Sensing and retrograde signaling of mitochondrial metabolic states in plants
Final Report Abstract
This Emmy Noether project initially focused on the investigation of a metabolite-dependent mitochondrial retrograde signaling pathway in the model plant species Arabidopsis thaliana. In particular, the tricarboxylic acid (TCA)-dependent signaling pathway was dissected to identify important key players and regulatory mechanisms, which might play a role in mitochondrial signaling. Our results demonstrated that particularly citrate, but not downstream metabolites, can be perceived in Arabidopsis leaves and induce a specific transcriptome response, which is similar to those of biotic stress treatments. Furthermore, we found out that the TCA cycle enzyme citrate synthase is sensitive to oxidation, and we identified the corresponding redox-sensitive cysteine residues. Since citrate is produced from acetyl-Coenzyme A, we focused on the development of new techniques for the investigation of the post-translational modification of lysine residues by acetylation. Together with the group of Steven C. Huber (University of Illinois), we were the first who extensively mapped this modification in plants and studied its impact on metabolic enzyme activities in in vitro experiments. It was particularly striking to observe that the activity of the Calvin-Benson cycle enzyme RuBisCO was increased by 40 % after in vitro deacetylation. Before our two studies, lysine acetylation in plants was mainly investigated in the context of chromatin regulation of histones. Since this line of research opened up a new field, we decided to shift our focus and to study the impact of this modification in mitochondria in more detail. We found out that lysine acetylation occurs within the mitochondrial matrix, is pH–dependent, and can be found on proteins within the respiratory complexes. We identified the first mitochondrial plant deacetylase, sirtuin 2. We showed that sirtuin 2 is an active deacetylase and interacts with the mitochondrial ATP/ADP carriers, which show an increase in lysine acetylation and an increased activity in the srt2 loss-of-function mutants. Hence, with sirtuin 2 we identified a novel key regulatory mitochondrial protein involved in metabolic regulation. With the development of a new mass spectrometry-based stable-isotope labeling technique for the relative quantification of lysine acetylation in plants, we are now able to dissect the regulation and targets of this modification in detail in several new lines of research which emanated from our studies.
Publications
- (2011) Proteins of diverse function and subcellular location are lysine-acetylated in Arabidopsis. Plant Physiology, 155(4):1779-1790
Finkemeier I, Laxa M, Miguet L, Howden AJM, Sweetlove L
- (2012) Plant mitochondrial retrograde signalling: posttranslational modifications enter the stage. Frontiers in Plant Sciences 3:253
Hartl M, Finkemeier I
(See online at https://doi.org/10.3389/fpls.2012.00253) - (2012) The impact of impaired mitochondrial function on retrograde signalling: a meta-analysis of transcriptomic responses. Journal of Experimental Botany, 63(4):1735-1750
Schwarzländer M, König AC, Sweetlove LJ, Finkemeier I
(See online at https://doi.org/10.1093/jxb/err374) - (2013) Mitochondrial energy and redox signaling in plants, Antioxidants and Redox Signaling, 18 (16), 2122-2144
Schwarzländer M, Finkemeier I
- (2013) The role of carboxylic acids in metabolite signaling in Arabidopsis leaves. Plant Physiology, 162 (1), 239-253
Finkemeier I, König AC, Heard W, Nunes Nesi A, Pham PA, Leister D, Fernie AR, Sweetlove LJ
- (2014) Redox regulation of Arabidopsis mitochondrial citrate synthase. Molecular Plant, 7 (1),156-169
Schmidtmann E, König AC, Orwat A, Leister D, Hartl M, Finkemeier I
(See online at https://doi.org/10.1093/mp/sst144) - (2014) The Arabidopsis class II sirtuin is a lysine deacetylase and interacts with mitochondrial energy metabolism. Plant Physiology 164: 1401-1414
König AC, Hartl M, Pham PA, Laxa M, Boersema P, Orwat A, Kalitventseva I, Plöchinger M, Braun HP, Leister D, Mann M, Wachter A, Fernie A, Finkemeier I
(See online at https://doi.org/10.1104/pp.113.232496) - (2014) The mitochondrial lysine acetylome of Arabidopsis. Mitochondrion 19: 252–260
König AC, Hartl M, Boersema PJ, Mann M, Finkemeier I
(See online at https://doi.org/10.1016/j.mito.2014.03.004) - (2015) Identification of lysine-acetylated mitochondrial proteins and their acetylation sites. Methods Mol Biol. 1305:107-21
Hartl M, König AC, Finkemeier I
(See online at https://doi.org/10.1007/978-1-4939-2639-8_7) - (2016) Lysine acetylation in mitochondria: From inventory to function. Mitochondrion
Hosp F, Lassowskat I, Santoro V, De Vleesschauwer D, Fliegner D, Redestig H, Mann M, Christian S, Hannah MA, Finkemeier I
(See online at https://doi.org/10.1016/j.mito.2016.07.012)
