Identification, Functional Characterization, and Seasonal Expression Patterns of Five Sesquiterpene Synthases in Liquidambar formosana

β-Caryophyllene wrapped by nanoliposomes efficiently increases the control effect on Bemisia tabaci MED

Bemisia tabaci poses a severe threat to plants, and the control of B. tabaci mainly relies on pesticides, which causes more and more rapidly increasing resistance. β-Caryophyllene is a promising ingredient for agricultural pest control, but its feature of poor water solubility need to be improved in practical applications. Nanotechnology can enhance the effectiveness and dispersion of volatile organic compounds (VOCs). In this study, a nanoliposome carrier was constructed by ethanol injection and ultrasonic dispersion method, and β-caryophyllene was wrapped inside it, thus solving the defect of poor solubility of β-caryophyllene. The size of the β-caryophyllene nanoliposomes (C-BT-NPs) was around 200 nm, with the absolute value of the zeta potential exceeding 30 mV and a PDI below 0.5. The stability was also maintained over a 14-d storage period. C-BT-NPs showed effective insecticidal activity against B. tabaci, with an LC50 of 1.51 g/L, outperforming thiamethoxam and offering efficient agricultural pest control. Furthermore, C-BT-NPs had minimal short-term impact on the growth of tomato plants, indicating that they are safety on plants. Therefore, the VOCs using nanoliposome preparation technology show promise in reducing reliance on conventional pesticides and present new approaches to managing agricultural pests.

Terpenoid VOC profiles and functional characterization of terpene synthases in diploid and tetraploid cytotypes of Chrysanthemum indicum L

Chrysanthemum indicum L. is a valuable medicinal plant with diploid and tetraploid forms that are widely distributed in central and southern China, and it contains abundant volatile organic compounds (VOCs). Despite the discovery of some terpene synthase (TPS) in C. indicum (i.e., CiTPS) in previous studies, many TPSs and their corresponding terpene biosynthesis pathways have yet to be discovered. In the present study, terpenoid VOCs in different tissues from two cytotypes of C. indicum were analyzed. We identified 52 types of terpenoid VOCs and systematically investigated the content and distribution of these compounds in various tissues. The two cytotypes of C. indicum exhibited different volatile terpenoid profiles. The content of monoterpenes and sesquiterpenes in the two cytotypes showed an opposite trend. In addition, four full-length candidate TPSs (named CiTPS5-8) were cloned from Ci-GD_4x, and their homologous TPS genes were screened based on the genome data of Ci-HB_2x. These eight TPSs displayed various tissue expression patterns and were discovered to produce 22 terpenoids, 5 of which are monoterpenes and 17 are sesquiterpenes. We further proposed corresponding terpene synthesis pathways, which can enable the establishment of an understanding of the volatile terpenoid profiles of C. indicum with different cytotypes. This knowledge may provide a further understanding of germplasm in C. indicum and may be useful for biotechnology applications of Chrysanthemum plants.

Rh-catalyzed regio-switchable cross-coupling of gem-difluorinated cyclopropanes with allylboronates to structurally diverse fluorinated dienes

The control of linear/branched selectivity is one of the major focuses in transition-metal catalyzed allyl-allyl cross-coupling reactions, in which bond connection occurs at the terminal site of both the allyl fragments forming different types of 1,5-dienes. Herein, terminal/internal regioselectivity is investigated and found to be switchable in allyl-allyl cross-coupling reactions between gem-difluorinated cyclopropanes and allylboronates. The controlled terminal/internal regioselectivity arises from the fine-tuning of the rhodium catalytic system. Fluorinated 1,3-dienes, 1,4-dienes and 1,5-dienes are therefore produced in good yields with respectively isomerized terminal, internal, and terminal regioselectivity.

Hedycaryol - Central Intermediates in Sesquiterpene Biosynthesis, Part II

The known sesquiterpenes that arise biosynthetically from hedycaryol are summarised. Reasonings for the assignments of their absolute configurations are discussed. The analysis provided here suggests that reprotonations at the C1=C10 double bond of hedycaryol are directed toward C1 and generally lead to 6-6 bicyclic compounds, while reprotonations at the C4=C5 double bond occur at C4 and result in 5-7 bicyclic compounds. Read more in the Review by H. Xu and J. S. Dickschat (DOI: 10.1002/chem.202200405).

Isotopic Labeling Experiments Solve the Hedycaryol Problem

Hedycaryol is a widespread sesquiterpene alcohol and important biosynthetic intermediate toward eudesmols and guaiols. A full NMR assignment for this compound has been hampered because of the unique molecular mechanics of its conformers in complex mixtures. This problem was solved through the enzymatic synthesis of isotopically labeled materials using a mutated plant and a bacterial enzyme for access to both enantiomers of hedycaryol, which also allowed us to follow the stereochemical course of its Cope rearrangement.

Functional characterization of a defense-responsive bulnesol/elemol synthase from potato

Terpene synthases (TPSs) produce a variety of terpenoids that play numerous functional roles in primary and secondary metabolism, as well as in ecological interactions. Here, we report the functional characterization of an inducible potato TPS gene encoding bulnesol/elemol synthase (StBUS/ELS). The expression of StBUS/ELS in potato leaves was significantly induced in response to both bacterial (Pseudomonas syringae) and fungal (Alternaria solani) infection as well as methyl jasmonate treatment, indicating its role in defense. The leaves exhibited the highest StBUS/ELS expression followed by the stem with least and similar expression in tuber, sprout and root. Recombinant StBUS/ELS catalyzed the formation of different sesquiterpenes by utilizing farnesyl diphosphate as substrate, and the monoterpene geraniol from geranyl diphosphate. Among the sesquiterpenes formed by StBUS/ELS, elemol was the predominant product followed by α-bulnesene, bulnesol and β-elemene. Further gas chromatography-mass spectrometry (GC-MS) analysis of StBUS/ELS assay products at different injection temperatures revealed elemol and bulnesol as the major products at 275 and 200/150°C, respectively, without much change in the levels of minor products. This indicated thermal rearrangement of bulnesol into elemol at higher temperatures. Transient overexpression of StBUS/ELS in potato leaves conferred tolerance against the growth of bacteria P. syringae and Ralstonia solanacearum, and the fungus A. solani. Further, expression analysis of pathogenesis-related (PR) genes in StBUS/ELS overexpressing leaves showed no significant change in comparison to control, indicating a direct involvement of StBUS/ELS enzymatic products against pathogens. Overall, our study suggested that StBUS/ELS is a pathogen-inducible TPS encoding bulnesol/elemol synthase and could provide a direct role in defense against biotic stress in potato.

Protective Effects of (E)-β-Caryophyllene (BCP) in Chronic Inflammation

(E)-β-caryophyllene (BCP) is a bicyclic sesquiterpene widely distributed in the plant kingdom, where it contributes a unique aroma to essential oils and has a pivotal role in the survival and evolution of higher plants. Recent studies provided evidence for protective roles of BCP in animal cells, highlighting its possible use as a novel therapeutic tool. Experimental results show the ability of BCP to reduce pro-inflammatory mediators such as tumor necrosis factor-alfa (TNF-α), interleukin-1β (IL-1β), interleukin-6 (IL-6), nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), thus ameliorating chronic pathologies characterized by inflammation and oxidative stress, in particular metabolic and neurological diseases. Through the binding to CB2 cannabinoid receptors and the interaction with members of the family of peroxisome proliferator-activated receptors (PPARs), BCP shows beneficial effects on obesity, non-alcoholic fatty liver disease/nonalcoholic steatohepatitis (NAFLD/NASH) liver diseases, diabetes, cardiovascular diseases, pain and other nervous system disorders. This review describes the current knowledge on the biosynthesis and natural sources of BCP, and reviews its role and mechanisms of action in different inflammation-related metabolic and neurologic disorders.

Nickel-catalyzed allyl–allyl coupling reactions between 1,3-dienes and allylboronates

A nickel-hydride catalysis has been developed to facilitate the allyl–allyl cross-coupling reactions between 1,3-dienes and allyl-B(pin) in excellent regioselectivity.