AmMYB24 Regulates Floral Terpenoid Biosynthesis Induced by Blue Light in Snapdragon Flowers

Ubiquitination of the PpMADS2 transcription factor controls linalool production during UV-B irradiation in detached peach fruit

Plant secondary metabolites undergo changes in response to UV-B irradiation. Although UV-B irradiation reduces flavor-associated volatile compounds in detached peach (Prunus persica L. Batsch) fruit, the underlying regulatory mechanisms remain unclear. By integrating proteomic, transcriptomic, and metabolomic data from peach fruit following UV-B irradiation, we discovered that the detached fruit responds to UV-B by suppressing the biosynthesis of the flavor-related monoterpene linalool. We identified PpMADS2, a transcription factor that regulates linalool biosynthesis by activating terpene synthase 1 (PpTPS1) expression. PpMADS2 overexpression in peach and tomato fruits significantly increased linalool levels compared with the controls. Proteomic data and immunoblots revealed a decrease in PpMADS2 abundance following exposure to UV-B. Moreover, our results demonstrated that PpMADS2 interacts with the E3 ubiquitin ligase PpCOP1 both in vitro and in vivo. The UV-B-induced 26S-proteasome-mediated degradation of PpMADS2 is largely PpCOP1-dependent. Taken together, our findings demonstrate that linalool biosynthesis in detached peach fruit exposed to UV-B radiation is governed by the PpCOP1-PpMADS2-PpTPS1 module. This study enhances our understanding of the interplay between light signaling and fruit flavor quality. Multiomics approaches offer valuable resources for investigating the mechanisms underlying how light influences metabolism in fruit crops.

A Comprehensive Review of Plant Volatile Terpenoids, Elucidating Interactions with Surroundings, Systematic Synthesis, Regulation, and Targeted Engineering Production

Plants require a flexible avoidance mechanism as they need to cope with external stimuli and challenges through complex specialized metabolites, among which volatile terpenoids make outstanding contributions, acting as key media signal substances in the cooperation between plants and surrounding organisms. In recent decades, the research on the identification and functional characterization of terpenoid synthase and factors regulating metabolic shunts has gained significant attention, leading to substantial progress and notable achievements. However, with the popularization of terpenoids in insect and disease prevention, medical care, cosmetics, and other fields, coupled with increasing resistance to artificially produced chemical products, the demand for natural terpenoids has outpaced supply, prompting the emergence and popularity of targeted engineering for the mass production of terpenoids using microorganisms and plants as platforms. In this paper, we provide a detailed overview of the key knowledge and research progress of volatile terpenoids with regard to multiple functions, complex synthetic pathways, key terpenoid synthase genes, related regulatory factors, and target engineering.

The Scent of Lily Flowers: Advances in the Identification, Biosynthesis, and Regulation of Fragrance Components

Lilies (Lilium spp.) are renowned for their diverse and captivating floral scents, which are highly valued both commercially and ornamentally. This review provides a comprehensive overview of recent advancements in the identification, biosynthesis, and regulation of fragrance components in lily flowers. Various volatile organic compounds (VOCs) that contribute to the unique scents of different lily species and cultivars, including terpenoids, benzenoids/phenylpropanoids, and fatty acid derivatives, are discussed. The release patterns of these compounds from different floral tissues and at different developmental stages are examined, highlighting the significant role of tepals. Detection methods such as gas chromatography-mass spectrometry (GC-MS) and sensory analysis are evaluated for their effectiveness in fragrance research. Additionally, the biosynthetic pathways of key fragrance compounds are explored, focusing on the terpenoid and benzenoid/phenylpropanoid pathways and the regulatory mechanisms involving transcription factors and environmental factors. This review also addresses the influence of genetic and environmental factors on fragrance production and proposes future research directions to enhance the aromatic qualities of lilies through selective genetic and breeding approaches. Emphasis is placed on the potential applications of these findings in the floral industry to improve the commercial value and consumer appeal of lily flowers.

LiNAC100 contributes to linalool biosynthesis by directly regulating LiLiS in Lilium 'Siberia'

MAIN CONCLUSION

The transcription factor LiNAC100 has a novel function of regulating floral fragrance by directly regulating linalool synthase gene LiLiS. Lilium 'Siberia', an Oriental hybrid, is renowned as both a cut flower and garden plant, prized for its color and fragrance. The fragrance comprises volatile organic compounds (VOCs), primarily monoterpenes found in the plant. While the primary terpene synthases in Lilium 'Siberia' were identified, the transcriptional regulation of these terpene synthase (TPS) genes remains unclear. Thus, understanding the regulatory mechanisms of monoterpene biosynthesis is crucial for breeding flower fragrance, thereby improving ornamental and commercial values. In this study, we isolated a nuclear-localized LiNAC100 transcription factor from Lilium 'Siberia'. The virus-induced gene silencing (VIGS) of LiNAC100 was found to down-regulate the expression of linalool synthase gene (LiLiS) and significantly inhibit linalool synthesis. Conversely, transient overexpression of LiNAC100 produced opposite effects. Additionally, yeast one-hybrid and dual-luciferase assays confirmed that LiNAC100 directly activates LiLiS expression. Our findings reveal that LiNAC100 plays a key role in monoterpene biosynthesis in Lilium 'Siberia', promoting linalool synthesis through the activation of LiLiS expression. These results offer insights into the molecular mechanisms of terpene biosynthesis in Lilium 'Siberia' and open avenues for biotechnological enhancement of floral scent.

Light Regulation of LoCOP1 and Its Role in Floral Scent Biosynthesis in Lilium 'Siberia'

Light is an important environmental signal that governs plant growth, development, and metabolism. Constitutive photomorphogenic 1 (COP1) is a light signaling component that plays a vital role in plant light responses. We isolated the COP1 gene (LoCOP1) from the petals of Lilium 'Siberia' and investigated its function. The LoCOP1 protein was found to be the most similar to Apostasia shenzhenica COP1. LoCOP1 was found to be an important factor located in the nucleus and played a negative regulatory role in floral scent production and emission using the virus-induced gene silencing (VIGS) approach. The yeast two-hybrid, β-galactosidase, and bimolecular fluorescence complementation (BiFC) assays revealed that LoCOP1 interacts with LoMYB1 and LoMYB3. Furthermore, light modified both the subcellular distribution of LoCOP1 and its interactions with LoMYB1 and MYB3 in onion cells. The findings highlighted an important regulatory mechanism in the light signaling system that governs scent emission in Lilium 'Siberia' by the ubiquitination and degradation of transcription factors via the proteasome pathway.

LiMYB108 is involved in floral monoterpene biosynthesis induced by light intensity in Lilium 'Siberia'

We find that the MYB family transcription factor, LiMYB108, has a novel function to regulate the floral fragrance affected by light intensity. Floral fragrance determines the commercial value of flowers and is influenced by many environmental factors, especially light intensity. However, the mechanism by which light intensity affects the release of floral fragrance is unclear. Here, we isolated an R2R3-type MYB transcription factor LiMYB108, the expression of which was induced by light intensity and located in the nucleus. Light of 200 and 600 μmol m^-1 s^-1 significantly increased the expression of LiMYB108, which was consistent with the improving trend of monoterpene synthesis under light. Virus-induced gene silencing (VIGS) of LiMYB108 in Lilium not only significantly inhibited the synthesis of ocimene and linalool, but also decreased the expression of LoTPS1; however, transient overexpression of LiMYB108 exerted opposite effects. Furthermore, yeast one-hybrid assays, dual-luciferase assays, and electrophoretic mobility shift assays (EMSA) demonstrated that LiMYB108 directly activated the expression of LoTPS1 by binding to the MYB binding site (MBS) (CAGTTG). Our findings demonstrate that light intensity triggered the high expression of LiMYB108, and then LiMYB108 as a transcription factor to activate the expression of LoTPS1, thus promoting the synthesis of the ocimene and linalool, which are important components of floral fragrance. These results provide new insights into the effects of light intensity on floral fragrance synthesis.

Transcriptome analysis identifies key gene LiMYB305 involved in monoterpene biosynthesis in Lilium 'Siberia'

Lilium is a popular cut flower that is highly favored by consumers due to its snowy white color and strong fragrance, which originates from the release of monoterpenes. However, the underlying molecular mechanism of monoterpene synthesis remains poorly understood. In this study, the content of three main monoterpenes (linalool, ocimene, and myrcene) was examined in Lilium 'Siberia', and RNA sequencing of the 11 stages of flower development was conducted. The biosynthesis of the three monoterpenes increased with flower development, reaching their peak levels at the full flowering stage. Transcriptome data revealed 257,140 unigenes, with an average size of 794 bp, from which 43,934 differentially expressed genes were identified and enriched in the KEGG pathways partly involved in plant hormone signal transduction and monoterpenoid biosynthesis. Furthermore, the essential factor LiMYB305 was identified by WGCNA after the release of the flower fragrance. The transient silencing of LiMYB305 in petals using VIGS technology showed that the mRNA expression levels of LiLiS, LiOcS, and LiMyS were significantly downregulated and that the release of linalool, ocimene, and myrcene had decreased significantly. Y1H, LUC, and EMSA experiments revealed that LiMYB305 directly bound and activated the LiOcS promoter to increase the synthesis of monoterpenes. Taken together, these results provide insight into the molecular mechanism of monoterpene synthesis and provide valuable information to investigate the formation of the flower fragrance in Lilium.