Direct evidence for secondary loss of mitochondria in Entamoeba histolytica.

Abstract

Archezoan protists are thought to represent lineages that diverged from other eukaryotes before acquisition of the mitochondrion and other organelles. The parasite Entamoeba histolytica was originally included in this group. Ribosomal RNA based phylogenies, however, place E. histolytica on a comparatively recent branch of the eukaryotic tree, implying that its ancestors had these structures. In this study, direct evidence for secondary loss of mitochondrial function was obtained by isolating two E. histolytica genes encoding proteins that in other eukaryotes are localized in the mitochondrion: the enzyme pyridine nucleotide transhydrogenase and the chaperonin cpn60. Phylogenetic analysis of the E. histolytica homolog of cpn60 confirmed that it is specifically related to the mitochondrial lineage. The data suggest that a mitochondrial relic may persist in this organism. Similar studies are needed in archezoan protists to ascertain which, if any, eukaryotic lineages primitively lack mitochondria.

Multiple secondary origins of the anaerobic lifestyle in eukaryotes

“…For example, among plants there are examples where particular genes appear on the mitochondrial genome in some lineages, but in other lineages they are encoded by the host nuclear genome (Adams & Palmer 2003). Despite the need to invoke such gene transfer, the hypothesis that the genes in table 1 came from the mitochondrial endosymbiont is probably now the standard interpretation of these data (Boorstein et al 1994;Viale & Arakaki 1994;Clark & Roger 1995).…”

Mitosomes of Entamoeba histolytica are abundant mitochondrion-related remnant organelles that lack a detectable organellar genome

“…Some, such as those of Entamoeba and Cryptosporidium, have been shown to contain chaperonin Cpn60, a protein known to participate in the refolding of imported proteins (Sigler et al, 1998; Mai et al, 1999;Tovar et al, 1999;Riordan et al, 2003); mitosomes of Trachipleistophora contain a mitochondrialtype Hsp70 (mtHsp70), a molecular motor that helps internalize proteins into the organelle (Matouschek et al, 2000;Williams et al, 2002). Other proteins have also been suggested as putative mitosomal components in various amitochondrial lineages but their cellular localization has not been demonstrated experimentally (Clark & Roger, 1995;Bakatselou et al, 2000Bakatselou et al, , 2003Katinka et al, 2001;Morrison et al, 2001;Zhu & Keithly, 2002;Arisue et al, 2002). Perhaps the most significant finding in relation to the biology of mitosomes is the direct demonstration that Giardia mitosomes function in the biosynthesis of molecular iron-sulphur (Fe-S) clusters and in their subsequent incorporation into functional Fe-S proteins (Tovar et al, 2003).…”

FRIENDLY Regulates Mitochondrial Distribution, Fusion, and Quality Control in Arabidopsis

“…Mitochondria are a defining component of eukaryotes: even the few groups of amitochondriate protists are believed to have secondarily lost the organelle (Clark and Roger, 1995;Bui et al, 1996;Gray et al, 1999). The long shared history of eukaryotes has led to considerable conservation of mitochondrial structure and function, although some divergence of both has occurred between plants, fungi, and animals since they split from their most recent common ancestor approximately 1,500 million years ago (Feng et al, 1997;Douzery et al, 2004;Hedges et al, 2004).…”