Florian Schindler

More than 200 years ago, Alexander von Humboldt described a tree of the genus Clusia for its ability to perform crassulacean acid metabolism (CAM). This drought-adaptive metabolism allows plants to maintain photosynthesis under water limitation by temporally separating CO₂ uptake and fixation. The diversity of CAM physiotypes has fueled a debate about evolutionary constraints and the feasibility of engineering CAM into C₃ crops. The genus Clusia displays an exceptional diversity of photosynthetic physiotypes, yet genome sequences and genomic mechanisms generating this diversity remain unresolved. Here, we sequence and compare the genomes of three Clusia species spanning weak, inducible, and strong CAM. We show that polyploidization followed by transposon-mediated genic diploidization could have shaped CAM-related gene families, particularly those controlling phosphoenol-pyruvate recycling via phosphorolytic leaf starch metabolism. Our results indicate that whole-genome duplication coupled to diploidization might have driven diversification of CAM physiotypes in Clusia , providing a genomic framework for understanding CAM diversity and evolution.

Agricultural pests like parasitic broomrapes and witchweeds differentiate a haustorium that penetrates another plant’s root for nutrient acquisition. We demonstrate that during imbibition and postgermination growth, parasite seeds produce bioactive haustorium-inducing factors (HIFs) to differentiate their haustorium independently of host signals, thereby challenging the paradigm of host-induced haustoriogenesis. Metabolome profiling of this seed “leachate” unraveled synergistic haustoriogenic potential of possibly canonical HIF classes at hormonal concentrations, including cytokinins, sterols, quinones, and flavonoids. We suggest that early lignin neosynthesis serves as a template for HIF production through postgerminative oxidative stress and microbial ligninolytic activity. Seedlings with host-independently formed haustoria attached faster to and produced more tubercles on compatible hosts. Thus, haustorium differentiation via a coopted autonomous developmental program potentiates the eco-evolutionary success of obligate parasitic plants.

Palmitic acid-induced lipotoxicity contributes to the development of nonalcoholic fatty liver disease (NAFLD). Hesperetin has been reported to alleviate oxidative stress, inflammation, and cell death in NAFLD, while its potential to mitigate palmitic acid-induced lipotoxicity remains unexplored. This study investigates the protective effects of hesperetin on palmitic-acid-stimulated lipotoxicity and elucidates the underlying molecular mechanisms. Our results showed that hesperetin decreased palmitic acid-activated lipotoxicity through inhibition of the intrinsic apoptosis pathway and promotion of autophagic flux. Metabolomics analysis and stable-isotope-tracing data indicated that hesperetin treatment restored the aberrant tricarboxylic acid cycle caused by palmitic acid exposure, accompanied by a decrease in anaplerotic flux from glutamine to α-ketoglutarate. The reduction of α-ketoglutarate resulted in the inhibition of mTORC1 signaling, which in turn activated autophagy and limited apoptosis. Furthermore, hesperetin activated AMPK, which coordinated with mTORC1 to regulate autophagy. Additionally, hesperetin reinstated the activation of AKT and Nrf2, further protecting the cell against the deleterious effects of lipotoxicity. These data highlight the role of glutaminolysis as a survival mechanism for preventing lipotoxicity upon hesperetin treatment.

Summary: Excessive nitrogen use and low nitrogen use efficiency (NUE) in current agroecosystems are disrupting the global nitrogen cycle. Chemical inhibitors offer only temporary relief, while plant‐derived biological nitrification inhibitors (BNIs) remain safer but underexplored. Identifying biological nitrification inhibition (BNI) traits in nitrogen‐demanding crops like wheat is key to improving sustainability. In this study, a combined GC‐ and LC–MS platform was used to determine the metabolome of the root exudates of 44 diverse wheat genotypes originating from India and Austria. With more than 6000 metabolic features, a pronounced genotype‐specific variation, a clear geographic pattern and an unexpected complexity of the root exudate metabolome were observed. A novel high‐throughput assay utilizing diverse ammonia‐oxidizing bacteria (AOB) and archaea (AOA) was developed for rapid BNI testing, highlighting distinct inhibition and even growth stimulation capacities between genotypes. Network analysis and advanced machine and deep learning analysis identified combinations of 32 metabolites linked to high BNI activity, including phenylpropanoids sinapinic acid, syringic acid and others, as well as glycosylated flavones isoschaftoside and others. This indicates that the concurrent presence of specific metabolites, rather than a single compound, drives nitrification inhibition in the rhizosphere. Variation in BNI activity among wheat genotypes, classified as either spring or winter types, suggests that root architecture modulates the dynamics of root exudation and the potential for nitrification inhibition. The unique combination of high‐throughput metabolomics analysis and the BNI fast‐track assay allows for screening of large germplasm collections as an essential requirement to introduce BNI and related NUE traits into modern breeding programmes.

Deregulation of mitochondrial functions in hepatocytes contributes to many liver diseases, such as nonalcoholic fatty liver disease (NAFLD). Lately, it was referred to as MAFLD (metabolism-associated fatty liver disease). Hesperetin (Hst), a bioactive flavonoid constituent of citrus fruit, has been proven to attenuate NAFLD. However, a potential connection between its preventive activities and the modulation of mitochondrial functions remains unclear. Here, our results showed that Hst alleviates palmitic acid (PA)-triggered NLRP3 inflammasome activation and cell death by inhibition of mitochondrial impairment in HepG2 cells. Hst reinstates fatty acid oxidation (FAO) rates measured by seahorse extracellular flux analyzer and intracellular acetyl-CoA levels as well as intracellular tricarboxylic acid cycle metabolites levels including NADH and FADH₂ reduced by PA exposure. In addition, Hst protects HepG2 cells against PA-induced abnormal energetic profile, ATP generation reduction, overproduction of mitochondrial reactive oxygen species, and collapsed mitochondrial membrane potential. Furthermore, Hst improves the protein expression involved in PINK1/Parkin-mediated mitophagy. Our results demonstrate that it restores PA-impaired mitochondrial function and sustains cellular homeostasis due to the elevation of PINK1/Parkin-mediated mitophagy and the subsequent disposal of dysfunctional mitochondria. These results provide therapeutic potential for Hst utilization as an effective intervention against fatty liver disease.

Plant growth promoting bacteria can confer resistance to various types of stress and increase agricultural yields. The mechanisms they employ are diverse. One of the most important genes associated with the increase in plant biomass and stress resistance is acdS, which encodes a 1-aminocyclopropane-1-carboxylate- or ACC-deaminase. The non-proteinogenic amino acid ACC is the precursor and means of long-distance transport of ethylene, a plant hormone associated with growth arrest. Expression of acdS reduces stress induced ethylene levels and the enzyme is abundant in rhizosphere colonizers. Whether ACC hydrolysis plays a role in the phyllosphere, both as assembly cue and in growth promotion, remains unclear. Here we show that Paraburkholderia dioscoreae Msb3, a yam phyllosphere symbiont, colonizes the tomato phyllosphere and promotes plant growth by action of its ACC deaminase. We found that acdS is required for improved plant growth but not for efficient leaf colonization. Strain Msb3 readily proliferates on the leaf surface of tomato, only occasionally spreading to the leaf endosphere through stomata. The strain can also colonize the soil or medium around the roots but only spreads into the root if the plant is wounded. Our results indicate that the degradation of ACC is not just an important trait of plant growth promoting rhizobacteria but also one of leaf dwelling phyllosphere bacteria. Manipulation of the leaf microbiota by means of spray inoculation may be more easily achieved than that of the soil. Therefore, the application of ACC deaminase containing bacteria to the phyllosphere may be a promising strategy to increasing plant stress resistance, pathogen control, and harvest yields.

A novel bacterium, designated strain Msb3^T, was recently isolated from leaves of the yam family plant Dioscorea bulbifera (Dioscoreaceae). Phylogenetic analysis based on the 16S rRNA gene sequence indicated that this strain belonged to the genus Paraburkholderia with Paraburkholderia xenovorans as nearest validly named neighbour taxon (99.3 % sequence similarity towards the P. xenovorans type strain). Earlier genome sequence analysis revealed a genome of 8.35 Mb in size with a G+C content of 62.5 mol%, which was distributed over two chromosomes and three plasmids. Here, we confirm that strain Msb3^T represents a novel Paraburkholderia species. In silico DNA–DNA hybridization and average nucleotide identity (OrthoANIu) analyses towards P. xenovorans LB400^T yielded 58.4 % dDDH and 94.5 % orthoANIu. Phenotypic and metabolic characterization revealed growth at 15 °C on tryptic soy agar, growth in the presence of 1 % NaCl and the lack of assimilation of phenylacetic acid as distinctive features. Together, these data demonstrate that strain Msb3^T represents a novel species of the genus Paraburkholderia, for which we propose the name Paraburkholderia dioscoreae sp. nov. The type strain is Msb3^T (=LMG 31881^T, DSM 111632^T, CECT 30342^T).

Roots secrete a vast array of low molecular weight compounds into the soil broadly referred to as root exudates. It is a key mechanism by which plants and soil microbes interact in the rhizosphere. The effect of drought stress on the exudation process and composition is rarely studied, especially in cereal crops. This study focuses on comparative metabolic profiling of the exudates from sensitive and tolerant genotypes of pearl millet after a period of drought stress. We employed a combined platform of gas and liquid chromatography coupled to mass spectrometry to cover both primary and secondary metabolites. The results obtained demonstrate that both genotype and drought stress have a significant impact on the concentration and composition of root exudates. The complexity and function of these differential root exudates are discussed. To reveal the potential effect of root exudates on the soil microbial community after a period of drought stress, we also tested for biological nitrification inhibition (BNI) activity. The analysis revealed a genotype-dependent enhancement of BNI activity after a defined period of drought stress. In parallel, we observed a genotype-specific relation of elongated root growth and root exudation under drought stress. These data suggest that the drought stress-dependent change in root exudation can manipulate the microbial soil communities to adapt and survive under harsh conditions.