Exploring the Roles of Chloroplast GNATs: Acetylation as a Regulatory Mechanism in Photosynthesis and Senescence – AcetylPlast

The AcetylPlast project, based on a long-standing French-German collaboration, aims to unravel the complex roles of N-terminal acetylation (NTA) and lysine acetylation (KAT) in plastids. A key discovery by our consortium is the identification of a unique family of plastid GNAT (Gcn5-related N-acetyltransferase) enzymes with dual NTA and KAT activities. Among them, GNAT2 has emerged as key regulator of photosynthesis, with its lysine acetylome, rather than its NTA acetylome, responding to light changes, allowing plants to swiftly adapt to environmental fluctuations. Despite this progress, the need for a compartmentalized N-terminal modification system in photosynthetic organisms remain largely elusive.
Our preliminary results suggest that several GNATs may localize in plastid biocondensates, potentially creating localized protein modification hotspots, and may play a role in both plastid biogenesis and degradation during senescence.
AcetylPlast will investigate how GNAT dual modifications regulate plastid development and photosynthesis. Special focus is placed on the impact of acetylation on key targets such as RuBisCO or the cold tolerance factor CP29A. We will also examine the role of protein acetylation in environmental responses and phase separation processes, investigating how acetylation itself might be a compartmentalized process.
The project’s three main objectives are: 1) characterizing plastid GNATs in plastid biogenesis and senescence, 2) elucidating N-terminal modifications in RuBisCO maturation and CO2 fixation, and 3) exploring GNAT and HDAC roles in plastid biocondensate formation and dynamic during plant acclimation responses.
To achieve these goals, we will use in vitro and in vivo phase separation analyses, super-resolution microscopy, and advanced proteomic. AcetylPlast project aims to enhance our understanding of plant acclimation mechanisms and contribute to improvements in plant productivity and CO2 fixation efficiency.