Molecular structure and the second introns variation of gene F3'H of two medicinal Chrysanthemum morifolium populations

Clarifying Recent Adaptive Diversification of the Chrysanthemum-Group on the Basis of an Updated Multilocus Phylogeny of Subtribe Artemisiinae (Asteraceae: Anthemideae)

Understanding the roles played by geography and ecology in driving species diversification and in the maintenance of species cohesion is the central objective of evolutionary and ecological studies. The multi-phased orogenesis of Qinghai-Tibetan Plateau (QTP) and global climate changes over late-Miocene has profoundly influenced the environments and evolution of organisms in this region and the vast areas of Asia. In this study, we investigate the lineage diversification of Chrysanthemum-group in subtribe Artemisiinae (tribe Anthemideae, Asteraceae) likely under the effects of climate changes during this period. Using DNA sequences of seven low-copy nuclear loci and nrITS and the coalescent analytical methods, a time-calibrated phylogeny of subtribe Artemisiinae was reconstructed with emphasis on Chrysanthemum-group. The monophyletic Chrysanthemum-group was well resolved into two major clades corresponding to Chrysanthemum and Ajania, two genera which can be well identified by capitulum morphology but have been intermingled in previous plastid and ITS trees. Within Chrysanthemum, a later divergence between Ch. indicum-complex and Ch. zawadskii-complex can be recognized. The time frames of these sequential divergences coincide with the late Cenozoic uplift of the Northern QTP and the concomitant climatic heterogeneity between eastern and inland Asia. Reconstruction of historical biogeography suggested the origin of Chrysanthemum-group in Central Asia, followed by eastward migration of Chrysanthemum and in situ diversification of Ajania. Within Chrysanthemum, Ch. indicum-complex and Ch. zawadskii-complex exhibited contemporary distributional division, the former in more southern and the latter in more northern regions. The geographic structure of the three lineages in Chrysanthemum-group have been associated with the niche differentiation, and environmental heterogenization in Asia interior.

Widely Targeted Metabolomics Analysis Reveals the Effect of Flooding Stress on the Synthesis of Flavonoids in Chrysanthemum morifolium

Chrysanthemum morifolium. cv "Hangju" is an important medicinal material with many functions in China. Flavonoids as the main secondary metabolites are a major class of medicinal components in "Hangju" and its composition and content can change significantly after flooding. This study mimicked the flooding stress of "Hangju" during flower bud differentiation and detected its metabolites in different growth stages. From widely targeted metabolomics data, 661 metabolites were detected, of which 46 differential metabolites exist simultaneously in the different growth stages of "Hangju". The top three types of the 46 differential metabolites were flavone C-glycosides, flavonol and flavone. Our results demonstrated that the accumulation of flavonoids in different growth stages of "Hangju" was different; however, quercetin, eriodictyol and most of the flavone C-glycosides were significantly enhanced in the two stages after flooding stress. The expression of key enzyme genes in the flavonoid synthesis pathway were determined using RT-qPCR, which verified the consistency of the expression levels of CHI, F3H, DFR and ANS with the content of the corresponding flavonoids. A regulatory network of flavonoid biosynthesis was established to illustrate that flooding stress can change the accumulation of flavonoids by affecting the expression of the corresponding key enzymes in the flavonoid synthesis pathway.

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.

Development of SSR Markers and Assessment of Genetic Diversity in Medicinal Chrysanthemum morifolium Cultivars

Chrysanthemum morifolium, is a well-known flowering plant worldwide, and has a high commercial, floricultural, and medicinal value. In this study, simple-sequence repeat (SSR) markers were generated from EST datasets and were applied to assess the genetic diversity among 32 cultivars. A total of 218 in silico SSR loci were identified from 7300 C. morifolium ESTs retrieved from GenBank. Of all SSR loci, 61.47% of them (134) were hexa-nucleotide repeats, followed by tri-nucleotide repeats (17.89%), di-nucleotide repeats (12.39%), tetra-nucleotide repeats (4.13%), and penta-nucleotide repeats (4.13%). In this study, 17 novel EST-SSR markers were verified. Along with 38 SSR markers reported previously, 55 C. morifolium SSR markers were selected for further genetic diversity analysis. PCR amplification of these EST-SSRs produced 1319 fragments, 1306 of which showed polymorphism. The average polymorphism information content of the SSR primer pairs was 0.972 (0.938–0.993), which showed high genetic diversity among C. morifolium cultivars. Based on SSR markers, 32 C. morifolium cultivars were separated into two main groups by partitioning of the clusters using the unweighted pair group method with arithmetic mean dendrogram, which was further supported by a principal coordinate analysis plot. Phylogenetic relationship among C. morifolium cultivars as revealed by SSR markers was highly consistent with the classification of medicinal C. morifolium populations according to their origin and ecological distribution. Our results demonstrated that SSR markers were highly reproducible and informative, and could be used to evaluate genetic diversity and relationships among medicinal C. morifolium cultivars.