Genome-wide identification and characterization analysis of RWP-RK family genes reveal their role in flowering time of Chrysanthemum lavandulifolium.

BACKGROUND: RWP-RKs are plant specific transcription factors, which are widely distributed in plants in the form of polygenic families and play key role in nitrogen absorption and utilization, and are crucial to plant growth and development. However, the genome-wide identification and function of RWP-RK in Compositae plants are widely unknown. RESULTS: In this study, 101 RWP-RKs in Chrysanthemum lavandulifolium were identified and tandem repeat was an important way for the expansion of RWP-RKs in Compositae species. 101 RWP-RKs contain 38 NIN-like proteins (NLPs) and 31 RWP- RK domain proteins (RKDs), as well as 32 specific expansion members. qRT-PCR results showed that 7 ClNLPs in leaves were up-regulated at the floral transition stage, 10 ClNLPs were negatively regulated by low nitrate conditions, and 3 of them were up-regulated by optimal nitrate conditions. In addition, the flowering time of Chrysanthemum lavandulifolium was advanced under optimal nitrate conditions, the expression level of Cryptochromes (ClCRYs), phytochrome C (ClPHYC) and the floral integration genes GIGANTEA (ClGI), CONSTANS-LIKE (ClCOL1, ClCOL4, ClCOL5), FLOWERING LOCUS T (ClFT), FLOWERING LOCUS C (ClFLC), SUPPRESSOR OF OVER-EXPRESSION OF CONSTANS 1 (ClSOC1) also were up-regulated. The expression level of ClCRY1a, ClCRY1c, ClCRY2a and ClCRY2c in the vegetative growth stage induced by optimal nitrate reached the expression level induced by short-day in the reproductive growth stage, which supplemented the induction effect of short-day on the transcription level of floral-related genes in advance. CONCLUSIONS: It was speculated that ClNLPs may act on the photoperiodic pathway under optimal nitrate environment, and ultimately regulate the flowering time by up-regulating the transcription level of ClCRYs. These results provide new perspective for exploring the mechanism of nitrate/nitrogen affecting flowering in higher plants.

cla-miR164-NO APICAL MERISTEM (ClNAM) regulates the inflorescence architecture development of Chrysanthemum lavandulifolium.

Chrysanthemum × morifolium has great ornamental and economic value on account of its exquisite capitulum. However, previous studies have mainly focused on the corolla morphology of the capitulum. Such an approach cannot explain the variable inflorescence architecture of the chrysanthemum. Previous research from our group has shown that NO APICAL MERISTEM (ClNAM) is likely to function as a hub gene in capitulum architecture in the early development stage. In the present study, ClNAM was used to investigate the function of these boundary genes in the capitulum architecture of Chrysanthemum lavandulifolium, a closely related species of C. × morifolium in the genus. Modification of ClNAM in C. lavandulifolium resulted in an advanced initiation of the floral primordium at the capitulum. As a result, the receptacle morphology was altered and the number of florets decreased. The ray floret corolla was shortened, but the disc floret was elongated. The number of capitula increased significantly, arranged in more densely compounded corymbose synflorescences. The yeast and luciferase reporter system revealed that ClAP1, ClRCD2, and ClLBD18 target and activate ClNAM. Subsequently, ClNAM targets and activates ClCUC2a/c, which regulates the initiation of floral and inflorescence in C. lavandulifolium. ClNAM was also targeted and cleaved by cla-miR164 in this process. In conclusion, this study established a boundary gene regulatory network with cla-miR164-ClNAM as the hub. This network not only influences the architecture of capitulum, but also affects compound corymbose synflorescences of the C. lavandulifolium. These results provide new insights into the mechanisms regulating inflorescence architecture in chrysanthemum.

Development and Validation of a Novel Nomogram to Predict Hypoalbuminemia among Patients with Stroke in the Neurocritical Care Unit.

This study aimed to investigate hypoalbuminemia-related factors in patients with stroke in the neurocritical care unit (NCU) and to establish a nomogram model for hypoalbuminemia prediction. Data from 902 patients hospitalized for stroke in the NCU who had normal albumin levels on admission from March 2018 to December 2020 were analyzed. Logistic regression was used to identify the risk factors associated with hypoalbuminemia. A novel nomogram prediction model for hypoalbuminemia was constructed, and it was validated in an independent set (n = 233). The nomogram incorporated seven risk factors, including age, high comorbidity, mechanical ventilation, feeding routes, total protein, high-sensitivity C-reactive protein, and fibrinogen levels, and its area under the curve for predicting hypoalbuminemia in the developmental set and validation set were 0.856 and 0.870, respectively. The novel nomogram facilitates risk prediction of hypoalbuminemia among patients with stroke in the NCU, which might be useful for selecting treatment strategies and management.

Genome-wide identification of the MIKCc-type MADS-box gene family in Chrysanthemum lavandulifolium reveals their roles in the capitulum development.

Chrysanthemum ×morifolium is well known throughout the world for its diverse and exquisite flower types. However, due to the complicated genetic background of C. ×morifolium, it is difficult to understand the molecular mechanism of its flower development. And it limits the molecular breeding of improving chrysanthemum flower types. C. ×morifolium has the typical radial capitulum, and many researches showed that the members of the MIKCc-type MADS box gene family play a key role in the formation and development of the capitulum. However, it has been difficult to isolate the important MIKCc and investigate their roles in this process due to the lack of genomic information in chrysanthemum. Here, we identified MIKCc-type MADS box genes at whole genome-wide level in C. lavandulifolium, a diploid species closely related to C. ×morifolium, and investigated their roles in capitulum development by gene expression pattern analysis and protein interaction analysis. A total of 40 ClMIKCc were identified and were phylogenetically grouped into 12 clades. Members of all clades showed different enriched expression patterns during capitulum formation. We speculate that the E-class genes in C. lavandulifolium underwent subfunctionalization because they have a significantly expanded, more diverse expression patterns, and specifically tissue expression than AtSEPs. Meanwhile, we detected the C-class expressed in disc floret corolla, which could be the clue to explore the morphological differences between disc and ray floret corolla. In addition, the potential roles of some MIKCcs in complex inflorescence formation were explored by comparing the number and phylogenetic relationship of MIKCc subfamily members in Asteraceae with different capitulum types. Members of the FLC branch in Asteraceae were found to be possibly related to the differentiation and development of the ray floret.

Genome-wide identification of the TCP gene family in Chrysanthemum lavandulifolium and its homologs expression patterns during flower development in different Chrysanthemum species.

TCP proteins, part of the transcription factors specific to plants, are recognized for their involvement in various aspects of plant growth and development. Nevertheless, a thorough investigation of TCPs in Chrysanthemum lavandulifolium, a prominent ancestral species of cultivated chrysanthemum and an excellent model material for investigating ray floret (RF) and disc floret (DF) development in Chrysanthemum, remains unexplored yet. Herein, a comprehensive study was performed to analyze the genome-wide distribution of TCPs in C. lavandulifolium. In total, 39 TCPs in C. lavandulifolium were identified, showing uneven distribution on 8 chromosomes. Phylogenetic and gene structural analyses revealed that ClTCPs were grouped into classes I and II. The class II genes were subdivided into two subclades, the CIN and CYC/TB1 subclades, with members of each clade having similar conserved motifs and gene structures. Four CIN subclade genes (ClTCP24, ClTCP25, ClTCP26, and ClTCP27) contained the potential miR319 target sites. Promoter analysis revealed that ClTCPs had numerous cis-regulatory elements associated with phytohormone responses, stress responses, and plant growth/development. The expression patterns of ClTCPs during capitulum development and in two different florets were determined using RNA-seq and qRT-PCR. The expression levels of TCPs varied in six development stages of capitula; 25 out of the 36 TCPs genes were specifically expressed in flowers. Additionally, we identified six key ClCYC2 genes, which belong to the class II TCP subclade, with markedly upregulated expression in RFs compared with DFs, and these genes exhibited similar expression patterns in the two florets of Chrysanthemum species. It is speculated that they may be responsible for RFs and DFs development. Subcellular localization and transactivation activity analyses of six candidate genes demonstrated that all of them were localized in the nucleus, while three exhibited self-activation activities. This research provided a better understanding of TCPs in C. lavandulifolium and laid a foundation for unraveling the mechanism by which important TCPs involved in the capitulum development.

Floral Development Stage-Specific Transcriptomic Analysis Reveals the Formation Mechanism of Different Shapes of Ray Florets in Chrysanthemum.

The formation mechanism of different ray floret shapes of chrysanthemum (Chrysanthemum × morifolium) remains elusive due to its complex genetic background. C. vestitum, with the basic ray floret shapes of the flat, spoon, and tubular types, is considered a model material for studying ray floret morphogenesis. In this study, the flat and tubular type lines of C. vestitum at specific stages were used to investigate the key genes that regulate morphological differences in ray florets. We found that the expression levels of genes related to auxin synthesis, transport, and response were generally higher in the tubular type than in the flat type. CvARF3 was highly expressed in the flat type, while CvARF5 and CvARF6 were highly expressed in the tubular type. Additionally, the transcription levels of Class B and E genes closely related to petal development, including CvPI, CvAP3, Cvdefh21, CvSEP3, and CvCDM77, were expressed at higher levels in the tubular type than the flat type. Based on the results, it is proposed that auxin plays a key role in the development of ray florets, and auxin-related genes, especially CvARFs, may be key genes to control the morphological difference of ray florets. Simultaneously, MADS-box genes are involved in the co-regulation of ray floret morphogenesis. The results provide novel insights into the molecular mechanism of different petal type formation and lay a theoretical foundation for the directional breeding of petal type in chrysanthemums.

The mechanisms of optimal nitrogen conditions to accelerate flowering of Chrysanthemum vestitum under short day based on transcriptome analysis.

Nitrogen (N) plays an important role in the development of plants, with N application having been shown to accelerate flowering of cultivated plants. However, the mechanism of optimal N conditions to accelerate flowering of short-day plants is still unclear. In this study, it was found that Chrysanthemum vestitum is a typical short-day plant like most chrysanthemum varieties, and its flowering must go through a short-day induction stage. Further observations on the growth of C. vestitum showed that the N range of external application for growth was limited to between 0.25 and 2.50 mM. The results showed that, under optimal N (ON, 1.25 mM) conditions, the plants increased rapidly and flowering time was advanced; under high N (HN, 2.50 mM) or limited N (LN, 0.25 mM) conditions, the growth of plants were inhibited and flowering time was delayed. On the basis of transcriptome data, analysis of differentially expressed genes (DEGs) revealed that the floral-related genes B-box19 (BBX19), Cryptochromes (CRYs), CONSTANS-like (COLs), nitrate transporter protein (NRT), and NIN-like protein (NLP) could respond to N availability. Most of the genes in the photoperiod pathway were upregulated by ON conditions, and their expression was inhibited under HN and LN conditions. Our findings indicated that N could affect flowering by regulating the transcription levels of genes that are involved mainly in the photoperiod pathway. These candidate genes provide important clues for the subsequent analysis of the mechanism of N-induced flowering of short-day plants, and provide a possibility to improve the flowering of chrysanthemum by molecular breeding.

The chrysanthemum lavandulifolium genome and the molecular mechanism underlying diverse capitulum types.

Cultivated chrysanthemum (Chrysanthemum × morifolium Ramat.) is a beloved ornamental crop due to the diverse capitula types among varieties, but the molecular mechanism of capitulum development remains unclear. Here, we report a 2.60 Gb chromosome-scale reference genome of C. lavandulifolium, a wild Chrysanthemum species found in China, Korea and Japan. The evolutionary analysis of the genome revealed that only recent tandem duplications occurred in the C. lavandulifolium genome after the shared whole genome triplication (WGT) in Asteraceae. Based on the transcriptomic profiling of six important developmental stages of the radiate capitulum in C. lavandulifolium, we found genes in the MADS-box, TCP, NAC and LOB gene families that were involved in disc and ray floret primordia differentiation. Notably, NAM and LOB30 homologs were specifically expressed in the radiate capitulum, suggesting their pivotal roles in the genetic network of disc and ray floret primordia differentiation in chrysanthemum. The present study not only provides a high-quality reference genome of chrysanthemum but also provides insight into the molecular mechanism underlying the diverse capitulum types in chrysanthemum.

New Insights into Co-pyrolysis among Graphitic Carbon Nitride and Organic Compounds: Carbonaceous Gas Fragments Induced Synthesis of Ultrathin Mesoporous Nitrogen-Doped Carbon Nanosheets for Heterogeneous Catalysis.

N-doped carbon materials are well known as promising metal-free catalysts and applied in innumerable industrial synthetics. However, most of the N-doped carbon materials obtained by conventional synthetic means exhibit generally low mesoporosity, and their reported pore volumes reached only 1-3 cm3 g-1, which greatly limits their further industrial application in heterogeneous catalysis. Especially for oxidation reaction of alkylbenzenes, this type of reaction is almost always accompanied by many different byproducts, while the reaction activity and selectivity are mainly affected by mesoporosity of catalysts. Traditionally, graphitic carbon nitride (GCN) is commonly considered as a self-sacrificed nitrogen source together with multifarious organic compounds to obtain N-doped carbon materials by a co-pyrolysis process. However, the mechanisms of formation process are still complex and uncontrollable to date. In this work, we present a novel co-pyrolysis synthetic strategy by a facile chemical vapor deposition method for preparing a series of ultrathin N-doped carbon nanosheets with high mesoporosity. More importantly, it is found that GCN containing abundant hydrogen bonds can be irreversibly anchored by carbonaceous gas fragments (CxHy+) released from various organic substances via thermogravimetry-differential thermal analysis coupled with mass spectrometry and X-ray photoelectron spectroscopy analysis, and the CxHy+ fragments exhibit a non-negligible role during the transformation. Our results further demonstrated that the residue of incompletely decomposed GCN is a key point to enlarge porosity in final products which are obtained via mixing pyrolysis between an organic precursor and GCN (or GCN precursors). Benefitting from the outstanding mesoporosity and ultrathin morphology, the representative ABCNS-900 exhibits excellent catalytic performance for oxidizing ethylbenzene to acetophenone with extremely low dosage and high selectivity. Our findings show a universal synthetic strategy for ultrathin N-rich carbon nanosheets with a high mesopore volume, further promoting the application of N-doped carbon materials in heterogeneous catalytic industry.

In Situ Preparation and Analysis of Bimetal Co-doped Mesoporous Graphitic Carbon Nitride with Enhanced Photocatalytic Activity.

A novel photocatalyst of mesoporous graphitic carbon nitride (g-C3N4) co-doped with Co and Mo (Co/Mo-MCN) has been one-pot synthesized via a simple template-free method; cobalt chloride and molybdenum disulfide were used as the Co and Mo sources, respectively. The characterization results evidently indicate that molybdenum disulfide functions as Mo sources to incorporate Mo atoms in the framework of g-C3N4 and as a catalyst for promoting the decomposition of g-C3N4, resulting in the creation of mesopores. The obtained Co/Mo-MCN exhibited a significant enhancement of the photocatalytic activity in H2 evolution (8.6 times) and Rhodamine B degradation (10.1 times) under visible light irradiation compared to pristine g-C3N4. Furthermore, density functional theory calculations were applied to further understand the photocatalytic enhancement mechanism of the optical absorption properties at the atomic level after Co- or Mo-doping. Finite-difference time-domain simulations were performed to evaluate the effect of the mesopore structures on the light absorption capability. The results revealed that both the bimetal doping and the mesoporous architectures resulted in an enhanced optical absorption; this phenomenon was considered to have played a critical role in the improvement in the photocatalytic performance of Co/Mo-MCN.

Phylogenetic relationships in the genus Avena based on the nuclear Pgk1 gene.

The phylogenetic relationships among 76 Avena taxa, representing 14 diploids, eight tetraploids, and four hexaploids were investigated by using the nuclear plastid 3-phosphoglycerate kinase gene (Pgk1). A significant deletion (131 bp) was detected in all the C genome homoeologues which reconfirmed a major structural divergence between the A and C genomes. Phylogenetic analysis indicated the Cp genome is more closely related to the polyploid species than is the Cv genome. Two haplotypes of Pgk1 gene were obtained from most of the AB genome tetraploids. Both types of the barbata group showed a close relationship with the As genome diploid species, supporting the hypothesis that both the A and B genomes are derived from an As genome. Two haplotypes were also detected in A. agadiriana, which showed close relationships with the As genome diploid and the Ac genome diploid, respectively, emphasizing the important role of the Ac genome in the evolution of A. agadiriana. Three homoeologues of the Pgk1 gene were detected in five hexaploid accessions. The homoeologues that might represent the D genome were tightly clustered with the tetraploids A. maroccana and A. murphyi, but did not show a close relationship with any extant diploid species.