Deletion of the ATP20 gene in Ustilago maydis produces an unstable dimer of F1FO-ATP synthase associated with a decrease in... 2022 Esparza-Perusquía

[Andy]

Full title: Deletion of the ATP20 gene in Ustilago maydis produces an unstable dimer of F1FO-ATP synthase associated with a decrease in mitochondrial ATP synthesis and a high H2O2 production

Highlights

• atp20 gene deletion did not modify the mitochondrial cristae architecture.
• atp20 gene deletion did not affect the presence of dimeric state of complex V.
• Dimer of complex V is instable in the atp20Δ strain.
• Instability of dimer of complex V is associated to mitochondrial ATP synthesis decrease.
• ROS production increase in the atp20Δ strain associated to AOX expression

Abstract

The F1FO-ATP synthase uses the energy stored in the electrochemical proton gradient to synthesize ATP. This complex is found in the inner mitochondrial membrane as a monomer and dimer. The dimer shows higher ATPase activity than the monomer and is essential for cristae folding. The monomer-monomer interface is constituted by subunits a, i/j, e, g, and k. The role of the subunit g in a strict respiratory organism is unknown.

A gene knockout was generated in Ustilago maydis to study the role of subunit g on mitochondrial metabolism and cristae architecture. Deletion of the ATP20 gene, encoding the g subunit, did not affect cell growth or glucose consumption, but biomass production was lower in the mutant strain (gΔ strain). Ultrastructure observations showed that mitochondrial size and cristae shape were similar in wild-type and gΔ strains. The mitochondrial membrane potential in both strains had a similar magnitude, but oxygen consumption was higher in the WT strain. ATP synthesis was 20 % lower in the gΔ strain. Additionally, the mutant strain expressed the alternative oxidase in the early stages of growth (exponential phase), probably as a response to ROS stress. Dimer from mutant strain was unstable to digitonin solubilization, avoiding its isolation and kinetic characterization. The isolated monomeric state activated by n-dodecyl-β-D-maltopyranoside showed similar kinetic constants to the monomer from the WT strain. A decrease in mitochondrial ATP synthesis and the presence of the AOX during the exponential growth phase suggests that deletion of the g gene induces ROS stress.

Paywall, https://www.sciencedirect.com/science/article/abs/pii/S0005272822004200

 

[Trish]

Ustilago magus is a fungus that grows on corn and is called corn smut, according to wikipedia. I have no idea whether mitochondria in fungi have the same genetic code as mitochondria in humans and therefore what relevance this might have.

 

[Peter T]

Ustilago magus is a fungus that grows on corn and is called corn smut, according to wikipedia. I have no idea whether mitochondria in fungi have the same genetic code as mitochondria in humans and therefore what relevance this might have.

Looking on line both human mitochondrial DNA and fungal DNA are thought to be of bacterial origin, but there are differences in animal, plant and fungal mitochondria:

Plant mitochondria share a functional role with their fungal and animal counterparts, and their genomes have a number of genes in common. In almost every other aspect, however, plant mitochondrial genomes differ. Whereas animal genomes are very small (14-18 kb) and fungal genomes somewhat larger (70-100 kb), known plant mitochondrial genomes range in size from 187 kb to over 2400 kb. Plant mitochondrial genomes have a variety of other distinctive or unique features. They often have multiple large repeated regions, some of which recombine frequently to yield a multipartite genome structure. Some subgenomes are present at extremely low (substoichiometric) levels, but can become amplified to become major constituents. Plant mitochondrial genes contain mainly group II introns, some of which are trans-spliced. The transcripts of many mitochondrial protein-coding genes undergo C-to-U RNA editing. Several mitochondrial tRNAs are known to be transcribed from nuclear genes and imported into the mitochondrion. While only a few mitochondrial genomes from plants have been completely sequenced to date, at least half of the DNA in each of these genomes is still of unknown origin. Comparisons between monocot and dicot mitochondrial genomes show that, in general, only genic exons are conserved. Even between rice and maize, or between Arabidopsis and rapeseed, most of the intergenic space is not conserved. On relatively short evolutionary time scales, plant mitochondrial genomes are in flux, taking up exogenous DNA, losing portions of their DNA and rearranging the order of their sequences

See https://link.springer.com/chapter/10.1007/978-1-4020-3166-3_6 .