D-Lactate Dehydrogenase Links Methylglyoxal Degradation and Electron Transport through Cytochrome c

authored by

Elina Welchen, Jessica Schmitz, Philippe Fuchs, Lucila García, Stephan Wagner, Judith Wienstroer, Peter Schertl, Hans Peter Braun, Markus Schwarzländer, Daniel H. Gonzalez, Veronica G. Maurino

Abstract

Glycolysis generates methylglyoxal (MGO) as an unavoidable, cytotoxic by-product in plant cells. MGO scavenging is performed by the glyoxalase system, which produces D-lactate as an end product. D-Lactate dehydrogenase (D-LDH) is encoded by a single gene in Arabidopsis (Arabidopsis thaliana; At5g06580). It catalyzes in vitro the oxidation of D-lactate to pyruvate using flavin adenine dinucleotide as a cofactor; knowledge of its function in the context of the plant cell remains sketchy. Blue native-polyacrylamide gel electrophoresis of mitochondrial extracts combined with in gel activity assays using different substrates and tandem mass spectrometry allowed us to definitely show that D-LDH acts specifically on D-lactate, is active as a dimer, and does not associate with respiratory supercomplexes of the inner mitochondrial membrane. The combined use of cytochrome c (CYTc) loss-of-function mutants and respiratory complex III inhibitors showed that CYTc acts as the in vivo electron acceptor of D-LDH. CYTc loss-of-function mutants, as well as the D-LDH mutants, were more sensitive to D-lactate and MGO, indicating that they function in the same pathway. In addition, overexpression of D-LDH and CYTc increased tolerance to D-lactate and MGO. Together with fine-localization of D-LDH, the functional interaction with CYTc in vivo strongly suggests that D-lactate oxidation takes place in the mitochondrial intermembrane space, delivering electrons to the respiratory chain through CYTc. These results provide a comprehensive picture of the organization and function of D-LDH in the plant cell and exemplify how the plant mitochondrial respiratory chain can act as a multifunctional electron sink for reductant from cytosolic pathways.

Organisation(s)

Institute of Plant Genetics

External Organisation(s)

Universidad Nacional del Litoral
University of Bonn
University Hospital Düsseldorf

Type

Article

Journal

Plant physiology

Volume

172

Pages

901-912

No. of pages

12

ISSN

0032-0889

Publication date

10.2016

Publication status

Published

Peer reviewed

Yes

ASJC Scopus subject areas

Physiology, Genetics, Plant Science

Electronic version(s)

https://doi.org/10.1104/pp.16.01174 (Access: Open)