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…
Inorganic phosphate (Pi) is often a limiting plant nutrient. In members of the Brassicaceae family, such as Arabidopsis (Arabidopsis thaliana), Pi deprivation reshapes root system architecture to favor topsoil foraging. It does so by inhibiting primary root extension and stimulating lateral root formation. Root growth inhibition from phosphate (Pi) deficiency is triggered by iron-stimulated, apoplastic reactive oxygen species generation and cell wall modifications, which impair cell-to-cell communication and meristem maintenance. These processes require LOW PHOSPHATE RESPONSE1 (LPR1), a cell wall-targeted ferroxidase, and PHOSPHATE DEFICIENCY RESPONSE2 (PDR2), the single endoplasmic reticulum (ER)-resident P5-type ATPase (AtP5A), which is thought to control LPR1 secretion or activity. Autophagy is a conserved process involving the vacuolar degradation of cellular components. While the function of autophagy is well established under nutrient starvation (C, N, or S), it remains to be explored under Pi deprivation. Because AtP5A/PDR2 likely functions in the ER stress response, we analyzed the effect of Pi limitation on autophagy. Our comparative study of mutants defective in the local Pi deficiency response, ER stress response, and autophagy demonstrated that ER stress-dependent autophagy is rapidly activated as part of the developmental root response to Pi limitation and requires the genetic PDR2-LPR1 module. We conclude that Pi-dependent activation of autophagy in the root apex is a consequence of local Pi sensing and the associated ER stress response, rather than a means for systemic recycling of the macronutrient.
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.