Osmanthus fragrans is an evergreen shrub or tree of the Oleaceae family with a long history of cultivation in Asian countries and is one of the ten traditionally famous flowers in China, with important cultural and economic value. The unique floral color and fragrance of O. fragrans are formed by a variety of endogenous metabolites that distinguish it from other flowers and exhibit extraordinary ornamental value. However, many studies on the flower color and fragrance of this plant have been mainly based on bioactive extracts and physiological characteristics, leading to a notable lack of molecular machinery and systematic research. In this review, recent advances in bioactive ingredients associated with the underlying regulatory mechanisms, as well as the prospect for industrial utilization, are comprehensively presented and critically evaluated. In particular, the isolated components and essential genes required for flower color and fragrance are also well summarized, which will provide a scientific basis for molecular breeding for ornamental applications and facilitate the discovery of novel natural products for the future industrial development of O. fragrans. In prospect, we plan to use genetic research and high-throughput omics to analyze the genes related to the flower color and fragrance of O. fragrans, and at the same time, we will hybridize and breed excellent O. fragrans varieties that are resistant to low temperature.

Alkaloids are a class of nitrogen-containing alkaline organic compounds found in nature, with significant biological activity, and are also important active ingredients in Chinese herbal medicine. Amaryllidaceae plants are rich in alkaloids, among which galanthamine, lycorine, and lycoramine are representative. Since the difficulty and high cost of synthesizing alkaloids have been the major obstacles in industrial production, particularly the molecular mechanism underlying alkaloid biosynthesis is largely unknown. Here, we determined the alkaloid content in Lycoris longituba, Lycoris incarnata, and Lycoris sprengeri, and performed a SWATH-MS (sequential window acquisition of all theoretical mass spectra)-based quantitative approach to detect proteome changes in the three Lycoris. A total of 2193 proteins were quantified, of which 720 proteins showed a difference in abundance between Ll and Ls, and 463 proteins showed a difference in abundance between Li and Ls. KEGG enrichment analysis revealed that differentially expressed proteins are distributed in specific biological processes including amino acid metabolism, starch, and sucrose metabolism, implicating a supportive role for Amaryllidaceae alkaloids metabolism in Lycoris. Furthermore, several key genes collectively known as OMT and NMT were identified, which are probably responsible for galanthamine biosynthesis. Interestingly, RNA processing-related proteins were also abundantly detected in alkaloid-rich Ll, suggesting that posttranscriptional regulation such as alternative splicing may contribute to the biosynthesis of Amaryllidaceae alkaloids. Taken together, our SWATH-MS-based proteomic investigation may reveal the differences in alkaloid contents at the protein levels, providing a comprehensive proteome reference for the regulatory metabolism of Amaryllidaceae alkaloids.

Carotenoids are important natural pigments that are responsible for the fruit and flower colors of many plants. The composition and content of carotenoid can greatly influence the color phenotype of plants. However, the regulatory mechanism underling the divergent behaviors of carotenoid accumulation, especially in flower, remains unclear. In this study, a new cultivar Osmanthus fragrans ‘Yanzhi Hong’ was used to study the regulation of carotenoid pigmentation in flower. Liquid chromatograph–mass spectrometer (LC-MS) analysis showed that β-carotene, phytoene, lycopene, γ-carotene, and lutein were the top five pigments enriched in the petals of ‘Yanzhi Hong’. Through transcriptome analysis, we found that the expression of the structural genes in carotenoid pathway was imbalanced: most of the structural genes responsible for lycopene biosynthesis were highly expressed throughout the flower developmental stages, while those for lycopene metabolism kept at a relatively lower level. The downregulation of LYCE, especially at the late developmental stages, suppressed the conversion from lycopene to α-carotene but promoted the accumulation of β-carotene, which had great effect on the carotenoid composition of ‘Yanzhi Hong’. Ethylene response factor (ERF), WRKY, basic helix-loop-helix (bHLH), v-myb avian myeloblastosis viral oncogene homolog (MYB), N-Acetylcysteine (NAC), auxin response factor (ARF), and other transcription factors (TFs) have participated in the flower color regulation of ‘Yanzhi Hong’, which formed co-expression networks with the structural genes and functioned in multiple links of the carotenoid pathway. The results suggested that the cyclization of lycopene is a key link in determining flower color. The modification of the related TFs will break the expression balance between the upstream and downstream genes and greatly influence the carotenoid profile in flowers, which can be further used for creating colorful plant germplasms.

Alternative splicing refers to the process of producing different splicing isoforms from the same pre-mRNA through different alternative splicing events, which almost participates in all stages of plant growth and development. In order to understand its role in the fruit development of Osmanthus fragrans, transcriptome sequencing and alternative splicing analysis was carried out on three stages of O. fragrans fruit (O. fragrans “Zi Yingui”). The results showed that the proportion of skipping exon events was the highest in all three periods, followed by a retained intron, and the proportion of mutually exclusive exon events was the lowest and most of the alternative splicing events occurred in the first two periods. The results of enrichment analysis of differentially expressed genes and differentially expressed isoforms showed that alpha-Linolenic acid metabolism, flavonoid biosynthesis, carotenoid biosynthesis, photosynthesis, and photosynthetic-antenna protein pathways were significantly enriched, which may play an important role in the fruit development of O. fragrans. The results of this study lay the foundation for further study of the development and maturation of O. fragrans fruit and further ideas for controlling fruit color and improving fruit quality and appearance.

Pine wilt disease (PWD) is caused by the pine wood nematode (PWN, Bursaphelenchus xylophilus) and significantly impacts pine forest ecosystems globally. This study focuses on Pinus massoniana, an important timber and oleoresin resource in China, which is highly susceptible to PWN. However, the defense mechanism of pine trees in response to PWN remains unclear. Addressing the complexities of PWD, influenced by diverse factors such as bacteria, fungi, and environment, we established a reciprocal system between PWN and P. massoniana seedlings under aseptic conditions. Utilizing combined second- and third-generation sequencing technologies, we identified 3,718 differentially expressed genes post PWN infection. Transcript analysis highlighted the activation of defense mechanisms via stilbenes, salicylic acid and jasmonic acid pathways, terpene synthesis, and induction of pathogenesis-related proteins and resistance genes, predominantly at 72 h postinfection. Notably, terpene synthesis pathways, particularly the mevalonate pathway, were crucial in defense, suggesting their significance in P. massoniana’s response to PWN. This comprehensive transcriptome profiling offers insights into P. massoniana’s intricate defense strategies against PWN under aseptic conditions, laying a foundation for future functional analyses of key resistance genes. [ ] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY 4.0 International license .

Prunus serrulata is an important landscape tree species whose flower color has high ornamental value. However, the molecular mechanisms regulating flower color in P. serrulata remain unclear. By studying the metabolomics and transcriptomics of three different color varieties under the species lineage of P. serrulata, ‘Eigeng’ (EG, white), ‘Albo-rosea’ (AR, pink), and ‘Grandiflora’ (GF, green), the biosynthetic mechanisms of different flower colors in P. serrulata were revealed. The results showed that the different colors of the petals were related to the content of chlorophyll and anthocyanins. Among these, cyanidin-3-O-glucoside and cyanidin-3-O-(6-O-malonyl-β-D-glucoside) were highly expressed in AR. A combined transcriptomic analysis revealed that five flavonoid structural genes, including two DFR genes and three UFGT genes, were specifically expressed. In addition, three key transcription factors, PsMYB77, PsMYB17, and PsMYB105, were identified as regulators of the structural genes DFR and UFGT and participants in the forward synthesis of anthocyanin. This study provides convincing evidence elucidating the regulatory mechanisms of anthocyanin synthesis of P. serrulata and provides a theoretical basis for the breeding and development of new varieties and germplasm resource innovation for cherry blossom.