bims-cytox1 2024-09-01 papers

Issue of 2024‒09‒01
two papers selected by
Gavin McStay, Liverpool John Moores University

Plant Cell. 2024 Aug 23. pii: koae242. [Epub ahead of print]

EARLY NODULIN93 acts via cytochrome c oxidase to alter respiratory ATP production and root growth in plants.

Chun Pong Lee, Xuyen H Le, Ryan M R Gawryluk, José A Casaretto, Steven J Rothstein, A Harvey Millar.

EARLY NODULIN 93 (ENOD93) has been genetically associated with biological nitrogen fixation in legumes and nitrogen use efficiency in cereals, but its precise function is unknown. We show that hidden Markov models define ENOD93 as a homolog of the N-terminal domain of RESPIRATORY SUPERCOMPLEX FACTOR 2 (RCF2). RCF2 regulates cytochrome oxidase (CIV), influencing the generation of a mitochondrial proton motive force in yeast (Saccharomyces cerevisiae). Knockout of ENOD93 in Arabidopsis (Arabidopsis thaliana) causes a short root phenotype and early flowering. ENOD93 is associated with a protein complex the size of CIV in mitochondria, but neither CIV abundance nor its activity changed in ruptured organelles of enod93. However, a progressive loss of ADP-dependent respiration rate was observed in intact enod93 mitochondria, which could be recovered in complemented lines. Mitochondrial membrane potential was higher in enod93 in a CIV-dependent manner, but ATP synthesis and ADP depletion rates progressively decreased. The respiration rate of whole enod93 seedlings was elevated, and root ADP content was nearly double that in wild type without a change in ATP content. We propose that ENOD93 and HYPOXIA-INDUCED GENE DOMAIN 2 (HIGD2) are the functional equivalent of yeast RCF2 but have remained undiscovered in many eukaryotic lineages because they are encoded by two distinct genes.

Keywords: ATP synthesis; Complex IV; Early nodulin 93; RCF2; mitochondrial oxidative phosphorylation

DOI: https://doi.org/10.1093/plcell/koae242

iScience. 2024 Aug 16. 27(8): 110560

Mitochondrial translation is the primary determinant of secondary mitochondrial complex I deficiencies.

Kristýna Čunátová, Marek Vrbacký, Guillermo Puertas-Frias, Lukáš Alán, Marie Vanišová, María José Saucedo-Rodríguez, Josef Houštěk, Erika Fernández-Vizarra, Jiří Neužil, Alena Pecinová, Petr Pecina, Tomáš Mráček.

Individual complexes of the mitochondrial oxidative phosphorylation system (OXPHOS) are not linked solely by their function; they also share dependencies at the maintenance/assembly level, where one complex depends on the presence of a different individual complex. Despite the relevance of this "interdependence" behavior for mitochondrial diseases, its true nature remains elusive. To understand the mechanism that can explain this phenomenon, we examined the consequences of the aberration of different OXPHOS complexes in human cells. We demonstrate here that the complete disruption of each of the OXPHOS complexes resulted in a decrease in the complex I (cI) level and that the major reason for this is linked to the downregulation of mitochondrial ribosomal proteins. We conclude that the secondary cI defect is due to mitochondrial protein synthesis attenuation, while the responsible signaling pathways could differ based on the origin of the OXPHOS defect.

Keywords: Biochemistry; Cell biology; Molecular biology

DOI: https://doi.org/10.1016/j.isci.2024.110560