Phosphorylation events controlling low oxygen-signaling in Arabidopsis thaliana

• Applicant: Professor Dr. Joost T. van Dongen
• Subject Area: Plant Physiology
• Term: from 2017 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 387214090

Plants exposed to low oxygen conditions, e.g. caused by flooding, show extensive reprogramming of their metabolism. First of all, aerobic respiration (using molecular oxygen) switches to anaerobic metabolism, which still ensures the production of energy equivalents in the form of ATP but with less efficiency. The induction of genes specific to hypoxic adaptation is under the control of transcription factors of the ETHYLENE RESPONSE FACTOR (ERF) family, of which group VII ERFs play a crucial role in this process. Their function is restricted to hypoxia by their oxygen-dependent dissociation from plasma membrane-localized ACYL-COA-BINDING PROTEINS (ACBPs) and subsequent translocation to the nucleus.We already demonstrated that acyl-CoAs, activated fatty acids, trigger translocation of ERFVIIs and showed that certain changes in the cellular acyl-CoA pool induce hypoxic responses. However, because hypoxia-induced changes of the acyl-CoA pool take up to three hours to occur, and acyl-CoA application can induce only mild responses in air as compared to gene induction observed under hypoxia, a second, parallel trigger operating independently of acyl-CoAs is essential for inducing translocation of ERFVIIs and modulating ERFVII activity.The aim of this proposal is to unravel the role of phosphorylation in (1) inducing translocation of ERFVIIs into the nucleus and (2) modulating activity of ERFVIIs in an oxygen-dependent manner. By exploring the impact of phosphorylation in ERFVII-dependent hypoxia signaling we will greatly extend our understanding of the integration of multiple signals under hypoxia with ACBP and ERFVIIs being the central interface.Our preliminary work using in vitro kinase activity assays, in vivo interaction studies, in planta phosphoproteomic analyses and transactivation assays indicates that phosphorylation of components of the ERFVII-dependent signaling cascade is important for both processes. Furthermore, we showed that low oxygen promotes phosphorylation of ACBPs in planta and could identify specific low oxygen-activated MITOGEN-ACTIVATED PROTEIN KINASES (MPKs), which target several components of the ERFVII signaling cascade. We intend to investigate how exactly the phosphorylation status of the signaling components impacts on their ability to interact, their activity and their contribution to low oxygen tolerance in planta. In addition, we want to study under which oxygen concentrations phosphorylation via MPKs occurs in planta. As these MPKs themselves are activated by reactive oxygen species (ROS) under low oxygen, we will investigate to which extend intracellular ROS sources contribute to the induction of the ERFVII signaling cascade. To this aim, we will conduct molecular biological, biochemical as well as genetic strategies.

• DFG Programme: Research Grants
• Co-Investigator: Professorin Dr. Romy Schmidt-Schippers