Unser 10. Leibniz Plant Biochemistry Symposium am 7. und 8. Mai war ein großer Erfolg. Thematisch ging es in diesem Jahr um neue Methoden und Forschungsansätze der Naturstoffchemie. Die exzellenten Vorträge über Wirkstoffe…
Omanische Heilpflanze im Fokus der Phytochemie IPB-Wissenschaftler und Partner aus Dhofar haben jüngst die omanische Heilpflanze Terminalia dhofarica unter die phytochemische Lupe genommen. Die Pflanze ist reich an…
Geschmack ist vorhersagbar: Mit FlavorMiner. FlavorMiner heißt das Tool, das IPB-Chemiker und Partner aus Kolumbien jüngst entwickelt haben. Das Programm kann, basierend auf maschinellem Lernen (KI), anhand der…
Bellstaedt, J.; Trenner, J.; Lippmann, R.; Poeschl, Y.; Zhang, X.; Friml, J.; Quint, M.; Delker, C.;A Mobile Auxin Signal Connects Temperature Sensing in Cotyledons with Growth Responses in HypocotylsPlant Physiol.180757-766(2019)DOI: 10.1104/pp.18.01377
Plants have a remarkable capacity to adjust their growth and development to elevated ambient temperatures. Increased elongation growth of roots, hypocotyls, and petioles in warm temperatures are hallmarks of seedling thermomorphogenesis. In the last decade, significant progress has been made to identify the molecular signaling components regulating these growth responses. Increased ambient temperature utilizes diverse components of the light sensing and signal transduction network to trigger growth adjustments. However, it remains unknown whether temperature sensing and responses are universal processes that occur uniformly in all plant organs. Alternatively, temperature sensing may be confined to specific tissues or organs, which would require a systemic signal that mediates responses in distal parts of the plant. Here, we show that Arabidopsis (Arabidopsis thaliana) seedlings show organ-specific transcriptome responses to elevated temperatures and that thermomorphogenesis involves both autonomous and organ-interdependent temperature sensing and signaling. Seedling roots can sense and respond to temperature in a shoot-independent manner, whereas shoot temperature responses require both local and systemic processes. The induction of cell elongation in hypocotyls requires temperature sensing in cotyledons, followed by the generation of a mobile auxin signal. Subsequently, auxin travels to the hypocotyl, where it triggers local brassinosteroid-induced cell elongation in seedling stems, which depends upon a distinct, permissive temperature sensor in the hypocotyl.
Publikation
Goslin, K.; Eschen-Lippold, L.; Naumann, C.; Linster, E.; Sorel, M.; Klecker, M.; de Marchi, R.; Kind, A.; Wirtz, M.; Lee, J.; Rajjou, L.; Graciet, E.;Differential N-end Rule Degradation of RIN4/NOI Fragments Generated by the AvrRpt2 Effector ProteasePlant Physiol.1802272-2289(2019)DOI: 10.1104/pp.19.00251
In plants, the protein RPM1-INTERACTING PROTEIN4 (RIN4) is a central regulator of both pattern-triggered immunity and effector-triggered immunity. RIN4 is targeted by several effectors, including the Pseudomonas syringae protease effector AvrRpt2. Cleavage of RIN4 by AvrRpt2 generates potentially unstable RIN4 fragments, whose degradation leads to the activation of the resistance protein RESISTANT TO P. SYRINGAE2. Hence, identifying the determinants of RIN4 degradation is key to understanding RESISTANT TO P. SYRINGAE2–mediated effector-triggered immunity, as well as virulence functions of AvrRpt2. In addition to RIN4, AvrRpt2 cleaves host proteins from the nitrate-induced (NOI) domain family. Although cleavage of NOI domain proteins by AvrRpt2 may contribute to pattern-triggered immunity regulation, the (in)stability of these proteolytic fragments and the determinants regulating their stability remain unexamined. Notably, a common feature of RIN4, and of many NOI domain protein fragments generated by AvrRpt2 cleavage, is the exposure of a new N-terminal residue that is destabilizing according to the N-end rule. Using antibodies raised against endogenous RIN4, we show that the destabilization of AvrRpt2-cleaved RIN4 fragments is independent of the N-end rule pathway (recently renamed the N-degron pathway). By contrast, several NOI domain protein fragments are genuine substrates of the N-degron pathway. The discovery of this set of substrates considerably expands the number of known proteins targeted for degradation by this ubiquitin-dependent pathway in plants. These results advance our current understanding of the role of AvrRpt2 in promoting bacterial virulence.
Publikation
Faden, F.; Mielke, S.; Rajjou, L.;Modulating Protein Stability to Switch Toxic Protein Function On and Off in Living CellsPlant Physiol.179929-942(2019)DOI: 10.1104/pp.18.01215
Toxic proteins are prime targets for molecular farming (the generation of pharmacologically active or biotechnologically usable compounds in plants) and are also efficient tools for targeted cell ablation in genetics, developmental biology, and biotechnology. However, achieving conditional activity of cytotoxins and maintaining the toxin-expressing plants as stably transformed lines remain challenging. Here, we produce a switchable version of the highly cytotoxic bacterial RNase barnase by fusing the protein to a portable protein degradation cassette, the low-temperature degron cassette. This method allows conditional genetics based on conditional protein degradation via the N-end rule or N-degron pathway and has been used to vice versa accumulate and/or deplete a diverse variety of highly active, unstable or stable target proteins in different living multicellular organisms and cell systems. Moreover, we expressed the barnase fusion under control of the trichome-specific TRIPTYCHON promoter. This enabled efficient temperature-dependent control of protein accumulation in Arabidopsis (Arabidopsis thaliana) leaf hairs (trichomes). By tuning the levels of the protein, we were able to control the fate of trichomes in vivo. The on-demand formation of trichomes through manipulating the balance between stabilization and destabilization of barnase provides proof of concept for a robust and powerful tool for conditional switchable cell arrest. We present this tool as a potential strategy for the manufacture and accumulation of cytotoxic proteins and toxic high-value products in plants or for conditional genetic cell ablation.
Publikation
Matamoros, M. A.; Kim, A.; Peñuelas, M.; Ihling, C.; Griesser, E.; Hoffmann, R.; Fedorova, M.; Frolov, A.; Becana, M.;Protein Carbonylation and Glycation in Legume NodulesPlant Physiol.1771510-1528(2018)DOI: 10.1104/pp.18.00533
Nitrogen fixation is an agronomically and environmentally important process catalyzed by bacterial nitrogenase within legume root nodules. These unique symbiotic organs have high metabolic rates and produce large amounts of reactive oxygen species that may modify proteins irreversibly. Here, we examined two types of oxidative posttranslational modifications of nodule proteins: carbonylation, which occurs by direct oxidation of certain amino acids or by interaction with reactive aldehydes arising from cell membrane lipid peroxides; and glycation, which results from the reaction of Lys and Arg residues with reducing sugars or their auto-oxidation products. We used a strategy based on the enrichment of carbonylated peptides by affinity chromatography followed by liquid chromatography-tandem mass spectrometry to identify 369 oxidized proteins in bean (Phaseolus vulgaris) nodules. Of these, 238 corresponded to plant proteins and 131 to bacterial proteins. Lipid peroxidation products induced most carbonylation sites. This study also revealed that carbonylation has major effects on two key nodule proteins. Metal-catalyzed oxidation caused inactivation of malate dehydrogenase and aggregation of leghemoglobin. In addition, numerous glycated proteins were identified in vivo, including three key nodule proteins: sucrose synthase, glutamine synthetase, and glutamate synthase. Label-free quantification identified 10 plant proteins and 18 bacterial proteins as age-specifically glycated. Overall, our results suggest that the selective carbonylation or glycation of crucial proteins involved in nitrogen metabolism, transcriptional regulation, and signaling may constitute a mechanism to control cell metabolism and nodule senescence.