ORCID Profile
0000-0003-0796-8308
Current Organisations
University of Oxford
,
Westfälische Wilhelms-Universität Münster
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Publisher: Cold Spring Harbor Laboratory
Date: 29-04-2020
DOI: 10.1101/2020.04.28.065441
Abstract: Malate is the major substrate for respiratory oxidative phosphorylation in illuminated leaves. In the mitochondria malate is converted to citrate either for replenishing tricarboxylic acid (TCA) cycle with carbon, or to be exported as substrate for cytosolic biosynthetic pathways or for storage in the vacuole. In this study, we show that DIC2 functions as a mitochondrial malate/citrate carrier in vivo in Arabidopsis. DIC2 knockout ( dic2-1 ) results in growth retardation that can only be restored by expressing DIC2 but not its closest homologs DIC1 or DIC3, indicating that their substrate preferences are not identical. Malate uptake by non-energised dic2-1 mitochondria is reduced but can be restored in fully energised mitochondria by altering fumarate and pyruvate/oxaloacetate transport. A reduced citrate export but an increased citrate accumulation in substrate-fed, energised dic2-1 mitochondria suggest that DIC2 facilitates the export of citrate from the matrix. Consistent with this, metabolic defects in response to a sudden dark shift or prolonged darkness could be observed in d ic2-1 leaves, including altered malate, citrate and 2-oxoglutarate utilisation. There was no alteration in TCA cycle metabolite pools and NAD redox state at night however, isotopic glucose tracing reveals a reduction in citrate labelling in dic2-1 which resulted in a ersion of flux towards glutamine, as well as the removal of excess malate via asparagine and threonine synthesis. Overall, these observations indicate that DIC2 is responsible in vivo for mitochondrial malate import and citrate export which coordinate carbon metabolism between the mitochondrial matrix and the other cell compartments. Mitochondria are pivotal for plant metabolism. One of their central functions is to provide carbon intermediates for the synthesis of critical building blocks, such as amino acids. Malate import and citrate export are two of the most recognised and specialised features of the mitochondrial role in the plant cellular metabolic network, yet the possibility that a single carrier would unite both functions has not been considered. Here, we have demonstrated that DIC2 preferentially fulfils these two functions in Arabidopsis thaliana in vivo , making it a bifunctional gateway for two major metabolite fluxes into and out of the mitochondrial matrix in the plant cell. Our results highlight the significance of DIC2 in cooperation with other mitochondrial carriers in maintaining metabolic balance even under challenging environmental conditions.
Publisher: Elsevier BV
Date: 08-2012
Publisher: Oxford University Press (OUP)
Date: 11-10-2023
Publisher: Oxford University Press (OUP)
Date: 28-03-2016
DOI: 10.1104/PP.16.00166
Publisher: Elsevier BV
Date: 11-2014
DOI: 10.1016/J.MITO.2014.02.006
Abstract: The mitochondrial NADH dehydrogenase complex (complex I) of the respiratory chain has several remarkable features in plants: (i) particularly many of its subunits are encoded by the mitochondrial genome, (ii) its mitochondrial transcripts undergo extensive maturation processes (e.g. RNA editing, trans-splicing), (iii) its assembly follows unique routes, (iv) it includes an additional functional domain which contains carbonic anhydrases and (v) it is, indirectly, involved in photosynthesis. Comprising about 50 distinct protein subunits, complex I of plants is very large. However, an even larger number of proteins are required to synthesize these subunits and assemble the enzyme complex. This review aims to follow the complete "life cycle" of plant complex I from various molecular perspectives. We provide arguments that complex I represents an ideal model system for studying the interplay of respiration and photosynthesis, the cooperation of mitochondria and the nucleus during organelle biogenesis and the evolution of the mitochondrial oxidative phosphorylation system.
Publisher: Cold Spring Harbor Laboratory
Date: 08-05-2023
DOI: 10.1101/2023.05.06.539686
Abstract: Mitochondria act as cellular hubs of energy transformation and metabolite conversion in most eukaryotes. Plant mitochondrial electron transport chains are particularly flexible, featuring alternative components, such as ALTERNATIVE NAD(P)H DEHYDROGENASES and ALTERNATIVE OXIDASES (AOXs), that can bypass proton translocation steps. PLANT UNCOUPLING MITOCHONDRIAL PROTEINS (named PUMPs or plant UCPs) have been identified in plants as homologues of mammalian Uncoupling Proteins (UCPs), and their biochemical and physiological roles have been investigated in the context of mitochondrial energy metabolism. To dissect UCP function in Arabidopsis, the two most conserved (UCP1 and UCP2) have been targeted in recent work by combining mutant lines to circumvent potential functional redundancy in vivo . Such approaches rely on the assumption that both proteins reside in the inner mitochondrial membrane as a prerequisite for functional redundancy. Yet, contradicting results have been reported on UCP2 localization in plants. Here we provide evidence that, conversely to UCP1, which is an abundant inner mitochondrial membrane protein, UCP2 localizes to the Golgi rather than to mitochondria. Based on multiple lines of new and prior evidence, we summarize the consensus view that we have reached and provide an ex le of how open, critical exchange within the research community is able to constructively address ambiguities. Our observations and considerations provide direction to the ongoing discussion about the functions of UCP proteins. They further offer new perspectives for the study of Golgi membrane transport and subcellular targeting principles of membrane proteins. Since 20 to 30 % of genes in plant genomes are predicted to encode transmembrane proteins and the function of most of those proteins has not been experimentally investigated, we highlight the importance of using independent evidence for localization as a prerequisite for understanding physiological function of membrane proteins.
Publisher: Wiley
Date: 03-11-2020
DOI: 10.1111/TPJ.14534
Abstract: Mitochondria host vital cellular functions, including oxidative phosphorylation and co-factor biosynthesis, which are reflected in their proteome. At the cellular level plant mitochondria are organized into hundreds of discrete functional entities, which undergo dynamic fission and fusion. It is the in idual organelle that operates in the living cell, yet biochemical and physiological assessments have exclusively focused on the characteristics of large populations of mitochondria. Here, we explore the protein composition of an in idual average plant mitochondrion to deduce principles of functional and structural organisation. We perform proteomics on purified mitochondria from cultured heterotrophic Arabidopsis cells with intensity-based absolute quantification and scale the dataset to the single organelle based on criteria that are justified by experimental evidence and theoretical considerations. We estimate that a total of 1.4 million protein molecules make up a single Arabidopsis mitochondrion on average. Copy numbers of the in idual proteins span five orders of magnitude, ranging from >40 000 for Voltage-Dependent Anion Channel 1 to sub-stoichiometric copy numbers, i.e. less than a single copy per single mitochondrion, for several pentatricopeptide repeat proteins that modify mitochondrial transcripts. For our analysis, we consider the physical and chemical constraints of the single organelle and discuss prominent features of mitochondrial architecture, protein biogenesis, oxidative phosphorylation, metabolism, antioxidant defence, genome maintenance, gene expression, and dynamics. While assessing the limitations of our considerations, we exemplify how our understanding of biochemical function and structural organization of plant mitochondria can be connected in order to obtain global and specific insights into how organelles work.
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for Markus Schwarzländer.