TY - JOUR

T1 - The function of glutaredoxin GRXS15 is required for lipoyl-dependent dehydrogenases in mitochondria

AU - Moseler, Anna

AU - Kruse, Inga

AU - Maclean, Andrew E

AU - Pedroletti, Luca

AU - Franceschetti, Marina

AU - Wagner, Stephan

AU - Wehler, Regina

AU - Fischer-Schrader, Katrin

AU - Poschet, Gernot

AU - Wirtz, Markus

AU - Dörmann, Peter

AU - Hildebrandt, Tatjana M

AU - Hell, Rüdiger

AU - Schwarzländer, Markus

AU - Balk, Janneke

AU - Meyer, Andreas J

N1 - Funding Information: This work was supported by grants of the German Research Foundation (Deutsche Forschungsgemeinschaft) through the priority program SPP1710 ‘Dynamics of thiol-based redox switches in cellular physiology’ (ME1567/9-1/2, SCHW1719/ 7-1, HE1848/16-1), the Emmy Noether program (SCHW1719/ 1-1), an individual grant (ME1567/12-1), and through the Research Training Group 2064 “Water use efficiency and drought stress responses: From Arabidopsis to Barley,” I.K. was funded by the Doctoral Training Program of the Biotechnology and Biological Sciences Research Council (BBSRC); A.E.M. was funded by a PhD studentship from the John Innes Foundation; M. F. and J.B. are funded by BBSRC grant awards BB/P012523/1 and BB/P012574/1. A.M. is recipient of a Feodor Lynen Research Fellowship from the Alexander von Humboldt Foundation.

PY - 2021/7

Y1 - 2021/7

N2 - Iron-sulfur (Fe-S) clusters are ubiquitous cofactors in all life and are used in a wide array of diverse biological processes, including electron transfer chains and several metabolic pathways. Biosynthesis machineries for Fe-S clusters exist in plastids, the cytosol and mitochondria. A single monothiol glutaredoxin (GRX) is involved in Fe-S cluster assembly in mitochondria of yeast and mammals. In plants, the role of the mitochondrial homologue GRXS15 has only partially been characterized. Arabidopsis (Arabidopsis thaliana) grxs15 null mutants are not viable, but mutants complemented with the variant GRXS15 K83A develop with a dwarf phenotype similar to the knockdown line GRXS15amiR. In an in-depth metabolic analysis of the variant and knockdown GRXS15 lines, we show that most Fe-S cluster-dependent processes are not affected, including biotin biosynthesis, molybdenum cofactor biosynthesis, the electron transport chain and aconitase in the TCA cycle. Instead, we observed an increase in most TCA cycle intermediates and amino acids, especially pyruvate, glycine and branched-chain amino acids (BCAAs). Additionally, we found an accumulation of branched-chain α-keto acids (BCKAs), the first degradation products resulting from transamination of BCAAs. In wild-type plants, pyruvate, glycine and BCKAs are all metabolized through decarboxylation by mitochondrial lipoyl cofactor-dependent dehydrogenase complexes. These enzyme complexes are very abundant, comprising a major sink for lipoyl cofactor. Because biosynthesis of lipoyl cofactor depends on continuous Fe-S cluster supply to lipoyl synthase, this could explain why lipoyl cofactor-dependent processes are most sensitive to restricted Fe-S supply in grxs15 mutants.

AB - Iron-sulfur (Fe-S) clusters are ubiquitous cofactors in all life and are used in a wide array of diverse biological processes, including electron transfer chains and several metabolic pathways. Biosynthesis machineries for Fe-S clusters exist in plastids, the cytosol and mitochondria. A single monothiol glutaredoxin (GRX) is involved in Fe-S cluster assembly in mitochondria of yeast and mammals. In plants, the role of the mitochondrial homologue GRXS15 has only partially been characterized. Arabidopsis (Arabidopsis thaliana) grxs15 null mutants are not viable, but mutants complemented with the variant GRXS15 K83A develop with a dwarf phenotype similar to the knockdown line GRXS15amiR. In an in-depth metabolic analysis of the variant and knockdown GRXS15 lines, we show that most Fe-S cluster-dependent processes are not affected, including biotin biosynthesis, molybdenum cofactor biosynthesis, the electron transport chain and aconitase in the TCA cycle. Instead, we observed an increase in most TCA cycle intermediates and amino acids, especially pyruvate, glycine and branched-chain amino acids (BCAAs). Additionally, we found an accumulation of branched-chain α-keto acids (BCKAs), the first degradation products resulting from transamination of BCAAs. In wild-type plants, pyruvate, glycine and BCKAs are all metabolized through decarboxylation by mitochondrial lipoyl cofactor-dependent dehydrogenase complexes. These enzyme complexes are very abundant, comprising a major sink for lipoyl cofactor. Because biosynthesis of lipoyl cofactor depends on continuous Fe-S cluster supply to lipoyl synthase, this could explain why lipoyl cofactor-dependent processes are most sensitive to restricted Fe-S supply in grxs15 mutants.

UR - http://www.scopus.com/inward/record.url?scp=85111074869&partnerID=8YFLogxK

U2 - 10.1093/plphys/kiab172

DO - 10.1093/plphys/kiab172

M3 - Article

C2 - 33856472

VL - 186

SP - 1507

EP - 1525

JO - Plant physiology

JF - Plant physiology

SN - 0032-0889

IS - 3

ER -