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{ Category Archives } research articles

Exon shuffling and the origin of the mitochondrial targeting function in plant cytochrome cl precursor (Long et al., 1995)

An article that illustrates the widespread presence of introns in the eukaryotic genes coding for mitochondrial genes. As well, they show through the existence of conserved introns/exons that the targeting information for the mitochondria has been derived from another protein. This is in line with a gradual evolution of nuclear genes that were targeted to […]

Analysis of Ribosomal Protein Gene Structures: Implications for Intron Evolution (Yoshihama et al., 2006)

This article is about introns in the nuclear genes coding for mitochondrial proteins. The existence of these introns and these nuclear genes is in line with a nuclear origin of these genes, especially when the intron positions are conserved. The current article assumes (wrongly, imo) that the genes are of bacterial origin and proposes that the […]

An Algal Nucleus-encoded Subunit of Mitochondrial ATP Synthase Rescues a Defect in the Analogous Human Mitochondrial-encoded Subunit (Ojaimi et al., 2001)

Here, it is shown that essential mitochondrial genes can be nucleus-encoded (Chlamydomonas), in this case the subunit ATPase6. The gene shows eukaryotic characteristics including introns and targeting sequences. The algal gene is even functional in mammalian cells.
From the abstract: Unlike most organisms, the mitochondrial DNA (mtDNA) of Chlamydomonas reinhardtii, a green alga, does not encode […]

Regular Spliceosomal Introns Are Invasive in Chlamydomonas reinhardtii: 15 Introns in the Recently Relocated Mitochondrial cox2 and cox3 Genes (Watanabe and Ohama, 2001)

Here they analyze the cox3 and cox2 genes that are absent in the mitochondrial genome, but present in the nuclear genome where they contain spliceosomal introns like in many eukaryotic genes. Also, the genes contain mitochondrial target sequences. Thus, these genes could represent the ancient mitochondrial genome where cox2 and cox3 were later added.
From the […]

Mitochondrial Type Iron-Sulfur Cluster Assembly in the Amitochondriate Eukaryotes Trichomonas vaginalis and Giardia intestinalis, as Indicated by the Phylogeny of IscS (Tachezy et al., 2001)

This article shows a common origin between mitochondria and the amitochondriate organisms that contain either a mitosome or a hydrogenosomes. All organisms use FeS clusters and they show that the proteins involved are similar. This article places it in the context of a loss of function in the mitosomes, while I think it just indicates […]

Giardia mitosomes and trichomonad hydrogenosomes share a common mode of protein targeting (Dolezal et al., 2005)

This article shows that mitosomes and hydrogenosomes have targeting mechanisms that are similar. This is expected when mitochondria and related organelles were both derived from the endomembrane system and where the anaerobic organelles preceded the mitochondria in evolution.
Abstract: […] by the discovery of mitochondria-like double membrane-bound organelles called mitosomes. Here, we report that proteins targeted […]

Microsporidian mitosomes retain elements of the general mitochondrial targeting system (Burri et al., 2006)

This article regards the microsporidia as highly derived organisms and all their claims have to be seen in this context. Still, this article provides interesting data how a precursor mitochondrion, in this case the mitosome could have looked like. They find simpler import mechanisms based on a a few subunits of the mitochondrial ones and find that […]

Cryptosporidium parvum Mitochondrial-Type HSP70 Targets Homologous and Heterologous Mitochondria (Slapeta and Keithly, 2004)

In this article they describe a HSP70 gene that they call mitochondrial, but all they really can say is that it has an homology with a mitochondrial gene. Since they assume that this gene has been derived from an endosymbiont, this biases the entire article, but still they have some interesting results. They show that […]

Electron Tomographic and Ultrastructural Analysis of the Cryptosporidium parvum Relict Mitochondrion, its Associated Membranes, and Organelles (Keithly et al., 2005)

This abstract shows that the Cryptosporidium mitochondrion is associated with the endoplasmic reticulum, and could be relevant for the origin of mitochondria if it represents an intermediate. An endomembrane-derived mitochondrion could be expected to associate with the ER. Here we can see the as well my proposed scenario for the origin of the nucleus and […]

Complete Genome Sequence of the Apicomplexan, Cryptosporidium parvum (Abrahamsen et al., 2004)

This article describes the genome sequence of Cryptosporidium which lacks a mitochondrial genome and is thus completely dependent on the eukaryotic nucleus. Their conclusion is that it has lost its genome and its mitochondrion is degenerate, which is again a pity since it becomes difficult to see what their real data is and what they […]