Leaf shape is an important quality trait of agronomic crops, and to control the law of genetic variation of leaf shape is of practical significance for improving the early identification and selection of agronomic crops. Variations in the leaf morphology of chrysanthemum cultivars are abundant, and previous studies have quantitatively defined and classified the leaf morphology of chrysanthemum; however, the genetic architecture of chrysanthemum leaves has not been elucidated to date. In this study, two pairs of F₁ hybrid populations were constructed by using small-flower chrysanthemum varieties with differences in leaf traits, and the genetic variation rules of these important quantitative traits were further discussed based on the major gene and polygene mixed inheritance analyses. The results showed that the leaves in blade shape (LBS), leaf length/width is controlled by two pairs of additive-dominant major genes (B-1), the widest part length/leaf length is controlled by two completely dominant genes (B-5); in leaf lobe shape (LLS), the lobe length/vein length is controlled by one pair of additive dominant major genes (A-1); and the lobe length/lobe width is controlled by two pairs of additive dominant major genes (B-2). The heritability of major genes was greater than 30%. For the leaf petiole shape (LPS), the petiole length is controlled by a pair of additive-dominant major genes (A-1). The results showed that the leaf traits were mainly controlled by genetic factors. In addition, based on the high-density genetic map of one F₁ hybrid population, it was found that 51 quantitative trait loci (QTL) were used to control the leaf traits, including two QTLs that controlled the LBS. There were 18 QTLs that controlled LLS. Moreover, the primary QTLs that controlled leaf width and lobe length were obtained. The results of this study may establish a theoretical foundation for the in-depth exploration of leaf-shape-related genes in chrysanthemum and may provide a reference for future research investigating leaf-shape genetics in other agronomic crops.

Leucanthemella linearis is a marsh plant in the family Compositae. It has good water and moisture resistance and ornamental properties, which makes it one of the important materials for chrysanthemum breeding and genetic improvement. The NST1 (NAC secondary wall enhancement factor 1) gene is associated with the thickening of the secondary walls of fiber cells in the plant ducts and the secondary xylem and plays an important role in plant stress resistance. In this study, two variable spliceosomes of the NST1 gene were identified from a chrysanthemum plant by using bioinformatics, qRT-PCR, transgene, and paraffin section methods to explore the molecular mechanism of the variable splicing of NST1 under abiotic stress. The results show that only three amino acids were found to be different between the two LlNST1 variants. After being treated with salt, drought, and low temperatures, analysis of the expression levels of the LlNST1 and LlNST1.1 genes in Ll showed that LlNST1.1 could respond to low temperatures and salt stress and had a weak response to drought stress. However, the expression level of LlNST1 under the three treatments was lower than that of LlNST1.1. LlNST1 transgenic tobacco showed increased saline–alkali resistance and low-temperature resistance at the seedling stage. LlNST1.1 transgenic tobacco also showed enhanced saline–alkali resistance and drought resistance at the seedling stage. In conclusion, the functions of the two variable spliceosomes of the NST1 gene are very different under abiotic stress. Therefore, this study verified the function of the variable spliceosome of NST1 and improved the stress resistance of the chrysanthemum plant under examination by regulating the expression of the NST protein, which lays a material foundation for the improvement of plant stress resistance materials and has important significance for the study of the resistance of chrysanthemum plants to abiotic stress.

The Asteraceae are widely distributed throughout the world, with diverse functions and large genomes. Many of these genes remain undiscovered and unstudied. In this study, we discovered a new gene ClNUM1 in Chrysanthemum lavandulifolium and studied its function. In this study, bioinformatics, RT-qPCR, paraffin sectioning, and tobacco transgenics were utilized to bioinformatically analyze and functionally study the three variable splice variants of the unknown gene ClNUM1 cloned from C. lavandulifolium. The results showed that ClNUM1.1 and ClNUM1.2 had selective 3′ splicing and selective 5′ splicing, and ClNUM1.3 had selective 5′ splicing. When the corresponding transgenic tobacco plants were subjected to abiotic stress treatment, in the tobacco seedlings, the ClNUM1.1 gene and the ClNUM1.2 gene enhanced salt and low-temperature tolerance and the ClNUM1.3 gene enhanced low-temperature tolerance; in mature tobacco plants, the ClNUM1.1 gene was able to enhance salt and low-temperature tolerance, and the ClNUM1.2 and ClNUM1.3 genes were able to enhance low-temperature tolerance. In summary, there are differences in the functions of the different splice variants and the different seedling stages of transgenic tobacco, but all of them enhanced the resistance of tobacco to a certain extent. The analysis and functional characterization of the ClNUM1 gene provided new potential genes and research directions for abiotic resistance breeding in Chrysanthemum.

Background: Chrysanthemum (Chrysanthemum×morifolium Ramat.) is a particularly important autumn perennial flower for potted plant, flower bed and border, and cut flower with high ornamental value. However, abiotic stress can affect the ornamental quality of Chrysanthemum. NAC (NAM, ATAF1-2, and CUC2) transcription factors (TFs) play an important role in regulating plant growth and development, as well as responding to abiotic stresses. Methods: In this study, the ClBRN1 (Chrysanthemum lavandulifolium BEARSKIN gene) was isolated from the Chrysanthemum model plant C. lavandulifolium. And analyze the function of the gene through bioinformatics, subcellular localization and overexpression. Results: Bioinformatics analysis showed that the ClBRN1 gene was a member of the NAC TFs family, with a CDS (coding sequence) length of 1,080 bp and encoding 359 amino acids. The subcellular localization results found that the gene was located in the nucleus and cell membrane. Furthermore, the transgenic results in Arabidopsis thaliana showed that the gene significantly reduces plant height while improving salt and low temperature tolerance. Observation of paraffin sections of Arabidopsis stems also revealed that the secondary cell wall of overexpressing Arabidopsis stems was significantly thicker than that of wild-type. The above results indicate that the ClBRN1 gene may play an important role in regulating plant resistance to abiotic stress. This study will provide new insights for molecular breeding of resistant chrysanthemums in the future.

Flower bud differentiation is of great significance for understanding plant evolution and ecological adaptability. The development of flower buds and mixed buds in the dichasial inflorescence of Geranium koreanum was described in this paper. The morphogenesis, surface structure, and organ morphology at different growth stages of G. koreanum buds were examined in detail using scanning electron microscope and stereo microscope. The development of mixed buds started from the flattened apical meristem. The stipule and leaf primordia arose first. Subsequently, the hemispherical meristem was divided into two hemispheres, forming a terminal bud and floral bud primordia, followed by lateral bud differentiation. The formation of the terminal and lateral buds of G. koreanum was sequential and their differentiation positions were also different. The floral bud primordia would develop into two flower units and four bracts. The primordia of a flower bud first formed the sepal primordia, then the stamen and petal primordia, and finally the pistil primordia. Compared to the stamen primordia, the growth of the petal primordia was slower. Finally, all organs, especially the petals and pistil, grew rapidly. When the pistil and petals exceeded the stamens and the petals changed color, the flower bud was ready to bloom.

Ajania purpurea is a small semi-shrub in the Asteraceae family. Its corolla is purplish red from the middle to the top, and its leaves and flowers are all fragrant. It can be introduced and cultivated as ornamental plants. In order to survive adversity, plants actively regulate the expression of stress response genes and transcripts. Alternative splicing is a common phenomenon and an important regulation mode of eukaryotic gene transcription, which plays an important role in various biological processes. In this study, four splice variants of the NST1 gene were identified from A. purpurea, and the molecular mechanism of NST1 alternative splice variants involved in abiotic stress was explored through bioinformatics, transgenics and paraffin sectionalization. The analysis of amino acid sequences showed that ApNST1.1 had alternative 5′splicing, ApNST1.2 had alternative 3′splicing and ApNST1 had the two splicing types. The main conclusions from studying transgenic tobacco seedlings and adult seedlings under abiotic stress were as follows: ApNST1, ApNST1.1 and ApNST1.3 showed salt tolerance at seedling stage, especially ApNST1.3. At the mature seedling stage, the stem height of ApNST1.1 increased significantly, and ApNST1.1 showed obvious salt tolerance, while ApNST1.2 showed obvious cold resistance. Compared to Super35S::GFP, the xylem of ApNST1 thickened by 94 μm, and the cell wall thickened by 0.215 μm. These results are of great significance to the breeding and application of ApNST1 to select splice variants with more resistance to abiotic stress, and to future study in this area. At the same time, they provide a new direction for A. purpurea breeding, and increase the possibility of garden applications.