Factors affecting quantity of pollen dispersal of spray cut chrysanthemum (Chrysanthemum morifolium)

Potential Allergenicity of Plants Used in Allergological Communication: An Untapped Tool for Prevention

Plants are often used to illustrate allergy-related medical products, services, patient information materials and news. The illustration of allergenic plants is an important tool in patient education, contributing to the prevention of pollinosis, as patients can recognize plants and avoid pollen exposure. In this study, it is aimed to evaluate the pictorial content of allergy-related websites depicting plants. A total of 562 different photographs depicting plants were collected using image search, identified and categorized according to their potential allergenicity. Of the total 124 plant taxa, 25% of plants were identified to the genus level and a further 68% were identified to the species level. Plants with low allergenicity were found in 85.4% of the pictures, while plants of high allergenicity were shown in only 4.5% of the pictorial information. Brassica napus was the most frequent species identified (8.9% of the overall identified plants), while blooming Prunoidae, Chrysanthemum spp. and Taraxacum officinale were also common. Considering both allergological and design aspects, some plant species have been proposed for more professional and responsible advertising. The internet has the potential to provide visual support for patient education in allergenic plants, but emphasis must be put on the transmission of the correct visual message.

DgMYB2 improves cold resistance in chrysanthemum by directly targeting DgGPX1

MYB transcription factors play important roles in plant responses to cold stress, but the associated underlying mechanisms remain unclear. In this study, a cold-induced MYB transcription factor, DgMYB2, was isolated from chrysanthemum (Chrysanthemum morifolium Ramat). DgMYB2 was localized to the nucleus and exhibited transactivational activity. Overexpression of DgMYB2 improved cold tolerance in chrysanthemum, while cold tolerance in the antisense suppression lines decreased compared to that of the wild type. Additionally, electrophoretic mobility shift assays, chromatin immunoprecipitation, luciferase complementary imaging analysis, and dual-luciferase reporter gene detection experiments confirmed that DgMYB2 directly targets DgGPX1 and increases the activity of glutathione peroxidase to reduce the accumulation of reactive oxygen species, thereby improving cold resistance in chrysanthemum.

Chrysanthemum embryo development is negatively affected by a novel ERF transcription factor, CmERF12

Embryo abortion often occurs during distant hybridization events. Apetala 2/ethylene-responsive factor (AP2/ERF) proteins are key transcription factor (TF) regulators of plant development and stress resistance, but their roles in hybrid embryo development are poorly understood. In this study, we isolated a novel AP2/ERF TF, CmERF12, from chrysanthemum and show that it adversely affects embryo development during distant hybridization. Transcriptome and real-time quantitative PCR demonstrate that CmERF12 is expressed at significantly higher levels in aborted ovaries compared with normal ones. CmERF12 localizes to the cell nucleus and contains a conserved EAR motif that mediates its transcription repressor function in yeast and plant cells. We generated artificial microRNA (amiR) CmERF12 transgenic lines of Chrysanthemum morifolium var. 'Yuhualuoying' and conducted distant hybridization with the wild-type tetraploid, Chrysanthemum nankingense, and found that CmERF12-knock down significantly promoted embryo development and increased the seed-setting rates during hybridization. The expression of various genes related to embryo development was up-regulated in developing ovaries from the cross between female amiR-CmERF12 C. morifolium var. 'Yuhualuoying'× male C. nankingense. Furthermore, CmERF12 directly interacted with CmSUF4, which is known to affect flower development and embryogenesis, and significantly reduced its ability to activate its target gene CmEC1 (EGG CELL1). Our study provides a novel method to overcome barriers to distant hybridization in plants and reveals the mechanism by which CmERF12 negatively affects chrysanthemum embryo development.

A Novel Lateral Organ Boundary-domain Factor CmLBD2 Positively Regulates Pollen Development by Activating CmACOS5 in Chrysanthemum morifolium

Male sterility, as a common reproductive characteristic in plants, plays an important role in breeding, in which pollen abortion is a key factor leading to male sterility. Here, based on a low expression level gene CmACOS5 in transcriptome of pollen abortive chrysanthemum, a new transcription factor CmLBD2 of the Lateral Organ Boundaries Domain family, which could bind the promoter of CmACOS5 by yeast one-hybrid library was screened. This study revealed the origin and expression pattern of CmLBD2 in chrysanthemum and verified the functions of two genes in pollen development by transgenic means. Inhibiting the expression of CmACOS5 or CmLBD2 can lead to a large reduction in pollen and even abortion in chrysanthemum. Using yeast one-/two-hybrid, electrophoretic mobility shift assays, and luciferase reporter assays, it was verified that CmLBD2 directly binds to the promoter of CmACOS5. These results suggest that LBD2 is a novel, key transcription factor regulating pollen development. This result will provide a new research background for enriching the function of LBD family proteins and also lay a new foundation for the breeding of male sterile lines and the mechanism of pollen development.

Characteristic Volatile Fingerprints of Four Chrysanthemum Teas Determined by HS-GC-IMS

Volatile composition is an important feature that determines flavor, which actively affects the overall evaluation of chrysanthemum tea. In this study, HS-GC-IMS (headspace-gas chromatography-ion mobility spectrometry) was performed to characterize the volatile profiles of different chrysanthemum tea subtypes. Forty-seven volatiles of diverse chemical nature were identified and quantified. Partial least squares discriminant analysis (PLS-DA) revealed that four chrysanthemum teas were distinct from each other based on their volatile compounds. Furthermore, this work provides reference methods for detecting novel volatile organic compounds in chrysanthemum tea plants and products.

Experimental quantification of pollen with DNA metabarcoding using ITS1 and trnL

Although the use of metabarcoding to identify taxa in DNA mixtures is widely approved, its reliability in quantifying taxon abundance is still the subject of debate. In this study we investigated the relationships between the amount of pollen grains in mock solutions and the abundance of high-throughput sequence reads and how the relationship was affected by the pollen counting methodology, the number of PCR cycles, the type of markers and plant species whose pollen grains have different characteristics. We found a significant positive relationship between the number of DNA sequences and the number of pollen grains in the mock solutions. However, better relationships were obtained with light microscopy as a pollen grain counting method compared with flow cytometry, with the chloroplastic trnL marker compared with ribosomal ITS1 and with 30 when compared with 25 or 35 PCR cycles. We provide a list of recommendations to improve pollen quantification.

Transcriptome Profiling Unravels a Vital Role of Pectin and Pectinase in Anther Dehiscence in Chrysanthemum

Chrysanthemum (Chrysanthemum morifolium (Ramat.) Kitamura) plants have great ornamental value, but their flowers can also be a source of pollen contamination. Previously, morphological and cytological studies have shown that anthers of some chrysanthemum cultivars such as 'Qx-115' fail to dehisce, although the underlying mechanism is largely unknown. In this study, we investigated the molecular basis of anther indehiscence in chrysanthemum via transcriptome analysis of a dehiscent cultivar ('Qx-097') and an indehiscent cultivar ('Qx-115'). We also measured related physiological indicators during and preceding the period of anther dehiscence. Our results showed a difference in pectinase accumulation and activity between the two cultivars during dehiscence. Detection of de-esterified pectin and highly esterified pectin in anthers during the period preceding anther dehiscence using LM19 and LM20 monoclonal antibodies showed that both forms of pectin were absent in the stomium region of 'Qx-097' anthers but were abundant in that of 'Qx-115' anthers. Analysis of transcriptome data revealed a significant difference in the expression levels of two transcription factor-encoding genes, CmLOB27 and CmERF72, between 'Qx-097' and 'Qx-115' during anther development. Transient overexpression of CmLOB27 and CmERF72 separately in tobacco leaves promoted pectinase biosynthesis. We conclude that CmLOB27 and CmERF72 are involved in the synthesis of pectinase, which promotes the degradation of pectin. Our results lay a foundation for further investigation of the role of CmLOB27 and CmERF72 transcription factors in the process of anther dehiscence in chrysanthemum.

Comparative Analysis of Phytochemical Composition of Gamma-Irradiated Mutant Cultivars of Chrysanthemum morifolium

The flowers of chrysanthemum species are used as a herbal tea and in traditional medicine. In addition, members of the genus have been selected to develop horticultural cultivars of diverse floral colors and capitulum forms. In this research, we investigated the phytochemical composition of eight gamma-irradiation mutant cultivars of Chrysanthemum morifolium and their original cultivars. The mutant chrysanthemum cultivars were generated by treatment with various doses of ⁶⁰Co gamma irradiation of stem cuttings of three commercial chrysanthemum cultivars as follows: ‘ARTI-Dark Chocolate’ (50Gy), ‘ARTI-Purple Lady’ (30 Gy), and ‘ARTI-Yellow Star’ (50 Gy) derived from ‘Noble Wine’; ‘ARTI-Red Star’ (50 Gy) and ‘ARTI-Rising Sun’ (30 Gy) from ‘Pinky’; ‘ARTI-Purple’ (40 Gy) and ‘ARTI-Queen’ (30 Gy) from ‘Argus’; and ‘ARTI-Rollypop’ (70 Gy) from ‘Plaisir d’amour’. Quantitative analysis of flavonoids, phenolic acids, anthocyanins, and carotenoids in the flowers of the 12 chrysanthemum cultivars was performed using high performance liquid chromatography-diode array detector-electrospray ionization mass spectrometry (HPLC-DAD-ESIMS). Essential oils from the flowers of these cultivars were analyzed by gas chromatography–mass spectrometry (GC-MS). The mutant cultivars, ‘ARTI-Dark Chocolate’, ‘ARTI-Purple Lady’, ‘ARTI-Purple’, and ‘ARTI-Queen’ showed higher total amounts of flavonoid and phenolic acid compared with those of the respective original cultivars. The mutant cultivars, ‘ARTI-Dark Chocolate’, ‘ARTI-Purple Lady’ and ‘ARTI-Purple’, which produce purple to pink petals, contained more than two-times higher amounts of anthocyanins compared with those of their original cultivars. Of the mutant cultivars, ‘ARTI-Yellow Star’ in which petal color was changed to yellow, showed the greatest accumulation of carotenoids. Ninety-nine volatile compounds were detected, of which hydrocarbons and terpenoids were abundant in all cultivars analyzed. This is the first report that demonstrated the phytochemical analysis of novel chrysanthemum cultivars derived from C. morifolium hydrid using HPLC-DAD-ESIMS and GC-MS. These findings suggest that the selected mutant chrysanthemum cultivars show potential as a functional source of phytochemicals associated with the abundance of health-beneficial components, as well as good source for horticulture and pigment industries.

Cellular and molecular characteristics of pollen abortion in chrysanthemum cv. Kingfisher

Microspore degeneration at the tetrad stage is associated with tapetum degeneration retardation. Some genes and proteins related to cell senescence and death are the key factors for pollen abortion. Chrysanthemum (Chrysanthemum morifolium) is a major floriculture crop in the world, but pollen contamination is an urgent problem to be solved in chrysanthemum production. C. morifolium 'Kingfisher' is a chrysanthemum cultivar that does not contain any pollen in mature anthers, thus it is a very important material for developing chrysanthemum without pollen contamination. However, the mechanism of its pollen abortion remains unclear. In this study, the cellular and molecular mechanisms of 'Kingfisher' pollen abortion were investigated using transmission electron microscopy, RNA sequencing, isobaric tags for relative and absolute quantitation, and bioinformatics. It was found that the meiosis of microspore mother cells was normal before the tetrad stage, the microspores began to degenerate at the tetrad stage, and no microspores were observed in the anthers after the tetrad stage. In addition, transcriptomic and proteomic analyses showed that some genes and proteins related to cell senescence and death were identified to be implicated in chrysanthemum pollen abortion. These results indicated that the tetrad stage was the main period of pollen abortion, and the genes and proteins related to cell senescence and death contributed to pollen abortion. These add to our understanding of chrysanthemum pollen abortion and will be helpful for development of flowers without pollen contamination in the future.

Bacillus amyloliquefaciens L-S60 Reforms the Rhizosphere Bacterial Community and Improves Growth Conditions in Cucumber Plug Seedling

Vegetable plug seedling has become the most important way to produce vegetable seedlings in China. This seedling method can significantly improve the quality and yield of vegetables compared to conventional methods. In the process of plug seedling, chemical fertilizers or pesticides are often used to improve the yield of the seedlings albeit with increasing concerns. Meanwhile, little is known about the impact of beneficial bacteria on the rhizosphere microbiota and the growth conditions of vegetables during plug seedling. In this study, we applied a culture-independent next-generation sequencing-based approach and investigated the impact of a plant beneficial bacterium, Bacillus amyloliquefaciens L-S60, on the composition and dynamics of rhizosphere microbiota and the growth conditions of cucumbers during plug seedling. Our results showed that application of L-S60 significantly altered the structure of the bacterial community associated with the cucumber seedling; presence of beneficial rhizosphere species such as Bacillus, Rhodanobacter, Paenibacillus, Pseudomonas, Nonomuraea, and Agrobacterium was higher upon L-S60 treatment than in the control group. We also measured the impact of L-S60 application on the physiological properties of the cucumber seedlings as well as the availability of main mineral elements in the seedling at different time points during the plug seedling. Results from those measurements indicated that L-S60 application promoted growth conditions of cucumber seedlings and that more available mineral elements were detected in the cucumber seedlings from the L-S60 treated group than from the control group. The findings in this study provided evidence for the beneficial effects of plant growth-promoting rhizosphere bacteria on the bacterial community composition and growth conditions of the vegetables during plug seedling.

Morphological and physiological differences between dehiscent and indehiscent anthers of Chrysanthemum morifolium

Spray cut chrysanthemums ornamental value and vase life are rapidly reduced with an increase in the pollen dispersal of the middle tubular bisexual flowers, and excessive pollen grains floating in the air are usually harmful to people. Thus, two cultivars were selected: the dehiscent 'Qx-097' and the indehiscent 'Qx-007', to investigate the morphological, structural and physiological differences in anthers. (1) Prior to the opening of the tubular flower, the anther was completely dehisced, and the pollen grains of 'Qx-097' were then released. 'Qx-007' inflorescences showed no pollen dispersal, and this cultivar was therefore not contaminated by its own pollen grains during flowering. (2) The anther cell structure of 'Qx-007' was abnormal, such that the entire anther wall exhibited hypertrophy due to the non-selective thickening of the endothecium cell size in different areas. Moreover, cracks did not form in the 'Qx-007' anther due to failure of septum degradation and stomium breakage, which resulted in the anther locules being inwardly crushed. Besides, the indehiscent anther accompanies partial pollen abortion due to the impairment of tapetum development, this is not conducive to pollen dispersal. (3) The 'Qx-007' anther contained higher water levels compared with 'Qx-097', and the dehydration of the 'Qx-007' anther was relatively moderate. Furthermore, the 'Qx-007' anther exhibited higher Ca²⁺ and Mg²⁺ levels compared with 'Qx-097' during dehiscing periods. (4) The 'Qx-007' anther showed significantly lower jasmonic acid levels and higher indole-3-acetic acid levels compare with the 'Qx-097' anther. These results suggest that the endothecium, septum and stomium constituent of the anther structure exhibit developmental abnormalities, which likely serve as the cellular basis of anther indehiscence. In addition, anther dehydration, the enhancement of anther cell toughness due to a high level of ions, and JA (IAA) dysregulation may be the determining physiological factors of anther indehiscence.

Chromosome doubling to overcome the chrysanthemum cross barrier based on insight from transcriptomic and proteomic analyses

Background

Cross breeding is the most commonly used method in chrysanthemum (Chrysanthemum morifolium) breeding; however, cross barriers always exist in these combinations. Many studies have shown that paternal chromosome doubling can often overcome hybridization barriers during cross breeding, although the underlying mechanism has seldom been investigated.

Results

In this study, we performed two crosses: C. morifolium (pollen receptor) × diploid C. nankingense (pollen donor) and C. morifolium × tetraploid C. nankingense. Seeds were obtained only from the latter cross. RNA-Seq and isobaric tags for relative and absolute quantitation (iTRAQ) were used to investigate differentially expressed genes and proteins during key embryo development stages in the latter cross. A previously performed cross, C. morifolium × diploid C. nankingense, was compared to our results and revealed that transcription factors (i.e., the agamous-like MADS-box protein AGL80 and the leucine-rich repeat receptor protein kinase EXS), hormone-responsive genes (auxin-binding protein 1), genes and proteins related to metabolism (ATP-citrate synthase, citrate synthase and malate dehydrogenase) and other genes reported to contribute to embryo development (i.e., LEA, elongation factor and tubulin) had higher expression levels in the C. morifolium × tetraploid C. nankingense cross. In contrast, genes related to senescence and cell death were down-regulated in the C. morifolium × tetraploid C. nankingense cross.

Conclusions

The data resources helped elucidate the gene and protein expression profiles and identify functional genes during different development stages. When the chromosomes from the male parent are doubled, the genes contributing to normal embryo developmentare more abundant. However, genes with negative functions were suppressed, suggesting that chromosome doubling may epigenetically inhibit the expression of these genes and allow the embryo to develop normally.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-016-2939-0) contains supplementary material, which is available to authorized users.

Anthocyanin and Carotenoid Contents in Different Cultivars of Chrysanthemum (Dendranthema grandiflorum Ramat.) Flower

The flowers of twenty-three cultivars of Dendranthema grandiflorum Ramat. were investigated to determine anthocyanin and carotenoid levels and to confirm the effects of the pigments on the flower colors using high-performance liquid chromatography (HPLC) and electrospray ionization-mass spectrometry (ESI-MS). The cultivars contained the anthocyanins cyanidin 3-glucoside (C3g) and cyanidin 3-(3ʺ-malonoyl) glucoside (C3mg) and the following carotenoids: lutein, zeaxanthin, β-cryptoxanthin, 13-cis-β-carotene, α-carotene, trans-β-carotene, and 9-cis-β-carotene. The cultivar “Magic” showed the greatest accumulation of total and individual anthocyanins, including C3g and C3gm. On the other hand, the highest level of lutein and zeaxanthin was noted in the cultivar “Il Weol”. The cultivar “Anastasia” contained the highest amount of carotenoids such as trans-β-carotene, 9-cis-β-carotene, and 13-cis-β-carotene. The highest accumulation of β-cryptoxanthin and α-carotene was noted in the cultivar “Anastasia” and “Il Weol”. Our results suggested that ‘Magic”, “Angel” and “Relance’ had high amounts of anthocyanins and showed a wide range of red and purple colors in their petals, whereas “Il Weol’, “Popcorn Ball’ and “Anastasia” produced higher carotenoid contents and displayed yellow or green petal colors. Interestingly, “Green Pang Pang”, which contained a high level of anthocyanins and a medium level of carotenoids, showed the deep green colored petals. “Kastelli”, had high level of carotenoids as well as a medium level of anthocyanins and showed orange and red colored petals. It was concluded that each pigment is responsible for the petal’s colors and the compositions of the pigments affect their flower colors and that the cultivars could be a good source for pharmaceutical, floriculture, and pigment industries.