Abstract 2378 Chloroplast acetyltransferases in regulation of photosynthesis

Plants are primary producers that harvest solar energy and convert it into chemical energy through photosynthesis. Photosynthetic light reactions are catalyzed by pigment-protein complexes located in the thylakoid membranes of the chloroplasts. The captured energy is stored in the form of ATP and NADPH, which are used in a number of metabolic processes including carbon assimilation. In nature, plants need to rapidly adjust photosynthetic reactions according to constantly fluctuating environmental conditions, which can be achieved via various post-translational modifications of chloroplast proteins. In addition to phosphorylation, which has been known to be a major determinant for the dynamic harvesting of light energy (i.e. state transitions) already for decades, we have recently shown that the chloroplast-located acetyltransferase GNAT2 is involved in the regulation of light harvesting and also in the regulation of thylakoid ultrastructure 1,2. As the gnat2 knock-out mutant shows defects in both lysine and N-terminal acetylation of chloroplast proteins, it is plausible that acetylation plays a major in the regulation photosynthetic reactions. The detailed role of GNAT2 and other seven recently identified chloroplast acetyltransferases will be discussed 3,4. ________ Koskela M.M., Brünje A., Ivanauskaite A., Grabsztunowicz M., Lassowskat I., Neumann U., Dinh T.V., Sindlinger J., Schwarzer D., Wirtz M., Tyystjärvi E., Finkemeier I. and Mulo P. Plant Cell, 2018; 30: 1695-1709. Rantala M., Ivanauskaite A., Laihonen L., Kanna S.D., Ughy B. and Mulo P. Plant and Cell Physiology, 2022; 63: 1205-1214. Bienvenut, W. V, Brünje, A., Boyer, J., Mühlenbeck, J. S., Bernal, G., Lassowskat, I., Dian, C., Linster, E., Dinh, T. V, Koskela, M. M., Jung, V., Seidel, J., Schyrba, L. K., Ivanauskaite, A., Eirich, J., Hell, R., Schwarzer, D., Mulo, P., Wirtz, M., Meinnel, T., Giglione, C., and Finkemeier, I.Molecular Systems Biology, 2020; 16, 1–23. Ivanauskaite A., Rantala M., Laihonen L., Konert M.M., Schwenner N., Mühlenbeck J., Finkemeier I. and Mulo P. 2023; 64: 549-563.