Cloning and functional analysis of three aphid alarm pheromone genes from German chamomile (Matricaria chamomilla L.)

Functional analysis of (E)-β-farnesene synthases involved in accumulation of (E)-β-farnesene in German chamomile (Matricaria chamomilla L.)

German chamomile (Matricaria chamomilla L.) is a traditional medicinal aromatic plant, and the sesquiterpenoids in its flowers have important medicinal value. The (E)-β-farnesene (EβF) is one of the active sesquiterpenoid components and is also a major component of aphid alarm pheromones. In this study, two EβF synthase (βFS) genes (McβFS1 and McβFS2), were cloned from German chamomile. Subcellular localization analysis showed that both McβFS1 and McβFS2 were localized in the cytoplasm and nucleus. Tissue-specific expression analysis revealed that McβFS1 and McβFS2 were expressed in all flower stages, with the highest levels observed during the tubular flower extension stage. Prokaryotic expression and enzyme activity results showed that McβFS1 and McβFS2 possess catalytic activity. Overexpression of McβFS1 and McβFS2 in the hairy roots of German chamomile led to the accumulation of EβF, demonstrating enzyme activity in vivo. The promoters of McβFS1 and McβFS2 were cloned and analyzed. After treating German chamomile with methyl jasmonate (MeJA) and methyl salicylate (MeSA), the transcription levels of McβFS1 and McβFS2 were found to be regulated by both hormones. In addition, feeding experiments showed that aphid infestation upregulated the expression levels of McβFS1 and McβFS2. Our study provides valuable insights into the biosynthesis of EβF, laying a foundation for further research into its metabolic pathways.

The Role of (E)-β-Farnesene in Tritrophic Interactions: Biosynthesis, Chemoreception, and Evolution

(E)-β-farnesene (EBF) stands out as a crucial volatile organic compound, exerting significant influence on the complex interactions between plants, aphids, and predator insects. Serving as an alarm signal within aphids, EBF is also emitted by plants as a defense mechanism to attract aphid predators. This review delves into EBF sources, functions, biosynthesis, detection mechanisms, and its coevolutionary impacts on aphids and insect predators. The exploration underscores the need to comprehend the biophysical and structural foundations of EBF receptors in aphids, emphasizing their role in unraveling the intricate patterns and mechanisms of interaction between EBF and target receptors. Furthermore, we advocate for adopting structure-based or machine-learning methodologies to anticipate receptor-ligand interactions. On the basis of this knowledge, we propose future research directions aiming at designing, optimizing, and screening more stable and efficient active odorants. A pivotal outcome of this comprehensive investigation aims to contribute to the development of more effective aphid-targeted control strategies.

Nocturnal burst emissions of germacrene D from the open disk florets of pyrethrum flowers induce moths to oviposit on a nonhost and improve pollination success

Recent studies show that nocturnal pollinators may be more important to ecosystem function and food production than is currently appreciated. Here, we describe an agricultural field study of pyrethrum (Tanacetum cinerariifolium) flower pollination. Pyrethrum is genetically self-incompatible and thus is reliant on pollinators for seed set. Our pollinator exclusion experiment showed that nocturnal insects, particularly moths, significantly contribute to seed set and quality. We discovered that the most abundant floral volatile, the sesquiterpene (-)-germacrene D (GD), is key in attracting the noctuid moths Peridroma saucia and Helicoverpa armigera. Germacrene D synthase (GDS) gene expression regulates the specific GD production and accumulation in flowers, which, in contrast to related species, lose the habit of closing at night. We did observe that female moths also oviposited on pyrethrum leaves and flower peduncles, but found that only a small fraction of those eggs hatched. Larvae were severely stunted in development, most likely due to the presence of pyrethrin defense compounds. This example of exploitative mutualism, which blocks the reproductive success of the moth pollinator and depends on nocturnal interactions, is placed into an ecological context to explain why it may have developed.

Isolation and characterisation of sesquiterpene synthase from aromatic orchid Phalaenopsis bellina (Rchb.f.) Christenson

BACKGROUND

Phalaenopsis bellina, an orchid native to Borneo, is renowned for its unique appearance. It releases distinct fragrances, which have been linked to the presence of terpenoids. However, the identification and study of sesquiterpene synthase in P. bellina remain limited. In this study, we examines the functional characterisation of terpene synthase (TPS) from P. bellina, known as PbTS, through recombinant protein expression and its manifestation in the flower.

METHODS AND RESULTS

Gene annotation of PbTS revealed that the inferred peptide sequence of PbTS comprises 1,680 bp nucleotides encoding 559 amino acids with an estimated molecular mass of 65.2 kDa and a pI value of 5.4. A similarity search against GenBank showed that PbTS shares similarities with the previously published partial sequence of P. bellina (ABW98504.1) and Phalaenopsis equestris (XP_020597359.1 and ABW98503.1). Intriguingly, the phylogenetic analysis places the PbTS gene within the TPS-a group. In silico analysis of PbTS demonstrated stable interactions with farnesyl pyrophosphate (FPP), geranyl pyrophosphate (GPP), and geranylgeranyl pyrophosphate (GGPP). To verify this activity, an in vitro enzyme assay was performed on the PbTS recombinant protein, which successfully converted FPP, GPP, and GGPP into acyclic sesquiterpene β-farnesene, yielding approximately 0.03 mg/L. Expressional analysis revealed that the PbTS transcript was highly expressed in P. bellina, but its level did not correlate with β-farnesene levels across various flowering time points and stages.

CONCLUSION

The insights gained from this study will enhance the understanding of terpenoid production in P. bellina and aid in the discovery of novel fragrance-related genes in other orchid species.

Establishment and validation of a callus tissue transformation system for German chamomile (Matricaria chamomilla L.)

BACKGROUND

German chamomile (Matricaria chamomilla L.) is an important medicinal plant, and the essential oils in the flowers have various biological activities. Genetic transformation systems are important for plant quality improvement and molecular research. To the best of our knowledge, a genetic transformation system has not yet been reported for German chamomile.

RESULTS

In this study, we developed Agrobacterium-mediated transformation protocols for German chamomile callus tissues. This involved optimizing key parameters, such as hygromycin and cefotaxime concentrations, bacterial density, and infection and co-culture durations. We also performed gas chromatography-mass spectrometry analysis to identify volatile compounds in non-transgenic and transgenic callus and hairy root tissues. Furthermore, to compare and verify the callus transformation system of German chamomile, we transferred McFPS to the hairy roots of German chamomile. The results showed that the optimal conditions for Agrobacterium-mediated callus tissue transformation were as follows: explant, petiole; cefotaxime concentration, 300 mg/L; hygromycin concentration, 10 mg/L; and bacterial solution concentration, OD600 = 0.6; callus transformation efficiency was the highest when the co-culture time was 3 days.

CONCLUSIONS

Establishment of a high-efficiency callus transformation system will lay the foundation for gene function identification in German chamomile.

Biosynthesis of α-Bisabolol by Farnesyl Diphosphate Synthase and α-Bisabolol Synthase and Their Related Transcription Factors in Matricaria recutita L

The essential oil of German chamomile (Matricaria recutita L.) is widely used in food, cosmetics, and the pharmaceutical industry. α-Bisabolol is the main active substance in German chamomile. Farnesyl diphosphate synthase (FPS) and α-bisabolol synthase (BBS) are key enzymes related to the α-bisabolol biosynthesis pathway. However, little is known about the α-bisabolol biosynthesis pathway in German chamomile, especially the transcription factors (TFs) related to the regulation of α-bisabolol synthesis. In this study, we identified MrFPS and MrBBS and investigated their functions by prokaryotic expression and expression in hairy root cells of German chamomile. The results suggest that MrFPS is the key enzyme in the production of sesquiterpenoids, and MrBBS catalyzes the reaction that produces α-bisabolol. Subcellular localization analysis showed that both MrFPS and MrBBS proteins were located in the cytosol. The expression levels of both MrFPS and MrBBS were highest in the extension period of ray florets. Furthermore, we cloned and analyzed the promoters of MrFPS and MrBBS. A large number of cis-acting elements related to light responsiveness, hormone response elements, and cis-regulatory elements that serve as putative binding sites for specific TFs in response to various biotic and abiotic stresses were identified. We identified and studied TFs related to MrFPS and MrBBS, including WRKY, AP2, and MYB. Our findings reveal the biosynthesis and regulation of α-bisabolol in German chamomile and provide novel insights for the production of α-bisabolol using synthetic biology methods.

A Comprehensive Study of Therapeutic Applications of Chamomile

Chamomile has a long history of traditional medicinal uses. The two commonly used varieties with therapeutic applications are German chamomile known as Matricaria chamomilla L. and Roman chamomile or Chamaemelum nobile L. The plant contains many components, namely, flavonoids, terpenoids, and coumarins, which are responsible for its medicinal properties. The review discusses recent developments that help in establishing its role as a therapeutic agent in various areas as an anti-inflammatory, antioxidant, analgesic, antimicrobial, hepatoprotective, anti-allergic, anticancer, and anti-hypertensive agent. Not much is known about its role in the treatment of CNS disorders and metabolic syndromes, which are also discussed. The chemical components responsible for the therapeutic activity and the respective mechanism of action are also elaborated.

A Comprehensive Review on Biology, Genetic Improvement, Agro and Process Technology of German Chamomile (Matricaria chamomilla L.)

German chamomile (M. chamomilla) is recognized as a star herb due to its medicinal and aromatic properties. This plant is found across a wide range of climatic and soil conditions. Both the flower heads and blue essential oils of German chamomile possess several pharmacological properties of an anti-inflammatory, antimicrobial, antiseptic, antispasmodic and sedative, etc., nature, which makes it a highly sought after herb for use in many pharma and aroma industries. Chamomile tea, prepared from its flower heads, is also a well-known herbal tea for mind and body relaxation. Though it is a high-demand herb, farmers have not adopted this plant for large scale cultivation as a crop, which could improve their livelihood, due to the high cost in flower heads harvesting, loss in over mature and immature flower heads picking during harvesting, unavailability of varieties and agrotechnologies for machine harvesting, a lack of efficient process development of oil extraction and in the lack of improved stable varieties. There are many studies that have reported on the phytochemistry and pharmacological uses of chamomile, which further explore its importance in the medicine industry. Several studies are also present in the literature on its cultivation practices and plant ecology. However, studies on breeding behavior, genetic improvement, varietal development and mechanical harvesting are scarce in German chamomile. Hence, keeping in mind various aspects of farmers' and researchers' interest, earlier reports on taxonomy, floral biology, processing of oil extraction, active constituents, uses, agronomy, breeding challenges and opportunities in German chamomile are summarized in this review.

Taxonomic Insights and Its Type Cyclization Correlation of Volatile Sesquiterpenes in Vitex Species and Potential Source Insecticidal Compounds: A Review

Sesquiterpenes (SS) are secondary metabolites formed by the bonding of 3 isoprene (C5) units. They play an important role in the defense and signaling of plants to adapt to the environment, face stress, and communicate with the outside world, and their evolutionary history is closely related to their physiological functions. This review considers their presence and extensively summarizes the 156 sesquiterpenes identified in Vitextaxa, emphasizing those with higher concentrations and frequency among species and correlating with the insecticidal activities and defensive responses reported in the literature. In addition, we classify the SS based on their chemical structures and addresses cyclization in biosynthetic origin. Most relevant sesquiterpenes of the Vitex genus are derived from the germacredienyl cation mainly via bicyclogermacrene and germacrene C, giving rise to aromadrendanes, a skeleton with the highest number of representative compounds in this genus, and 6,9-guaiadiene, respectively, indicating the production of 1.10-cyclizing sesquiterpene synthases. These enzymes can play an important role in the chemosystematics of the genus from their corresponding routes and cyclizations, constituting a new approach to chemotaxonomy. In conclusion, this review is a compilation of detailed information on the profile of sesquiterpene in the Vitex genus and, thus, points to new unexplored horizons for future research.