A SUF Fe-S Cluster Biogenesis System in the Mitochondrion-Related Organelles of the Anaerobic Protist Pygsuia

Abstract

The unique functional profile of this MRO underscores the tremendous plasticity of mitochondrial function within eukaryotes and showcases the role of LGT in forging metabolic mosaics of ancestral and newly acquired organellar pathways.

Diversity and origins of anaerobic metabolism in mitochondria and related organelles

“…To date, a detailed prediction of MRO metabolism has only been performed for Pygsuia biforma [79]. The Pygsuia genome encodes MRO-targeted proteins involved in protein import and folding, amino acid, fatty acid and lipid metabolism.…”

An ancestral bacterial division system is widespread in eukaryotic mitochondria

“…This overall pattern raises the question of why Min proteins were retained in some taxa, yet lost in others. No correlation was found with mitochondrial cristae morphology, because Min proteins were found in organisms possessing discoid (e.g., P. kirbyi) (56) or tubular (e.g., A. godoyi) (74) cristae, as well as in lineages with MROs that apparently lack cristae entirely (e.g., A. incarcerata and P. biforma) (68,69). Nor is there any obvious difference in either overall mitochondrial morphology or lifestyle between lineages that possess Min proteins and lineages that do not.…”

“…All complete genomes encoding at least one Min protein also encoded at least one FtsZ homolog; however, the reverse was not true. Min proteins were retained not only in lineages with typical aerobic mitochondria, but also in lineages possessing mitochondrion-related organelles (MROs) such as A. incarcerata (68) and P. biforma (69).…”

Symbiogenesis, gradualism, and mitochondrial energy in eukaryote origin

“…How can eukaryotes acquire genes from donors that lack the traits to be acquired? Third, the popularity of eukaryote LGT (69,70,71,72,140,144,145) should not obscure the fact that it is Lamarckian in tooth and claw. Eukaryote LGT proponents are saying that the genes required for survival in anaerobic environments (72), or the genes required for the origin of eukaryote complexity (141) are first acquired from outside the eukaryotic lineage, then inherited within eukaryotes to fulfill some purpose, for example adaptation to anaerobic environments or origins of complexity.…”

“…Two main ideas are currently discussed for the origin of eukaryotic anaerobes, one gradualist, one symbiogenic. The gradualist view is that eukaryotes started out their evolutionary history as obligate aerobes, that the ancestral mitochondrion was an obligate aerobe specialist like Rickettsia (68), and that the ability to survive in anaerobic environments was gradually acquired during evolution in various eukaryotic lineages via lateral gene transfer (LGT), either from prokaryotes or from eukaryotes that had themselves become anaerobic via earlier gradual LGTs (69,70,71,72,73). There are several major problems with the origin of eukaryotic anaerobes via LGT, as discussed at length elsewhere (74), in addition to minor problems, such as the fact that the gradualist LGT origin for eukaryote anaerobes hinges wholly upon Lamarckian inheritance (traits being impressed from the environment into eukaryotic inheritance).…”