Haiyan Li

Bougainvillea (Bougainvillea glabra) is a perennial woody species belonging to the Nyctaginaceae family, native to South America. It is widely recognized for its brightly colored bracts and strong adaptability, and is widely cultivated as a major ornamental plant in tropical and subtropical regions. However, QTL mapping studies on morphological traits remain limited in the genus Bougainvillea, and the genetic basis underlying its key ornamental traits is still largely unclear. In this study, an F₁ segregating population was constructed using the cultivars ‘Mrs Eva White’ and ‘Formosa’ as parents, and was used for high-density genetic map construction and quantitative trait locus analysis. Fourteen leaf and thorn-related traits were investigated, with coefficients of variation ranging from 8.16% to 64.54%. Based on specific-locus amplified fragment sequencing (SLAF-seq), a total of 1,133,206 SLAF markers were developed, among which 479,488 were polymorphic. Using the inclusive composite interval mapping (ICIM) algorithm in the GACD 1.2 software, a high-density genetic linkage map was constructed for B. glabra, consisting of 17 linkage groups and 3256 markers. The genetic map spanned 1797.64 cM, with an average marker interval of 0.55 cM. A total of 22 QTLs were detected for the measured leaf and thorn traits, including 16 major QTLs with a PVE ≥ 8%. Collectively, this study identified stable genetic loci for important morphological traits and provides a valuable theoretical foundation for marker-assisted selection and genetic improvement of ornamental traits in Bougainvillea.

Anthurium andraeanum Linden is a prominent ornamental plant belonging to the family Araceae and is cultivated worldwide. The morphology characteristics are crucial because they significantly impact ornamental values, commercial properties, and the efficiency of space utilization in production. However, only a few related investigations have been conducted in anthurium to date. In this study, an F₁ genetic segregation population containing 160 progenies was generated through hybridization between potted and cut anthurium varieties. Fifteen morphological traits were assessed and revealed substantial levels of genetic variation and widespread positive correlation. Based on specific length amplified fragment (SLAF) sequencing technology, 8171 single nucleotide polymorphism (SNP) markers were developed, and the high-density linkage map of 2202.27 cM in length distributed on 15 linkage groups was constructed successfully, with an average distance of 0.30 cM. Using the inclusive composite interval mapping (ICIM) method, 59 QTLs related to 15 key morphological traits were successfully identified, which explained phenotypic variance (PVE) ranging from 6.21% to 17.74%. Thirty-three of those associated with 13 traits were designated as major QTLs with PVE > 10%. These findings offer valuable insights into the genetic basis of quantitative traits and are beneficial for molecular marker-assisted selection (MAS) in anthurium breeding.

Osmanthus fragrans is widely grown for the purpose of urban greening and the pleasant aroma emitted from its flowers. The floral scent is determined by several monoterpenoid volatiles, such as linalool and its oxides, which are a few of the most common volatiles and the main components of the essential oils in most sweet osmanthus cultivars. In addition, the relative contents of cis- and trans-linalool oxide (furan) may affect the aromas and quality of the essential oils. MYB proteins represent the largest family of transcription factors in plants and participate in regulating secondary metabolites. Several cis-elements, especially AC-rich regions, are known to be bound by 2R-MYBs and could be found in the promoter of the enzyme genes in the terpenoid metabolic pathway. However, there has to date been no investigation into the 2R-MYB family genes involved in regulating terpenoid biosynthesis in O. fragrans. Here, 243 non-redundant 2R-MYB proteins were grouped into 33 clusters based on the phylogeny and exon-intron distribution. These genes were unevenly distributed on 23 chromosomes. Ka/Ks analysis showed that the major mode of 2R-MYB gene evolution was purifying selection. Expression analysis indicated that 2R-MYB genes in O. fragrans exhibited varied expression patterns. A total of 35 OfMYBs representing the highest per kilobase per million mapped reads in the flower were selected for quantitative real-time PCR analysis. The correlation analysis between the expression level and the contents of fragrant compounds at different flowering stages suggested that OfMYB19/20 exhibited remarkably positive correlation with the accumulation of cis-linalool oxides. OfMYB51/65/88/121/137/144 showed significantly negative correlations with one or more linalool oxides. Characterization of these proteins revealed that OfMYB19 and OfMYB137 were localized in the nuclei, but did not show transcriptional activation in the yeast system, which suggested that they may be bound to other transcription factors to exert regulatory functions. These findings provide useful information for further functional investigation of the 2R-MYBs and offer a foundation for clarifying the 2R-MYB transcription factors involved in the molecular mechanism of the regulation of monoterpenoid biosynthesis in Osmanthus fragrans.

Auxins have long been implicated in many aspects of plant growth and development. Auxin response factors (ARFs) are important proteins in auxin-mediated pathways and they play key roles in plant physiological and biochemical processes, including flower development. Endogenous indoleacetic acid (IAA) levels were measured and ARFs were studied in the flowers during the developmental stages in order to further elucidate the role of auxin in flower development of Osmanthus fragrans. A systematic analysis of OfARFs was conducted by carrying out a genome-wide search of ARFs. A total of 50 ARF genes (OfARFs) were detected and validated from the Osmanthus fragrans genome. Furthermore, a comprehensive overview of the OfARFs was undertaken, including phylogenetic relationship, gene structures, conserved domains, motifs, promoters, chromosome locations, gene duplications, and subcellular locations of the gene product. Finally, expression profiling, while using transcriptome sequencing from a previous study and quantitative real-time PCR (qRT-PCR), revealed that many OfARF genes have different expression levels in various tissues and flower developmental stages. By comparing the expression profiles among the flower developmental stages, and the relationship between ARFs and endogenous IAA levels, it can be supposed that OfARFs function in flower development of O. fragrans in an auxin-mediated pathway.

Osmanthus fragrans, or “RiXiangGui”, is an ornamental, woody, evergreen plant that is cultivated widely because it blooms recurrently and emits a strong fragrance. Recently, the germplasm resources, classification, and aroma compositions of O. fragrans have been investigated. However, the molecular mechanisms of the floral scent formation and regulation have remained largely unknown. To obtain a global perspective on the molecular mechanism of the aroma formation during blooming, nine RNA Sequencing (RNA-Seq) libraries were constructed from three flowering stages: The initial, full, and final flowering stage. In short, a total of 523,961,310 high-quality clean reads were assembled into 136,611unigenes, with an average sequence length of 792 bp. About 47.43% of the unigenes (64,795) could be annotated in the NCBI non-redundant protein database. A number of candidate genes were identified in the terpenoid metabolic pathways and 1327 transcription factors (TFs), which showed differential expression patterns among the floral scent formation stages, were also identified, especially OfMYB1, OfMYB6, OfWRKY1, and OfWRKY3, which could play critical roles in the floral scent formation. These results indicated that the floral scent formation of O. fragrans was a very complex process which involved a large number of TFs. This study provides reliable resources for further studies of the O.fragrans floral scent formation.