Biology subjects

Günther, J.

Publications and source records attributed to Günther, J..

4 recordsLinked to original sources

bioRxiv2025

Metabolic engineering of Barbarea vulgaris identifies β-amyrin synthase LUP5 as a determinant of saponin-mediated insect resistance

Plant-insect coevolution has been a major driver of specialized metabolite diversification, yet the genetic basis of natural variation in defensive chemistry remains poorly understood. The wild crucifer Barbarea vulgaris comprises two ecotypes, an insect-resistant G-type and a susceptible P-type, characterized by distinct triterpenoid saponin profiles. To investigate the causal relationship between saponin composition and insect resistance, we established a stable transformation system for B. vulgaris. Expression of the G-type {beta}-amyrin synthase gene LUP5 in the susceptible P-type conferred up to a 95% reduction in Plutella xylostella feeding, accompanied by increased accumulation of three hederagenin-derived monodesmosidic saponins. Comparison of LUP5 expression driven by its native promoter and by the constitutive 35S promoter revealed that the native promoter leads to increased hederagenin accumulation and is activated later in development, which may prevent early metabolic stress and allow coordinated expression of downstream pathway genes. In contrast, silencing of CYP72A552 by RNAi decreased total hederagenin levels by approximately 40% without affecting resistance, indicating threshold-dependent defense. Our results provide direct in planta evidence that LUP5 is a key determinant of natural variation in insect resistance in B. vulgaris, underscoring the pivotal role of the saponin backbone in herbivore deterrence. By linking promoter activity to metabolite structural diversity, this work provides mechanistic and conceptual insight into how plants coordinate specialized metabolism and defense.

plant biology↗

bioRxiv2025

FMO and CYP monooxygenase families determine the metabolic flux of hydroxylated tryptamine derivatives in barley (Hordum vulgare) following pathogen infection

To counteract pathogenic microorganisms, plants execute a complex resistance response that includes major metabolic reprogramming and production of bioactive defensive compounds. Barley (Hordeum vulgare) is a major cereal crop, but suffers significant yield losses due to pathogen attack every year. Here we use an untargeted metabolomic approach to assess the diversity and shifts in key barley metabolites produced in response to Pyrenophora teres f. teres infection, a hemibiotrophic fungal pathogen and causal agent of net blotch disease. Tryptophan-derived compounds, including tryptamine, serotonin, and a novel indole alkaloid - 2-oxo-tryptamine (2OT) - were among the most significantly induced and abundant compounds, with mass spectrometry imaging revealing that these metabolites accumulate at the site of infection. A transcriptomic approach identified a flavin-containing monooxygenase (FMO), which was functionally characterized as a 2-oxo-tryptamine synthase (2OTS). In addition, a cytochrome P450 (CYP71P10) was characterized as a tryptamine-5-hydroxylase, responsible for serotonin biosynthesis. These characterized genes are tightly co-expressed with genes involved in tryptophan biosynthesis and signify a major metabolic flux towards indolic compounds after infection, potentially serving as bioactive phytoalexins. Additional microbial interactions using a biotrophic fungus (Blumeria hordei; powdery mildew), a hemibiotrophic bacterium (Pseudomonas syringae), and alternative cultivars suggest that these pathways represent a generally activated resistance response in barley. These results provide new insights within the barley defense response relevant for the development of disease resistant traits in cereal crops.

plant biology↗

bioRxiv2020

Discovery of a hidden transient state in all bromodomain families

Bromodomains (BDs) are small protein modules that interact with acetylated marks in histones. These post-translational modifications are pivotal to regulate gene expression, making BDs promising targets to treat several diseases. While the general structure of BDs is well known, their dynamical features and their interplay with other macromolecules are poorly understood, hampering the rational design of potent and selective inhibitors. Here we combine extensive molecular dynamics simulations, Markov state modeling and structural data to reveal a novel and transiently formed state that is conserved across all BD families. It involves the breaking of two backbone hydrogen bonds that anchor the ZA-loop with the A helix, opening a cryptic pocket that partially occludes the one associated with histone binding. Our results suggest that this novel state is an allosteric regulatory switch for BDs, potentially related to a recently unveiled BD-DNA binding mode.

biophysics↗

bioRxiv2018

All four double-stranded RNA binding domains of Staufen2 contribute to efficient mRNA recognition and transcript localization

Throughout metazoans, Staufen (Stau) proteins are core factors of mRNA localization particles. They consist of three to four double-stranded RNA binding domains (dsRBDs) and a C-terminal dsRBD-like domain. Mouse Staufen2 (mStau2) like Drosophila Stau (dmStau) contains four dsRBDs. Existing data suggest that only dsRBDs 3-4 are necessary and sufficient for mRNA binding. Here, we show that dsRBDs 1 and 2 of mStau2 bind RNA with similar affinities and kinetics as dsRBDs 3 and 4. While RNA binding by these tandem domains is transient, all four dsRBDs recognize their target RNAs with high stability. Rescue experiments in Drosophila oocytes demonstrate that mStau2 partially rescues dmStau-dependent mRNA localization. In contrast, a rescue with mStau2 bearing RNA-binding mutations in dsRBD1-2 fails, confirming the physiological relevance of our findings. In summary, our data show that the dsRBDs 1-2 play essential roles in the mRNA recognition and function of Stau- family proteins of different species.

biochemistry↗