Glanduläre Trichome und Isoprenoidbiosynthese

The Lamiaceae family, the sixth largest among angiosperms, is renowned for its rich diversity of terpenoids, many of which exhibit remarkable bioactivities, including anti-inflammatory, psychoactive, anti-cancer, and antiviral effects. Notable examples with fully elucidated biosynthetic pathways include menthol from peppermint, forskolin from blue spur flower, and carnosol from rosemary. For other key Lamiaceae terpenes—such as the anti-cancer oridonin, the psychoactive salvinorin A, and bioactive marrubiin and vitexilactone—significant progress has been made. This review explores the bioactivity and biosynthesis of Lamiaceae terpenes, with a focus on mono- and diterpenes, while highlighting future research directions.

Fruit pigmentation is a major signal that attracts frugivores to enable seed dispersal. In most fleshy fruit, green chlorophyll typically accumulates early in development and is replaced by a range of pigments during ripening. In species such as grape and strawberry, chlorophyll is replaced by red anthocyanins produced by the flavonoid biosynthetic pathway. Eggplant (Solanum melongena) is unique, as its fruit accumulates anthocyanins beginning from fruit set, and these are later replaced by the yellow flavonoid-pathway intermediate naringenin chalcone. To decipher the genetic regulation of this extraordinary pigmentation shift, we integrated mRNA and microRNA (miRNA) profiling data obtained from developing eggplant fruit. We discovered that SQUAMOSA PROMOTER BINDING-LIKE (i.e., SPL6a, SPL10, and SPL15), MYB1, and MYB2 transcription factors (TFs) regulate anthocyanin biosynthesis in early fruit development, whereas the MYB12 TF controls later accumulation of naringenin chalcone. We further show that miRNA157 and miRNA858 negatively regulate the expression of SPLs and MYB12, respectively. Taken together, our findings suggest that opposing and complementary expression of miRNAs and TFs controls the pigmentation switch in eggplant fruit skin. Intriguingly, despite the distinctive pigmentation pattern in eggplant, fruit development in other species makes use of homologous regulatory factors to control the temporal and spatial production of different pigment classes.

Plants are naturally subjected to various types of biotic stresses, including pathogenic microorganisms and herbivory by insects, which trigger different signaling pathways and related defense mechanisms. Inoculation with microorganisms, such as plant growth-promoting rhizobacteria (PGPR), can be seen as a form of stress because it triggers a systemic resistance response in plants similar to that caused by insect herbivory. However, these interactions have typically been studied independently, which has limited the understanding of their combined effects. This study examines the effects of Bacillus amyloliquefaciens GB03 inoculation and Spodoptera frugiperda herbivory on the total phenolic contents of Ocimum basilicum. We also analyze the levels of endogenous phytohormones and the activity of phenylalanine ammonia-lyase (PAL), a crucial enzyme involved in the biosynthesis of phenolic defense-related metabolites. The results indicate that the total phenolic content significantly increased only in plants that were both inoculated by GB03 and damaged by larvae. Additionally, PAL activity showed an increase in plants that were damaged by larvae and in those subjected to the combined treatment of larval damage and inoculation with GB03. Regarding phytohormones, in plants damaged by insects, the levels of salicylic acid (SA) increased, regardless of whether they were inoculated or not, while the levels of jasmonic acid–isoleucine (JA-ile) rose in all treatments compared to the control. This study highlights the intricate relationships among beneficial microbes, herbivores, and plant defense mechanisms, emphasizing their potential impact on improving plant resilience and the production of secondary metabolites. Furthermore, understanding the independent effects of PGPR inoculation, beyond its interaction with herbivory, could provide valuable insights into its role as a sustainable alternative for enhancing plant defense responses and promoting crop productivity.

0

Terpenes, the largest class of plant specialized products, are built from C5 building blocks via terpene synthases and oxidized by cytochrome P450 enzymes (CYPs) for structural diversity. In some cases, CYPs do not simply oxidize the terpene backbone, but induce backbone rearrangements, methyl group shifts, and carbon–carbon (C–C) scissions. Some of these reactions were characterized over 25 years ago, but most of them were reported in recent years, indicating a highly dynamic research area. These reactions are involved in mono-, sesqui-, di- and triterpene metabolism and provide key catalytic steps in the biosynthesis of plant hormones, volatiles, and defense compounds. Many commercially relevant terpenoids require such reaction steps in their biosynthesis such as triptonide (rodent pest management), secoiridoids (flavor determinants), as well as ginkgolides, cardenolides, and sesquiterpene lactones with pharmaceutical potential. Here, we provide a comprehensive overview of the underlying mechanisms.

The extraction of plant essential oils (EOs) and analysis by gas chromatography coupled to mass spectrometry (GC-MS) are standard methods when studying aromatic plants and the chemical composition of EOs. Here, two simple methods for the extraction of EO compounds from leaves of Thymus vulgaris are described. Organic solvent extraction and solid-phase microextraction (SPME), respectively, are used and the results of the GC-MS analyses are compared.We explain how analyte peaks can be identified and discuss possible rearrangement reactions that can occur during the extraction process or analysis.

In plants and mammals, non-homologous end-joining is the dominant pathway to repair DNA double strand breaks, making it challenging to generate knock-in events. We identified two groups of exonucleases from the Herpes Virus and the bacteriophage T7 families that conferred an up to 38-fold increase in HDR frequencies when fused to Cas9/Cas12a in a Tobacco mosaic virus-based transient assay in Nicotiana benthamiana. We achieved precise and scar-free insertion of several kilobases of DNA both in transient and stable transformation systems. In Arabidopsis thaliana, fusion of Cas9 to a Herpes Virus family exonuclease leads to 10-fold higher frequencies of knock-ins in the first generation of transformants. In addition, we demonstrate stable and heritable knock-ins of in wheat in 1% of the primary transformants. Our results open perspectives for the routine production of heritable knock-in and gene replacement events in plants.

A bottleneck in the development of new anti‐cancer drugs is the recognition of their mode of action (MoA). Metabolomics combined with machine learning allowed to predict MoAs of novel anti‐proliferative drug candidates, focusing on human prostate cancer cells (PC‐3). As proof of concept, 38 drugs are studied with known effects on 16 key processes of cancer metabolism, profiling low molecular weight intermediates of the central carbon and cellular energy metabolism (CCEM) by LC‐MS/MS. These metabolic patterns unveiled distinct MoAs, enabling accurate MoA predictions for novel agents by machine learning. The transferability of MoA predictions based on PC‐3 cell treatments is validated with two other cancer cell models, i.e., breast cancer and Ewing\'s sarcoma, and show that correct MoA predictions for alternative cancer cells are possible, but still at some expense of prediction quality. Furthermore, metabolic profiles of treated cells yield insights into intracellular processes, exemplified for drugs inducing different types of mitochondrial dysfunction. Specifically, it is predicted that pentacyclic triterpenes inhibit oxidative phosphorylation and affect phospholipid biosynthesis, as confirmed by respiration parameters, lipidomics, and molecular docking. Using biochemical insights from individual drug treatments, this approach offers new opportunities, including the optimization of combinatorial drug applications.

Plant immunity is a multilayered process that includes recognition of patterns or effectors from pathogens to elicit defense responses. These include the induction of a cocktail of defense metabolites that typically restrict pathogen virulence. Here, we investigate the interaction between barley roots and the fungal pathogens Bipolaris sorokiniana (Bs) and Fusarium graminearum (Fg) at the metabolite level. We identify hordedanes, a previously undescribed set of labdane-related diterpenoids with antimicrobial properties, as critical players in these interactions. Infection of barley roots by Bs and Fg elicits hordedane synthesis from a 600-kb gene cluster. Heterologous reconstruction of the biosynthesis pathway in yeast and Nicotiana benthamiana produced several hordedanes, including one of the most functionally decorated products 19-b-hydroxy-hordetrienoic acid (19-OH-HTA). Barley mutants in the diterpene synthase genes of this cluster are unable to produce hordedanes but, unexpectedly, show reduced Bs colonization. By contrast, colonization by Fusarium graminearum, another fungal pathogen of barley and wheat, is 4-fold higher in the mutants completely lacking hordedanes. Accordingly, 19-OH-HTA enhances both germination and growth of Bs, whereas it inhibits other pathogenic fungi, including Fg. Analysis of microscopy and transcriptomics data suggest that hordedanes delay the necrotrophic phase of Bs. Taken together, these results show that adapted pathogens such as Bs can subvert plant metabolic defenses to facilitate root colonization.

Methylerythritol cyclodiphosphate (MEcPP) is an intermediate in the biosynthesis of isoprenoids in plant plastids and in bacteria, and acts as a stress signal in plants. Here, we show that MEcPP regulates biofilm formation in Escherichia coli K-12 MG1655. Increased MEcPP levels, triggered by genetic manipulation or oxidative stress, inhibit biofilm development and production of fimbriae. Deletion of fimE, encoding a protein known to downregulate production of adhesive fimbriae, restores biofilm formation in cells with elevated MEcPP levels. Limited proteolysis-coupled mass spectrometry (LiP-MS) reveals that MEcPP interacts with the global regulatory protein H-NS, which is known to repress transcription of fimE. MEcPP prevents the binding of H-NS to the fimE promoter. Therefore, our results indicate that MEcPP can regulate biofilm formation by modulating H-NS activity and thus reducing fimbriae production. Further research is needed to test whether MEcPP plays similar regulatory roles in other bacteria.