Protein acetylation is a key co- and post-translational modification. How different types of acetylation respond to environmental stress is still unknown. GNAT2, a member of the newly discovered family of plastid acetyltransferases in plants, which is featuring both lysine- and N-terminal acetyltransferase activities, was used to obtain a holistic multi-omics acetylation-dependent view of the acclimation of plants to short-term light changes.
We utilized mass spectrometry-based proteomic and acetylation analysis to investigate the plants" responses to changes in light intensity. We grew WT and gnat2 plants under the same conditions and subjected them to high light, darkness, or standard growth conditions for two hours. To analyse the protein abundance and acetylation changes, we used quantitative mass spectrometry, which allowed the quantification of 5,620 protein groups in total. The analysis revealed that both WT and gnat2 plants showed a strong accumulation of heat shock family proteins under high light conditions. The proteomic analysis also showed that two proteins involved in oxidative stress tolerance, were found up-regulated in the WT upon high light stress but not in the gnat2 mutant.
The acetylome analysis showed that plastid NTA yield did not significantly change under different light conditions. However, the gnat2 mutant displayed downregulation of transcripts involved in translation-related pathways under darkness, suggesting that GNAT2 might be involved in the light-dependent control of translation.
The acetylome analysis revealed that the two different types of acetylations, catalyzed by GNAT2 in the chloroplast, distinctively respond to short-term changes in light conditions. The gnat2 mutant showed a more pronounced de-regulation in the lysine acetylome under high light treatment, with 50 acK sites up-regulated and only nine acK sites also significantly up-regulated in the WT.
In conclusion, our study highlights the unique strategies of plant acclimation to different light treatments involving specific protein modifications and suggests that plastid K- and N-terminal acetylations may respond differently to environmental or developmental stimuli. The research provides valuable insights into the plant's responses to changes in light intensity and the interplay between genetic and environmental factors, with a particular focus on mass spectrometry-based proteomic and acetylome analysis.