Microbial biological control agents are increasingly used as an alternative to synthetic pesticides. The application of these microorganisms massively affects all members of plant‐colonising microbial communities, including pathogenic fungi. In the majority of cases, the resulting competition for ecological niches is decided by the toxicity of microbial secondary metabolites (SMs) formed. In this study, we devised confrontation experiments employing the fungal maize pathogen Colletotrichum graminicola and antagonistic partners, that is the biocontrol bacterium Bacillus amyloliquefaciens and the ubiquitous ascomycete Aspergillus nidulans. Transcriptome studies uncovered strong de‐regulation of the vast majority of the C. graminicola secondary metabolite biosynthetic gene clusters (SMBGCs), with 69% and 86% of these clusters de‐regulated at confrontation sites with B. amyloliquefaciens or A. nidulans, respectively. In the biocontrol bacterium and in A. nidulans confronting the maize pathogen, 100% and 74% of the SMBGCs were transcriptionally de‐regulated, respectively. Correspondingly, non‐targeted high‐resolution LC–MS/MS revealed a large repertoire of 1738 and 1466 novel features formed in the fungus–bacterium and fungus–fungus confrontation, respectively. Surprisingly, several of these belong to chemical classes with lead structures of synthetic fungicides.

NMR-based Metabolomics approach assessed phytochemical profile in seed and husk of three cardamom species: Elettaria cardamomum (green), Amomum subulatum (black), and Aframomum corrorima (white). NMR Spectroscopy identified 20 metabolites belonging to sugars, amino-, organic-, fatty acids, terpenes, and phenolics. Multivariate data analyses revealed distinct metabolic profiles among the 3 species, and further in seed versus husk. A. subulatum seed showed the highest sugar and amino acid levels, while E. cardamomum seed was richer in ω-3 fatty acids. Husk, especially from A. subulatum and E. cardamomum, contained high levels of phenolic acids. Compared to other cardamom taxa, A. corrorima exhibited lower levels of most chemicals. This study highlights the potential value of cardamom husk, particularly from A. subulatum and E. cardamomum species enriched in phenolic acids and terpenes known for their antioxidant and antimicrobial properties, for use as a food preservative. The antimicrobial and antioxidant activities were assessed through in vitro assays, revealing their potential for value-added applications in food preservation and therapeutic uses.

0

Introduction: Climate change poses various threats to marine life, particularly in shallow tropical waters. Objective: The impact of increased temperature and ultraviolet (UV) exposure on two photosymbiotic cnidarians, a common bubble-tip anemone and an upside-down jellyfish, was investigated. Methods: To illustrate the response of aquatic organisms, the metabolomes of unstressed Entacmaea quadricolor and Cassiopea andromeda were compared for detailed metabolite profiling. UHPLC-MS cou-pled with chemometrics and GNPS molecular networking was employed for sample classification and identification of markers unique to stress responses in each organism. Results: Several compounds with bioactive functions, including peptides and terpenoids, were reported for the first time in both organisms, viz. cyclic tetraglutamate, campestriene, and ceramide aminoethyl phosphonate (CEAP d18:2/16:0). Both anemone and jellyfish were subjected to either elevated UV-B light intensity up to 6.6 KJ m-2 or increased temperatures (28°C, 30°C, 32°C, and 34°C) over 4 days. Phospholipids, steroids, and ceramides emerged as chief markers of both types of stress, as revealed by the multivariate data analysis. Lysophosphatidylcholine (LPC 16:0), LPC (18:0/0:0), and echinoclasterol sulfate appeared as markers in both UV and thermal stress models of the anemone, whereas methyl/pro-pyl cholestane-hexa-ol were discriminatory in the UV stress model only. In the case of jellyfish, nonpolar glycosyl ceramide GlcCer (d14:1/28:6) served as a marker for UV stress, whereas polar peptides were ele-vated in the thermal stress model. Interestingly, both models of jellyfish share a phospholipid, lysophos-phatidylethanolamine (LPE 20:4), as a distinctive marker for stress, reported to be associated indirectly with the activity of innate immune response within other photosymbiotic Cnidaria such as corals and appears to be a fundamental stress response in marine organisms. Conclusion: This study presents several bioinformatic tools for the first time in two cnidarian organisms to provide not only a broader coverage of their metabolome but also broader insights into cnidarian bleaching in response to different stressors, i.e., heat and UV light, by comparing their effects in anemone versus jellyfish.

Reverse‐prenylated phenolic compounds are an abundant class of bioactive plant natural products. Hyperixanthone A, an inhibitor of multidrug‐resistant Staphylococcus aureus, is a polyprenylated xanthone carrying two forward geminal and one reverse prenyl group. Although prenyltransferases responsible for the forward prenylations were identified, the final reverse prenylation reaction remained elusive. No plant enzyme catalyzing reverse prenylation of an aromatic carbon has been described so far. Here we use metabolic profiling and transcriptomic information from Hypericum perforatum and H. sampsonii to identify homologous enzymes involved in the formation of reverse‐prenylated xanthones and characterize their functions using in vitro, in vivo, and in silico approaches. The identified enzymes are non‐canonical UbiA‐type prenyltransferases, which surprisingly catalyze both forward and reverse prenylations with different regioselectivities. Reconstruction of the enzyme cascade in Saccharomyces cerevisiae and Nicotiana benthamiana confirmed reverse‐prenylated hyperixanthone A as the major product. Molecular modeling and docking simulations supported by site‐directed mutagenesis suggest two distinct binding modes, which enable forward and reverse prenylations and provide a rationale for the preferred catalysis of the reverse prenyl transfer reaction. The identification of reverse prenylation augments the repertoire of reactions catalyzed by membrane‐bound UbiA‐type plant aromatic prenyltransferases. The insights also provide a new tool for the biotechnological modification of pharmaceutically valuable natural products.

The fungal sesquiterpene synthase BcBOT2 shows unique substrate promiscuity. It transforms farnesyl pyrophosphate (FPP) into presilphiperfolan-8β-ol via a cationic cascade that is initiated by a (1 → 11) cyclization. Here, it is shown that BcBOT2 also accepts (2,3-Z)-configured FPP derivatives, which provide terpenoids that result from an initial (1 → 6) cyclization. “Methyl mapping” was conducted by shifting the position of one or more methyl groups, and it was found that the location of methyl groups has a profound effect on the efficacy of cyclizations. In particular, the shift of the methyl group at C3 to the C2 position has the most profound effect on cyclohexane formation. Molecular modeling studies show that (1 → 6) cyclization took place due to adopting a different catalytically competent docking pose of FPP derivatives compared to natural FPP within the active site of the BcBOT2, which is mainly due to the (2,3-Z)-configuration. This docking pose leads to a C1−C6 distance shorter (3.3−3.5 Å) than the typical association with a near-attack conformation required for cyclization. Finally, these biotransformation results were benchmarked by a comprehensive study of the “hydrolysis” of eight different FPP derivatives. Under enzyme-free conditions, cyclohexene and cycloheptene terpenoids are formed. The ring size is mainly determined by the position of the methyl group at C6 or C7. The study reveals that in addition to protein engineering, unnatural substrates can also be used to specifically manipulate the mode of cyclization of terpene synthases.

Hyaloperonospora arabidopsidis (Hpa) is an oomycete pathogen that causes downy mildew disease on Arabidopsis. This obligate biotroph manipulates the homeostasis of its host plant by secreting numerous effector proteins, among which are the RxLR effectors. Identifying the host targets of effectors and understanding how their manipulation facilitates colonization of plants are key to improve plant resistance to pathogens. Here we characterize the interaction between the RxLR effector HaRxL106 and BIM1, an Arabidopsis transcription factor (TF) involved in Brassinosteroid (BR) signaling. We report that HaRxL106 interacts with BIM1 in vitro and in planta. BIM1 is required by the effector to increase the host plant susceptibility to (hemi)biotrophic pathogens, and thus can be regarded as a susceptibility factor. Mechanistically, HaRxL106 requires BIM1 to induce the transcriptional activation of BR‐responsive genes and cause alterations in plant growth patterns that phenocopy the shade avoidance syndrome. Our results support previous observations of antagonistic interactions between activation of BR signaling and suppression of plant immune responses and reveal that BIM1, a new player in this crosstalk, is manipulated by the pathogenic effector HaRxL106.

Suberin is a hydrophobic biopolymer that acts as an internal and external diffusion and transpiration barrier in plants. It is involved in two phases of wound healing, i.e. initial closing layer formation and subsequent wound periderm development. Transcriptomic and metabolomic analyses of wounded potato leaf tissue revealed preferential induction of cell wall modifying processes during closing layer formation, accompanied by a highly active defense response. To address the importance of suberin in this process, we generated loss of function mutants by CRISPR-Cas9 editing the suberin transporter gene StABCG1. Both wound-induced StABCG1 transcript levels and suberin formation around wounded leaf tissue were reduced in CRISPR-lines. Moreover, wound-induced tissue damage was characterized by browning of wound-adjacent areas. Transcriptome analyses of these areas revealed up-regulation of genes encoding defense proteins and enzymes of the phenylpropanoid pathway. Levels of hydroxycinnamic acid amides, acting in defense and in cell wall reinforcement, were drastically enhanced in CRISPR compared to control plants. These results suggest that the reduction in suberin formation around wounded tissue leads to a loss of barrier function, resulting in tissue browning due to enhanced exposure to oxygen.

Formaldehyde emerges as a cornerstone in multicomponent reactions, mainly prized for its robust reactivity. Yet, alongside these beneficial traits, this highly reactive C1-building block raises concerns, primarily regarding its toxicity. One notable issue is the challenge of controlling the formation of undesired byproducts during its reactions. This review explores alternative C1-building blocks that serve as surrogates for formaldehyde, aiming to mitigate some of the challenges associated with its use in multicomponent reactions. By identifying these alternatives, toxicity concerns and improved reaction control can be addressed, paving the way for more efficient and sustainable synthetic methodologies.

Two connected histopathological hallmarks of Alzheimer’s disease (AD) are chronic neuroinflammation and synaptic dysfunction. The accumulation of the most prevalent posttranslationally modified form of Aβ1–42, pyroglutamylated amyloid-β (Aβ3(pE)-42) in astrocytes is directly linked to glial activation and the release of proinflammatory cytokines that in turn contribute to early synaptic dysfunction in AD. At present, the mechanisms of Aβ3(pE)-42 uptake to astrocytes are unknown and pharmacological interventions that interfere with this process are not available. Here we developed a simple screening assay to identify substances from a plant extract library that prevent astroglial Aβ3(pE)-42 uptake. We first show that this approach yields valid and reproducible results. Second, we show endocytosis of Aβ3(pE)-42 oligomers by astrocytes and that quercetin, a plant flavonol, is effective to specifically block astrocytic buildup of oligomeric Aβ3(pE)-42. Importantly, quercetin does not induce a general impairment of endocytosis. However, it efficiently protects against early synaptic dysfunction following exogenous Aβ3(pE)-42 application.