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KatNat_Elucidating the multifaceted functions of protein acetyltransferases in plant stress response and regulation of metabolism.

Subject Area Plant Physiology
Plant Biochemistry and Biophysics
Term from 2018 to 2022
Project identifier Deutsche Forschungsgemeinschaft (DFG) - Project number 353859218
 
Final Report Year 2022

Final Report Abstract

Plants have to coordinate their development and growth with a highly dynamic environment. They must constantly respond to a wide range of changes in environmental conditions, including stresses, such as high light, heat, drought, or salt in the soil. Such acclimation processes can be achieved through chemical modifications of proteins, allowing flexible and rapid changes in protein functions to alter cellular and physiological outputs. Protein acetylation is one such modification, which occurs on the N-termini (Nt) and internal lysine residues (K) of many proteins. Despite its prevalence, and in contrast to other well-studied modifications such as phosphorylation, our knowledge of: (i) the regulation, specificity, and plasticity of protein acetylation, and (ii) its downstream functional consequences on protein activity and physiology are severely lacking, especially in plants. This ERA-CAPS consortium focused on the multifaceted functions of protein acetylation in different sub-cellular compartments. The main aim of the KatNat project was to provide a mechanistic understanding of protein acetylation in plants, with a particular focus on investigating the enzymes that catalyze this modification (Nt- and K-acetyltransferases) and the resultant effects on proteostasis, photosynthesis, and metabolism. The KatNat project consisted of four interrelated objectives to shed new light on the questions: (1) How does abiotic stress regulate the global Nt- and K-acetylome?; (2) What are the specificities, targets and stress-responsive dynamics of the acetyltransferases?; (3) How does protein acetylation impact protein stability and turnover?; (4) How does protein acetylation in plastids regulate photosynthesis and metabolism? Important discoveries have been made in all four objectives. For the cytosolic acetyltransferases, we discovered that the Arabidopsis NAA50 enzyme displayed mainly N-terminal next to some residual lysine acetyltransferase activity. Defects in NAA50 expression resulted in severe growth retardation and infertility and caused the accumulation of proteins involved in stress responses. Similarly, loss-of-function mutants of the plasma membrane-anchored N-acetyltransferase NAA60 revealed its importance during high salt stress. In addition, we discovered a new family of plastid N-acetyltransferases, which consist out of eight members, which possess dual lysine and N-terminal acetylation activities (Bienvenut et al.2020 Mol Sys Biol). We identified the protein substrates of these enzymes and revealed that GNAT2 is required for photosynthetic state transitions in Arabidopsis. The here identified novel roles of the plant N-acetyltransferase machinery in development and stress responses changed the view on N-terminal acetylation in plastids and cytosol of plant cells. While the KatNat projects made important new discoveries in the field of protein acetylation research and its importance for plant acclimation responses, several new questions arose from our work, such as to what extend the plastid GNATs have redundant functions and how their activity is regulated. These new questions will need to be addressed in future research.

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