Dear colleagues,

Biology Thursday seminar continues 11th April at 3pm, on site in room SÄ110 - please note unusual time and room!

Our speaker will be Prof. Paula Mulo from the University of Turku, on "New insights into regulation of photosynthesis: Chloroplast acetyltransferases and acetylation of chloroplast proteins" (abstract below)

More on her research at: https://www.utu.fi/fi/ihmiset/paula-mulo

Also remember that Prof. Mulo will be the opponent for Nga Nguyen's thesis defence on Friday 12th, at noon: https://www.oulu.fi/en/theses/towards-comprehensive-understanding-fruit-deve...

See you in the seminar,

Heikki

New insights into regulation of photosynthesis: Chloroplast acetyltransferases and acetylation of chloroplast proteins

Paula Mulo

Department of Life Technologies, University of Turku, 20520 Turku, Finland

pmulo@utu.fimailto:pmulo@utu.fi

Acetylation is one of the most common chemical modifications, and it affects a variety of molecules ranging from metabolites to proteins. Recent development of enrichment techniques and mass spectrometry has revealed that acetylation is a prevalent modification also in plants, and that in addition to cytosolic and nuclear proteins also numerous chloroplast proteins are targets of N-terminal and/or lysine acetylation. We have recently characterized a chloroplasts-localized family of GNAT acetyltransferases in Arabidopsis thaliana. The GNAT enzymes are unique among the acetyltransferase enzymes as they possess dual protein acetylation activity, i.e. they catalyze acetylation of the N-terminal amino acid as well as acetylation of the integral lysine residues of the protein. Our results show that each GNAT enzyme has distinct specificity in terms of favored substrates, and that they play unique roles in the accumulation of specific plant metabolites. Depletion of GNAT2 has marked effects on the acetylation level of several chloroplast proteins, organization of thylakoid protein complexes and photosynthetic properties of plants. Specifically, formation of the Photosystem I-LHCII complex is prevented in the gnat2 knock-out plants, which results in impaired balancing of the light energy between the photosystems (state transitions). Moreover, loss of GNAT2 severely disturbs light-dependent dynamics of thylakoid stacking. Altogether, our results indicate that chloroplast acetyltransferases are new and important regulators of photosynthetic light harvesting with a marked impact on the growth and metabolism of plants.

Koskela et al. 2018 Plant Cell 30, 1695-1709; Bienvenut et al. 2020 Mol Syst Biol 16:e9464; Koskela et al. 2020 Photosynth Res, 145, 15-30; Rantala et al. 2022 Plant Cell Physiol 63,1205-1214; Ivanauskaite et al. 2023 Plant Cell Physiol 64, 549-563.