Liyuan Yang

Cuphea hookeriana (Lythraceae) is an evergreen flowering shrub native to tropical and subtropical regions, serving as an ornamental plant in landscaping and as a raw material for industry and agriculture. Here, we assembled a haplotype-resolved chromosomal genome for C. hookeriana (2n = 3x = 24) based on HiFi and Hi-C sequencing datasets. The genome was assembled into 16 chromosomes with a total size of 498,761,099 bp, comprising 248,233,948 bp and 240,972,969 bp for haplotypes A and B, respectively. BUSCO evaluation indicated an assembly completeness of 97.7% C value. Approximately 30,000 genes were annotated for each haplotype, achieving a BUSCO complete score of 97%.

Chimonanthus spp. has attracted much attention due to its great ornamental value and potential medicinal value. The flowers of Chimonanthus praecox and C. salicifolius exude a strong aroma. Terpenoids are the main components of the floral volatile organic compounds (VOCs), and the synthesis of these compounds is closely related to the terpene synthase (TPS) gene. In this study, headspace-solid phase microextraction combined with gas chromatography-mass spectrometry (HS–SPME–GC–MS) was used to identify the floral components of C. praecox and C. salicifolius. 25 and 31 floral VOCs were identified from C. praecox and C. salicifolius, respectively. Combined with the published VOCs of Chimonanthus leaf, we found that monoterpenoids take most relative content of volatile in flowers while in leaves, both monoterpenoids and sesquiterpenoids have high relative content. We identified 63 and 48 TPS genes from the genomes of C. praecox and C. salicifolius. Transcriptome analysis showed that TPS-b subfamily genes (related to monoterpene synthesis) showed high expression levels in flowers and leaves, while TPS-a subfamily genes (related to sesquiterpene synthesis) showed strong expression in leaves. The TPS genes with high expression in leaves mainly evolved through tandem duplication, suggesting that tandem duplication of TPS genes may promote the synthesis of terpenoids in leaves. This study revealed the expression pattern of TPS genes in Chimonanthus plants, and proposed that the tandem duplication of TPS gene family may play an important role in the synthesis of monoterpenes in the leaves of Chimonanthus species.

The protein phosphatase 2 C (PP2C) plays a crucial role in the growth and development of plants. However, limited information on the PP2C genes in Chimonanthus spp. is available. Therefore, the comprehensive genome-wide identification and analysis of the PP2Cs gene family is necessary in Chimonanthus spp. to provide basic information for further study. In this work, 93 members of the CsPP2C gene family and 85 members of the CpPP2C gene family were identified. Based on the phylogenetic analysis, 93 CsPP2Cs and 85 CpPP2Cs genes were classified into 13 subgroups. Based on RNA-Seq data, specific expression patterns of CsPP2Cs in different tissues were identified. CsPP2C28, CsPP2C55, and CsPP2C17 showed high expression during leaf senescence, and combined with cis-element analysis, it is speculated that they may participate in regulating plant senescence. CsPP2C47, CsPP2C27, CsPP2C42, and CsPP2C41 may play an important role in responding to abscisic acid during seed dormancy and germination. These results contribute to a deeper understanding of the functions of the CsPP2C gene family and CpPP2C gene family, and providing candidate genes for genetic engineering and breeding to enhance important traits such as stress resistance and growth development in C. salicifolius and C. praecox.

Abstract Gene duplications provide evolutionary potentials for generating novel functions. Chimonanthus praecox and C. salicifolius are closely related species from Calycantaceae, Magnoliids. In this study, we compared the WRKY gene family from C. praecox and C. salicifolius, and predicted the potential gene function through gene expression patterns to explore the evolution of orthologous and paralogous gene pairs. A total of 73 and 85 WRKY genes were identified and analyzed from the whole genome sequencing of C. praecox and C. salicifolius. Based on the phylogenetic analysis, CpWRKY and CsWRKY genes were clustered into three groups (Group I、II、III) and 5 subgroups (Group IIa、IIb、IIc、IId、IIe). In C. praecox and C. salicifolius, we identified thirty-six and fifty-four pairs of WRKY segmental duplicated genes, respectively, along with two and three pairs of tandem duplicates, indicating that segmental duplication plays a crucial role in the evolution of Chimonanthus WRKY gene family. Most WRKY duplication gene pairs originated from segmental duplications before the first whole genome duplication (WGD), highlighting this period as a significant source of genetic diversity and functionality for the WRKY family. The analysis of WRKY gene expression levels suggests that CsWRKY18 and CsWRKY68 may promote the growth of the roots in C. salicifolius. Comparisons of expression profiles between species revealed that five orthologous gene pairs presented identical expression trends, indicating functional conservation and absence of neo-functionalization or sub-functionalization. However, most orthologous gene pairs exhibit differences in expression patterns, suggesting that they have undergone functional divergence. This functional differentiation may be due to the different selective pressures faced by C. praecox and C. salicifolius during their speciation processes. This study provided detailed information on the WRKY gene family from C. praecox and C. salicifolius, and a new insight for studying gene duplication and function evolution.

Lagerstroemia indica is popular for its bright flower colors and long bloom period. However, although L. indica has a long flowering period, the flowering time of a single flower is short, lasting only 1−2 d. Petal expansion is a key process that affects the length and ornamental quality of the flowering period. However, the molecular mechanism of petal expansion in L. indica remains unclear. The molecular mechanisms underlying flower opening in L. indica were investigated through transcriptome sequencing of flower buds and blooms at four developmental stages. Analysis of differentially expressed genes (DEGs) indicated enrichment in cellular processes, metabolic regulation, and biological signaling pathways. KEGG pathway analysis revealed significant roles for carbohydrate, lipid, and amino acid metabolism in the flowering process. Additional pathway analysis identified key genes and processes related to carbohydrate utilization, hormone signaling, water transport, and cell wall expansion that contribute to petal opening regulation. A comprehensive examination of the expansin gene family proteins, known for promoting cell wall loosening and extension, identified 27 expansin genes in L. indica, which were categorized into four subfamilies with conserved structures and motifs. Of these, LiEXPA10, LiEXPA19, LiEXLA1, and LiEXLA2 showed heightened expression in the later stages of flowering (S3−S4), suggesting a central role in petal expansion. Functional validation in Arabidopsis thaliana demonstrated that LiEXLA1 and LiEXLA2 promote accelerated flowering and enhanced petal expansion in transgenic lines. These findings offer new insights into the genetic and molecular basis of flower opening in L. indica and provide a foundation for breeding strategies aimed at improving ornamental traits.

The basic helix-loop-helix (bHLH) family is one of the three major transcription factor families that play important transcriptional regulatory roles in plant growth and development. One of the most crucial elements in defining Lagerstroemia indica’s decorative qualities is flower color. However, the function of the bHLH transcription factor family in L. indica anthocyanin glycoside synthesis has not been clarified. Using the transcriptome data of flower color, 79 LibHLH genes were found in this study. Phylogenetic analysis showed that the LibHLH genes can be divided into 16 subfamilies, and most of the genes in the same subfamily have similar conserved motifs. The total anthocyanin glycoside content of L. indica ‘Zihua Guifei’ petals was determined during three developmental stages of the petals’ growth. The results showed that the total anthocyanin glycoside content grew gradually with growth and development, and that it accumulated most during the full bloom stage. By using gene expression analysis, protein interaction network analysis, and bioinformatics, it was possible to determine which member of the III f family, LibHLH29, is important for the synthesis of anthocyanin glycosides in L. indica. Its expression was confirmed by qRT-PCR, and the results were essentially compatible with the transcriptome data. It was more prominent in the light-colored bloom stage the color-transition stage of L. indica ‘Zihua Guifei’. It can be further investigated as a major candidate gene for regulating anthocyanin glycoside synthesis in L. indica, thus laying the foundation for an in-depth study of the interactions among transcription factors.

Background: Orchids (Cymbidium spp.) exhibit significant variations in floral morphology, pollinator relations, and ecological habitats. Due to their exceptional economic and ornamental value, Cymbidium spp. have been commercially cultivated for centuries. SSR markers are extensively used genetic tools for biology identification and population genetics analysis. Result: In this study, nine polymorphic EST-SSR loci were isolated from Cymbidium goeringii using RNA-Seq technology. All nine SSR loci showed transferability in seven other congeneric species, including 51 cultivars. The novel SSR markers detected inter-species gene flow among the Cymbidium species and intra-species sub-division of C. goeringii and C. ensifolium, as revealed by neighborhood-joining and Structure clustering analyses. Conclusion: In this study, we developed nine microsatellites using RNA-Seq technology. These SSR markers aided in detecting potential gene flow among Cymbidium species and identified the intra-species sub-division of C. goeringii and C. ensifolium.

Background Chimonanthus praecox and Chimonanthus salicifolius are closely related species that diverged approximately six million years ago. While both C. praecox and C. salicifolius could withstand brief periods of low temperatures of – 15 °C. Their flowering times are different, C. praecox blooms in early spring, whereas C. salicifolius blooms in autumn. The SBP-box (SQUAMOSA promoter-binding protein) is a plant-specific gene family that plays a crucial vital role in regulating plant flowering. Although extensively studied in various plants, the SBP gene family remains uncharacterized in Calycanthaceae. Methods and results We conducted genome-wide identification of SBP genes in both C. praecox and C. salicifolius and comprehensively characterized the chromosomal localization, gene structure, conserved motifs, and domains of the identified SBP genes. In total, 15 and 18 SBP genes were identified in C. praecox and C. salicifolius, respectively. According to phylogenetic analysis, the SBP genes from Arabidopsis, C. praecox, and C. salicifolius were clustered into eight groups. Analysis of the gene structure and conserved protein motifs showed that SBP proteins of the same subfamily have similar motif structures. The expression patterns of SBP genes were analyzed using transcriptome data. The results revealed that more than half of the genes exhibited lower expression levels in leaves than in flowers, suggesting their potential involvement in the flower development process and may be linked to the winter and autumn flowering of C. praecox and C. salicifolius. Conclusion Thirty-three SBPs were identified in C. praecox and C. salicifolius. The evolutionary characteristics and expression patterns were examined in this study. These results provide valuable information to elucidate the evolutionary relationships of the SBP family and help determine the functional characteristics of the SBP genes in subsequent studies.

Background MIKC type MADS-box transcription factors are one of the largest gene families and play a pivotal role in flowering time and flower development. Chimonanthus salicifolius belongs to the family Calycanthaceae and has a unique flowering time and flowering morphology compared to other Chimonanthus species, but the research on MIKC type MADS-box gene family of C. salicifolius has not been reported. Objective Identification, comprehensive bioinformatic analysis, the expression pattern of MIKC-type MADS-box gene family from different tissues of C. salicifolius. Methods Genome-wide investigation and expression pattern under different tissues of the MIKC-type MADS-box gene family in C. salicifolius, and their phylogenetic relationships, evolutionary characteristics, gene structure, motif distribution, promoter cis-acting element were performed. Results A total of 29 MIKC-type MADS-box genes were identified from the whole genome sequencing. Interspecies synteny analysis revealed more significant collinearity between C. salicifolius and the magnoliids species compared to eudicots and monocots. MIKC-type MADS-box genes from the same subfamily share similar distribution patterns, gene structure, and expression patterns. Compared with Arabidopsis thaliana, Nymphaea colorata, and Chimonanthus praecox, the FLC genes were absent in C. salicifolius, while the AGL6 subfamily was expanded in C. salicifolius. The selectively expanded promoter (AGL6) and lack of repressor (FLC) genes may explain the earlier flowering in C. salicifolius. The loss of the AP3 homologous gene in C. salicifolius is probably the primary cause of the morphological distinction between C. salicifolius and C. praecox. The csAGL6a gene is specifically expressed in the flowering process and indicates the potential function of promoting flowering. Conclusion This study offers a genome-wide identification and expression profiling of the MIKC-types MADS-box genes in the C. salicifolius, and establishes the foundation for screening flowering development genes and understanding the potential function of the MIKC-types MADS-box genes in the C. salicifolius.