Divergence of 10 satellite repeats in Artemisia (Asteraceae: Anthemideae) based on sequential fluorescence in situ hybridization analysis: evidence for species identification and evolution.

Artemisia is a large genus encompassing about 400 diverse species, many of which have considerable medicinal and ecological value. However, complex morphological information and variation in ploidy level and nuclear DNA content have presented challenges for evolution studies of this genus. Consequently, taxonomic inconsistencies within the genus persist, hindering the utilization of such large plant resources. Researchers have utilized satellite DNAs to aid in chromosome identification, species classification, and evolutionary studies due to their significant sequence and copy number variation between species and close relatives. In the present study, the RepeatExplorer2 pipeline was utilized to identify 10 satellite DNAs from three species (Artemisia annua, Artemisia vulgaris, Artemisia viridisquama), and fluorescence in situ hybridization confirmed their distribution on chromosomes in 24 species, including 19 Artemisia species with 5 outgroup species from Ajania and Chrysanthemum. Signals of satellite DNAs exhibited substantial differences between species. We obtained one genus-specific satellite from the sequences. Additionally, molecular cytogenetic maps were constructed for Artemisia vulgaris, Artemisia leucophylla, and Artemisia viridisquama. One species (Artemisia verbenacea) showed a FISH distribution pattern suggestive of an allotriploid origin. Heteromorphic FISH signals between homologous chromosomes in Artemisia plants were observed at a high level. Additionally, the relative relationships between species were discussed by comparing ideograms. The results of the present study provide new insights into the accurate identification and taxonomy of the Artemisia genus using molecular cytological methods.

Five Post-Translational Modification Residues of CmPT2 Play Key Roles in Yeast and Rice.

Chrysanthemum (Chrysanthemum morifolium Ramat.) is one of the largest cut flowers in the world. Phosphate transporter Pht1 family member CmPht1;2 protein (CmPT2) plays an important role in response to low-phosphate (LP) stress in chrysanthemum. Post-translational modification (PTM) can modulate the function of proteins in multiple ways. Here, we used yeast and rice systems to study the role of putative PTM in CmPT2 by determining the effect of mutation of key amino acid residues of putative glycosylation, phosphorylation, and myristoylation sites. We chose nine amino acid residues in the putative PTM sites and mutated them to alanine (A) (Cmphts). CmPT2 recovered the growth of yeast strain MB192 under LP conditions. However, G84A, G222A, T239A, Y242A, and N422A mutants could not grow normally under LP conditions. Analysis of phosphorus absorption kinetics showed that the Km of CmPT2 was 65.7 µM. Among the nine Cmphts, the expression of five with larger Km (124.4-397.5 µM) than CmPT2 was further evaluated in rice. Overexpression of CmPT2-OE increased plant height, effective panicle numbers, branch numbers, and yield compared with that of wild type 'Wuyunjing No. 7' (W7). Overexpression of Cmphts-OE led to decreased plant height and effective panicle numbers compared with that of the CmPT2-OE strain. The Pi content in roots of CmPT2-OE was higher than that of the W7 under both high (normal) phosphate (HP) and LP conditions. However, the Pi content in the leaves and roots was significantly lower in the N422A-OE strain than in the CmPT2-OE strain under both HP and LP conditions. Under LP conditions, the phosphorus starvation response (PSR) genes in CmPT2-OE were inhibited at the transcription level. The expression patterns of phosphorus-related genes in T239A, Y242A, and N422A-OE under LP conditions were different from those of CmPT2-OE. In conclusion, these five post-translational modification residues of CmPT2 play key roles in modulating the function of CmPT2. This work boosters our understanding of the function of phosphate transporters and provides genetic resources for improving the efficiency of phosphorus utilization in crop plants.

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.

Concentration-dependent emission of floral scent terpenoids from diverse cultivars of Chrysanthemum morifolium and their wild relatives.

Floral scent is an important trait that has a significant influence on the reproduction of many flowering plants and the market value of several ornamental crops. The family of Asteraceae is well known for its unique floral structure (capitulum) that consists of many florets. Although the constituents of either floral essential oils or emitted floral volatiles have been reported in many species of Asteraceae, little information is available on the mechanisms that determine floral volatile emission. In the present study, a total of 44 species/varieties of Chrysanthemum were analyzed to determine the relationship between the internal accumulation of floral terpenoids and their release as volatiles. By performing both headspace collection and organic extraction, it has been found that the emission rates of floral terpenoids are largely correlated to their internal concentrations. Particularly, the flowers of cultivated C. morifolium, when compared to their wild relatives, were found to exhibit lower emission rates that contain lowered concentrations of floral terpenoids. The differences were largely determined by six monoterpenes and five sesquiterpenes that were revealed by principal component analysis. Besides, the relationship between concentrations and emission rates of floral terpenoids as well as the sizes of capitulum was studied in detail. Separated into three different parts, disc florets were found to have a larger contribution to floral volatile emission than ray florets, whereas the phyllaries and receptacles are the main parts of volatiles accumulation. Finally, the potential biosynthetic pathway of the floral terpenoids produced in capitula of Chrysanthemum was proposed. In summary, our findings on the diversity and variations of floral terpenoids in Chrysanthemum reveal correlations between their production and emission. These findings can be useful to develop different plant breeding methods to create novel aromatic cultivars of Chrysanthemum.

Diverse Terpenoids and Their Associated Antifungal Properties from Roots of Different Cultivars of Chrysanthemum Morifolium Ramat.

Roots provide anchorage and enable the absorption of water and micronutrients from the soil for plants. Besides these essential functions, roots are increasingly being recognized as an important organ for the production of diverse secondary metabolites. The goal of this study was to investigate the chemical composition and function of terpenoid secondary metabolites in roots of different cultivars of the popular ornamental plant Chrysanthemum morifolium Ramat. Although C. morifolium is known for rich production of secondary metabolites in its flower heads and leaves, the diversity of secondary metabolites in roots remains poorly characterized. In this study, 12 cultivars of C. morifolium were selected for comparative analysis. From their roots, a total of 20 terpenoids were detected, including four monoterpenes, 15 sesquiterpenes, and one diterpene. The cultivar 'She Yang Hong Xin Ju' exhibited the highest concentration of total terpenoids at approximately 730 µg·g-1 fresh weight. Most cultivars contained sesquiterpenes as the predominant terpenoids. Of them, (E)-ß-farnesene was detected in all cultivars. Based on their terpenoid composition, the 12 cultivars were planed into four groups. To gain insights into the function of root secondary metabolites, we performed bioassays to assess their effects on growth of three species of pathogenic fungi: Fusarium oxysporum, Magnaporthe oryzae, and Verticillium dahliae. Significant variability in antifungal activity of the root extracts among different cultivars were observed. The cultivar 'Xiao Huang Ju' was the only cultivar that had significant inhibitory effects on all three species of fungi. Our study reveals the diversity of terpenoids in roots of C. morifolium and their function as a chemical defense against fungi.

Transcriptomic and proteomic analysis reveals mechanisms of low pollen-pistil compatibility during water lily cross breeding.

BACKGROUND: In water lily (Nymphaea) hybrid breeding, breeders often encounter non-viable seeds, which make it difficult to transfer desired or targeted genes of different Nymphaea germplasm. We found that pre-fertilization barriers were the main factor in the failure of the hybridization of Nymphaea. The mechanism of low compatibility between the pollen and stigma remains unclear; therefore, we studied the differences of stigma transcripts and proteomes at 0, 2, and 6 h after pollination (HAP). Moreover, some regulatory genes and functional proteins that may cause low pollen-pistil compatibility in Nymphaea were identified. RESULTS: RNA-seq was performed for three comparisons (2 vs 0 HAP, 6 vs 2 HAP, 6 vs 0 HAP), and the number of differentially expressed genes (DEGs) was 8789 (4680 were up-regulated), 6401 (3020 were up-regulated), and 11,284 (6148 were up-regulated), respectively. Using label-free analysis, 75 (2 vs 0 HAP) proteins (43 increased and 32 decreased), nine (6 vs 2 HAP) proteins (three increased and six decreased), and 90 (6 vs 0 HAP) proteins (52 increased and 38 decreased) were defined as differentially expressed proteins (DEPs). Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses revealed that the DEGs and DEPs were mainly involved in cell wall organization or biogenesis, S-adenosylmethionine (SAM) metabolism, hydrogen peroxide decomposition and metabolism, reactive oxygen species (ROS) metabolism, secondary metabolism, secondary metabolite biosynthesis, and phenylpropanoid biosynthesis. CONCLUSIONS: Our transcriptomic and proteomic analysis highlighted specific genes, incuding those in ROS metabolism, biosynthesis of flavonoids, SAM metabolism, cell wall organization or biogenesis and phenylpropanoid biosynthesis that warrant further study in investigations of the pollen-stigma interaction of water lily. This study strengthens our understanding of the mechanism of low pollen-pistil compatibility in Nymphaea at the molecular level, and provides a theoretical basis for overcoming the pre-fertilization barriers in Nymphaea in the future.

Characterization of Composition and Antifungal Properties of Leaf Secondary Metabolites from Thirteen Cultivars of Chrysanthemum morifolium Ramat.

Chrysanthemum morifolium Ramat is an ornamental plant of worldwide cultivation. Like many other species in the family Asteraceae, C. morifolium is a rich producer of secondary metabolites. There are two objectives in this study: (I) to determine and compare the diversity of apolar secondary metabolites among different cultivars of C. morifolium and (II) to compare their properties as antifungal agents. To attain these objectives, we selected 13 cultivars of C. morifolium that are commonly used for making chrysanthemum tea as experimental materials. Leaves at the same developmental stage were collected from respective mature plants and subjected to organic extraction. The extracts were analyzed using gas chromatography-mass spectrometry. A total of 37 apolar secondary metabolites including 26 terpenoids were detected from the 13 cultivars. These 13 cultivars can be largely divided into three chemotypes based on chemical principal components analysis. Next, the extracts from the 13 cultivars were examined in in vitro assays for their antifungal properties against three species of pathogenic fungi: Fusarium oxysporum, Magnaporthe oryzae, and Verticillium dahliae. Significant variability in antifungal activity of the leaf extracts among different cultivars was observed. The 13 cultivars can be divided into four groups based on their antifungal activities, which could be partly correlated to the contents of terpenoids. In short, this study reveals large variations in chemical composition, particularly of terpenoids, of leaf secondary metabolites among different cultivars of C. morifolium and their different abilities in functioning as antifungal agents.

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.

The Chrysanthemum nankingense Genome Provides Insights into the Evolution and Diversification of Chrysanthemum Flowers and Medicinal Traits.

The Asteraceae (Compositae), a large plant family of approximately 24 000-35 000 species, accounts for ∼10% of all angiosperm species and contributes a lot to plant diversity. The most representative members of the Asteraceae are the economically important chrysanthemums (Chrysanthemum L.) that diversified through reticulate evolution. Biodiversity is typically created by multiple evolutionary mechanisms such as whole-genome duplication (WGD) or polyploidization and locally repetitive genome expansion. However, the lack of genomic data from chrysanthemum species has prevented an in-depth analysis of the evolutionary mechanisms involved in their diversification. Here, we used Oxford Nanopore long-read technology to sequence the diploid Chrysanthemum nankingense genome, which represents one of the progenitor genomes of domesticated chrysanthemums. Our analysis revealed that the evolution of the C. nankingense genome was driven by bursts of repetitive element expansion and WGD events including a recent WGD that distinguishes chrysanthemum from sunflower, which diverged from chrysanthemum approximately 38.8 million years ago. Variations of ornamental and medicinal traits in chrysanthemums are linked to the expansion of candidate gene families by duplication events including paralogous gene duplication. Collectively, our study of the assembled reference genome offers new knowledge and resources to dissect the history and pattern of evolution and diversification of chrysanthemum plants, and also to accelerate their breeding and improvement.

Transcriptome analysis of differentially expressed unigenes involved in flavonoid biosynthesis during flower development of Chrysanthemum morifolium 'Chuju'.

Chrysanthemum morifolium is an ornamentally and medicinally important plant species. Up to date, molecular and genetic investigations have largely focused on determination of flowering time in the ornamental species. However, little is known about gene regulatory networks for the biosynthesis of flavonoids in the medicinal species. In the current study, we employed the high-throughput sequencing technology to profile the genome-wide transcriptome of C. morifolium 'Chuju', a famous medicinal species in traditional Chinese medicine. A total of 63,854 unigenes with an average length of 741 bp were obtained. Bioinformatic analysis has identified a great number of structural and regulatory unigenes potentially participating in the flavonoid biosynthetic pathway. According to the comparison of digital gene expression, 8,370 (3,026 up-regulated and 5,344 down-regulated), 1,348 (717 up-regulated and 631 down-regulated) and 944 (206 up-regulated and 738 down-regulated) differentially expressed unigenes (DEUs) were detected in the early, middle and mature growth phases, respectively. Among them, many DEUs were implicated in controlling the biosynthesis and composition of flavonoids from the budding to full blooming stages during flower development. Furthermore, the expression patterns of 12 unigenes involved in flavonoid biosynthesis were generally validated by using quantitative real time PCR. These findings could shed light on the molecular basis of flavonoid biosynthesis in C. morifolium 'Chuju' and provide a genetic resource for breeding varieties with improved nutritional quality.

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

KEY MESSAGE: 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.

Investigation of Differences in Fertility among Progenies from Self-Pollinated Chrysanthemum.

Most chrysanthemum cultivars are self-incompatible, so it is very difficult to create pure lines that are important in chrysanthemum breeding and theoretical studies. In our previous study, we obtained a self-compatible chrysanthemum cultivar and its self-pollinated seed set was 56.50%. It was interesting that the seed set of its ten progenies ranged from 0% to 37.23%. Examination of the factors causing the differences in the seed set will lead to an improved understanding of chrysanthemum self-incompatibility, and provide valuable information for creating pure lines. Pollen morphology, pollen germination percentage, pistil receptivity and embryo development were investigated using the in vitro culture method, the paraffin section technique, scanning electron microscopy and transmission electron microscopy. Moreover, RNA sequencing and bioinformatics were applied to analyzing the transcriptomic profiles of mature stigmas and anthers. It was found that the self-pollinated seed set of "Q10-33-1①","Q10-33-1③","Q10-33-1④" and "Q10-33-1⑩" were 37.23%, 26.77%, 7.97% and 0%, respectively. The differences in fertility among four progenies were mainly attributable to differences in pollen germination percentage and pistil receptivity. Failure of the seed set in "Q10-33-1⑩" was possibly due to self-incompatibility. In the transcriptomic files, 22 potential stigma S genes and 8 potential pollen S genes were found out.

GC-MS Analysis of the Volatile Constituents in the Leaves of 14 Compositae Plants.

The green organs, especially the leaves, of many Compositae plants possess characteristic aromas. To exploit the utility value of these germplasm resources, the constituents, mainly volatile compounds, in the leaves of 14 scented plant materials were qualitatively and quantitatively compared via gas chromatography-mass spectrometry (GC-MS). A total of 213 constituents were detected and tentatively identified in the leaf extracts, and terpenoids (especially monoterpene and sesquiterpene derivatives), accounting for 40.45-90.38% of the total compounds, were the main components. The quantitative results revealed diverse concentrations and compositions of the chemical constituents between species. Principal component analysis (PCA) showed that different groups of these Compositae plants were characterized by main components of α-thujone, germacrene D, eucalyptol, ß-caryophyllene, and camphor, for example. On the other hand, cluster memberships corresponding to the molecular phylogenetic framework, were found by hierarchical cluster analysis (HCA) based on the terpenoid composition of the tested species. These results provide a phytochemical foundation for the use of these scented Compositae plants, and for the further study of the chemotaxonomy and differential metabolism of Compositae species.

Variation in tissue Na(+) content and the activity of SOS1 genes among two species and two related genera of Chrysanthemum.

BACKGROUND: Chrysanthemum, a leading ornamental species, does not tolerate salinity stress, although some of its related species do. The current level of understanding regarding the mechanisms underlying salinity tolerance in this botanical group is still limited. RESULTS: A comparison of the physiological responses to salinity stress was made between Chrysanthemum morifolium 'Jinba' and its more tolerant relatives Crossostephium chinense, Artemisia japonica and Chrysanthemum crassum. The stress induced a higher accumulation of Na(+) and more reduction of K(+) in C. morifolium than in C. chinense, C. crassum and A. japonica, which also showed higher K(+)/Na(+) ratio. Homologs of an Na(+)/H(+) antiporter (SOS1) were isolated from each species. The gene carried by the tolerant plants were more strongly induced by salt stress than those carried by the non-tolerant ones. When expressed heterologously, they also conferred a greater degree of tolerance to a yeast mutant lacking Na(+)-pumping ATPase and plasma membrane Na(+)/H(+) antiporter activity. The data suggested that the products of AjSOS1, CrcSOS1 and CcSOS1 functioned more effectively as Na (+) excluders than those of CmSOS1. Over expression of four SOS1s improves the salinity tolerance of transgenic plants and the overexpressing plants of SOS1s from salt tolerant plants were more tolerant than that from salt sensitive plants. In addition, the importance of certain AjSOS1 residues for effective ion transport activity and salinity tolerance was established by site-directed mutagenesis and heterologous expression in yeast. CONCLUSIONS: AjSOS1, CrcSOS1 and CcSOS1 have potential as transgenes for enhancing salinity tolerance. Some of the mutations identified here may offer opportunities to better understand the mechanistic basis of salinity tolerance in the chrysanthemum complex.

Identification of floral scent in chrysanthemum cultivars and wild relatives by gas chromatography-mass spectrometry.

The objective of this study was to identify the major volatile compounds and their relative concentrations in flowers of different chrysanthemum cultivars and their wild relatives. The volatile organic components of fresh flowers were analyzed using a headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry. In total, 193 volatile organic components were detected; the major scent components were monoterpenoids and oxygenated monoterpenoids, which accounted for 68.59%-99.93% of the total volatiles in all tested materials except for Chrysanthemum indicum collected from Huangshan, in which they accounted for only 37.45% of total volatiles. The major volatile compounds were camphor, α-pinene, chrysanthenone, safranal, myrcene, eucalyptol, 2,4,5,6,7,7ab-hexahydro-1H-indene, verbenone, ß-phellandrene and camphene. In a hierarchical cluster analysis, 39 accessions of Chrysanthemum and its relatives formed six clusters based on their floral volatile compounds. In a principal component analysis, only spider type flowers were located closely on the score plot. The results of this study provide a basis for breeding chrysanthemum cultivars which desirable floral scents.

Isolation and characterization of six AP2/ERF transcription factor genes in Chrysanthemum nankingense.

The AP2/ERF family of plant transcription factors (TFs) regulate a variety of developmental and physiological processes. Here, we report the isolation of six AP2/ERF TF family genes from Chrysanthemum nankingense. On the basis of sequence similarity, one of these belonged to the Ethylene Responsive Factor (ERF) subfamily and the other five to the Dehydration Responsive Element Binding protein (DREB) subfamily. A transient expression experiment showed that all six AP2/ERF proteins localized to the nucleus. A yeast-one hybrid assay demonstrated that CnDREB1-1, 1-2 and 1-3 all function as transactivators, while CnERF1, CnDREB3-1 and 3-2 have no transcriptional activation ability. The transcription response of the six TFs in response to wounding, salinity and low temperature stress and treatment with abscisic acid (ABA), salicylic acid (SA) and jasmonic acid (JA) showed that CnERF1 was up-regulated by wounding and low temperature stress but suppressed by salinity stress. The transcription of CnDREB1-1, 1-2 and 1-3 was down-regulated by ABA and JA to varying degrees. CnDREB3-1 and 3-2 was moderately increased or decreased by wounding and SA treatment, suppressed by salinity stress and JA treatment, and enhanced by low temperature stress and ABA treatment.

Identification of chrysanthemum (Chrysanthemum morifolium) self-incompatibility.

There has been a heated argument over self-incompatibilityof chrysanthemum (Chrysanthemum morifolium) among chrysanthemum breeders. In order to solve the argument, we investigated pistil receptivity, seed set, and compatible index of 24 chrysanthemum cultivars. It was found that the 24 cultivars averagely had 3.7-36.3 pollen grains germinating on stigmas at 24 hours after self-pollination through the fluorescence microscope using aniline blue staining method. However, only 10 of them produced self-pollinated seeds, and their seed sets and compatible indexes were 0.03-56.50% and 0.04-87.50, respectively. The cultivar "Q10-33-1" had the highest seed set (56.50%) and compatible index (87.50), but ten of its progeny had a wide range of separation in seed set (0-37.23%) and compatible index (0-68.65). The results indicated that most of chrysanthemum cultivars were self-incompatible, while a small proportion of cultivars were self-compatible. In addition, there is a comprehensive separation of self-incompatibility among progeny from the same self-pollinated self-compatible chrysanthemum cultivar. Therefore, it is better to emasculate inflorescences during chrysanthemum hybridization breeding when no information concerning its self-incompatibility characteristics is available. However, if it is self-incompatible and propagated by vegetative methods, it is unnecessary to carry out emasculation when it is used as a female plant during hybridization breeding.

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

BACKGROUND: Spray cut chrysanthemum is a vital flower with high ornamental value and popularity in the world. However, the excessive quantity of pollen dispersal of most spray cut chrysanthemum is an adverse factor during its flowering stage, and can significantly reduce its ornamental value and quickly shorten its vase life. More seriously, excessive pollen grains in the air are usually harmful to people, especially for those with pollen allergies. Therefore, in order to obtain some valuable information for developing spray cut chrysanthemum with less-dispersed or non-dispersed pollen in the future breeding programs, we here investigated the factors affecting quantity of pollen dispersal of spray cut chrysanthemum with four cultivars, i.e. 'Qx-097', 'Noa', 'Qx-115', and 'Kingfisher', that have different quantity of pollen dispersal. RESULTS: 'Qx-097' with high quantity of pollen dispersal has 819 pollen grains per anther, 196.4 disk florets per inflorescence and over 800,000 pollen grains per inflorescence. The corresponding data for 'Noa' with low quantity of pollen dispersal are 406, 175.4 and over 350,000, respectively; and 219, 144.2 and nearly 160,000 for 'Qx-115' without pollen dispersal, respectively. 'Kingfisher' without pollen dispersal has 202.8 disk florets per inflorescence, but its anther has no pollen grains. In addition, 'Qx-097' has a very high degree of anther cracking that nearly causes a complete dispersal of pollen grains from its anthers. 'Noa' has a moderate degree of anther cracking, and pollen grains in its anthers are not completely dispersed. However, the anthers of 'Qx-115' and 'Kingfisher' do not crack at all. Furthermore, microsporogenesis and pollen development are normal in 'Qx-097', whereas many microspores or pollen degenerate in 'Noa', most of them abort in 'Qx-115', and all of them degrade in 'Kingfisher'. CONCLUSIONS: These results suggest that quantity of pollen dispersal in spray cut chrysanthemum are mainly determined by pollen quantity per anther, and capacity of pollen dispersal. Abnormality during microsporogenesis and pollen development significantly affects pollen quantity per anther. Capacity of pollen dispersal is closely related to the degree of anther dehiscence. The entire degeneration of microspore or pollen, or the complete failure of anther dehiscence can cause the complete failure of pollen dispersal.

Morphological, physiological, and structural responses of two species of artemisia to NaCl stress.

Effects of salt stress on Artemisia scoparia and A. vulgaris "Variegate" were examined. A. scoparia leaves became withered under NaCl treatment, whereas A. vulgaris "Variegate" leaves were not remarkably affected. Chlorophyll content decreased in both species, with a higher reduction in A. scoparia. Contents of proline, MDA, soluble carbohydrate, and Na(+) increased in both species under salt stress, but A. vulgaris "Variegate" had higher level of proline and soluble carbohydrate and lower level of MDA and Na(+). The ratios of K(+)/Na(+), Ca(2+)/Na(+), and Mg(2+)/Na(+) in A. vulgaris "Variegate" under NaCl stress were higher. Moreover, A. vulgaris "Variegate" had higher transport selectivity of K(+)/Na(+) from root to stem, stem to middle mature leaves, and upper newly developed leaves than A. scoparia under NaCl stress. A. vulgaris "Variegate" chloroplast maintained its morphological integrity under NaCl stress, whereas A. scoparia chloroplast lost integrity. The results indicated that A. scoparia is more sensitive to salt stress than A. vulgaris "Variegate." Salt tolerance is mainly related to the ability of regulating osmotic pressure through the accumulation of soluble carbohydrates and proline, and the gradient distribution of K(+) between roots and leaves was also contributed to osmotic pressure adjustment and improvement of plant salt tolerance.

Expression profile analysis of genes involved in horizontal gravitropism bending growth in the creeping shoots of ground-cover chrysanthemum by suppression subtractive hybridization.

The molecular mechanisms underlying gravitropic bending of shoots are poorly understood and how genes related with this growing progress is still unclear. To identify genes related to asymmetric growth in the creeping shoots of chrysanthemum, suppression subtractive hybridization was used to visualize differential gene expression in the upper and lower halves of creeping shoots of ground-cover chrysanthemum under gravistimulation. Sequencing of 43 selected clones produced 41 unigenes (40 singletons and 1 unigenes), which were classifiable into 9 functional categories. A notable frequency of genes involve in cell wall biosynthesis up-regulated during gravistimulation in the upper side or lower side were found, such as beta tubulin (TUB), subtilisin-like protease (SBT), Glutathione S-transferase (GST), and expensing-like protein (EXP), lipid transfer proteins (LTPs), glycine-rich protein (GRP) and membrane proteins. Our findings also highlighted the function of some metal transporter during asymmetric growth, including the boron transporter (BT) and ZIP transporter (ZT), which were thought primarily for maintaining the integrity of cell walls and played important roles in cellulose biosynthesis. CmTUB (beta tubulin) was cloned, and the expression profile and phylogeny was examined, because the cytoskeleton of plant cells involved in the plant gravitropic bending growth is well known.