Microbial predators form a new supergroup of eukaryotes

ENOD93 interacts with cytochrome c oxidase altering respiratory ATP production and root growth in plants

“…In the latter case, homologs generally had an N-terminal region similar to ENOD93 and an additional C-terminal portion containing a conserved "Hig_1_N" domain thought to be involved in the cellular response to hypoxia. The opposite orientation of regions similar to ENOD93 and Hig_1_N was noted in provorans (Tikhonenkov et al, 2022) and bolidophytes.…”

The ancestral shape of the access proton path of mitochondrial ATP synthases revealed by a split subunit-a

“…For individual lineages mapped on the phylogenetic tree based on Burki, et al 2020 and Tikhonenkov, et al 2022 following features are shown: number of species included in the analyses (in parentheses); genome, in which subunit-a/a N is encoded (“mt” – mitochondrial, “n” – nuclear); presence or absence of helices h N and h 1 of subunit-a/a N ; selected representative species used in the analyses presented in the following columns (for species shown in bold a cryoEM structure of ATP synthase has been reported); sequence of h N and flanking residues (universally conserved phenylalanine is shown in red, other conserved residues of the SPLEQF motif, or the FXXF motif in Metazoa, are shown in bold); average hydrophobicity of the entire subunit-a (FL), region h 1 -h 6 , and region h 5 -h 6 (blue – more hydrophobic, red – less hydrophobic); presence or absence of the histidine residue shown to coordinate a water molecule in the Grotthuss chain in trypanosomal (His155) and bovine (His168) ATP synthase (column H), and of the acidic residue (aspartate or glutamate) involved in proton translocation (Asp202 in T. brucei ; column D/E).…”

How mitochondria showcase evolutionary mechanisms and the importance of oxygen

“…This last protein seems to have been replaced by a “viral‐type” nucleus encoded polymerase in all other known eukaryotes, which might help explain the larger amount of overall gene retention in this lineage. The newly discovered supergroup of unicellular eukaryotic predators, the “Provora” (separated into two ancient subgroups) are also illuminating here 70 . (i) Though ancient, and globally present, they have only very recently been discovered, because of their numerical rarity, a trait shared with top predators among metazoans; (ii) Though less proteins (> 50) are encoded by their mitochondria than is the case for Jakobids, they still contain more than double the amount found in metazoans, which might imply these organisms represent the most ancient predators, while metazoans and the related fungi started out as more passive consumers of organic matter, allowing more extensive transfer early on; (iii) The Provora mitochondrial diversity easily surpasses that of the metazoans, attesting to antiquity of the lineage and several population bottlenecks, with, for example, one of the subgroups still holding on to three complex II subunits, while the other one starts to resemble the metazoan configuration with migration of all three to the nucleus; (iv) As such, these organisms showcase the opposing effects of the importance of continuous efficient ATP production (hampering gene transfer) and small population sizes (allowing founder effects of further gene transfer).…”

“…The newly discovered supergroup of unicellular eukaryotic predators, the "Provora" (separated into two ancient subgroups) are also illuminating here. 70 (i) Though ancient, and globally present, they have only very recently been discovered, because of their numerical rarity, a trait shared with top predators among metazoans; (ii) Though less proteins (> 50) are encoded by their mitochondria than is the case for Jakobids, they still contain more than double the amount found in metazoans, which might imply these organisms represent the most ancient predators, while metazoans and the related fungi started out as more passive consumers of organic matter, allowing more extensive transfer early on;…”

“…It is not my intention to give an extensive overview of mitochondrial phenotypes (or the huge diversity in morphology 68 ) to be found in all of eukaryotic diversity, ranging from: those that still retain most of the likeness to their proteobacterial forebear, found in jakobids, 69 those present in a newly described class of unicellular predators, 70 the streamlined efficient mitochondria of some animals, such as ourselves; see, for example, 71 mitochondrion-related organelles (MROs), such as hydrogenosomes, using alternative terminal acceptors instead of O 2 , 72,73 and mitosomes, which have not retained any role in ATP generation, 74 to examples of eukaryotes that have lost mitochondria all together. 75 Though not everybody agrees, most researchers think this reflects an overall decline from a fully integrated oxidative mitochondrion, as present in LECA.…”