrophoresis and MALDI-TOF/MS. More than 1700 clear protein spots were detected, 53 of which varied significantly. Moreover, 23 of the differentially expressed proteins were identified and confirmed and are involved in various biological processes such as metabolism, protein biosynthesis and transport, signal transduction, and defensive response. Especially, cinnamyl alcohol dehydrogenase (CAD) and xyloglucan endotransglucosylase/hydrolase (XTH) were strongly connected to the inflorescence stem mechanical strength in P. lactiflora.

Cloning and Functional Analysis of NtMYB9 in ‘Jinzhanyintai’ of Narcissus tazetta var. chinensis

Narcissus tazetta var. chinensis M.Roem. (Chinese Narcissus) is a traditional and famous flower in China, and its corona shows a transition from green to yellow with the opening of flowers, which is of great ornamental value. To investigate the molecular mechanism of the corona color-forming in the Chinese Narcissus, in this study, a MYB gene was screened from the transcriptome of the corona by bioinformatics analysis methods, named NtMYB9. The expression level of the NtMYB9 gene was significantly higher in the corona than in the tepal, filament, ovary and leaf, and reached the highest level at the fourth period of complete coloration of the corona. The full-length sequence of the NtMYB9 coding region was cloned using the corona cDNA as a template. Sequence analysis revealed that NtMYB9 protein contained R2 and R3 domains, phylogenetic tree analysis showed that the NtMYB9 protein was most closely related to flavonol activators. Subcellular localization showed that NtMYB9 was localized in the nucleus. The overexpression of NtMYB9 gene into tobacco leaves and the expression level of seven enzyme genes related to the flavonoid biosynthesis pathway were significantly up-regulated. The transient transformation of Petunia × hybrida (Petunia) and Phalaenopsis aphrodite (Phalaenopsis) significantly revealed that the NtMYB9 gene could turn flowers yellow. These results suggest that the NtMYB9 gene is involved in the positive regulation of flavonoid biosynthesis in the Chinese Narcissus and may promote the synthesis of flavonols. In conclusion, these findings provide a valuable resource for further studies on the regulatory mechanism of the flavonoid biosynthesis pathway, and they are also beneficial to the molecular breeding of Chinese Narcissus.