Claudio Slamovits

The number of cases of lateral or horizontal gene transfer in eukaryotic genomes is growing steadily, but in most cases, neither the donor nor the recipient is known, and the biological implications of the transfer are not clear. We describe a relatively well-defined case of transfer from a cyanobacterial source to an ancestor of dinoflagellates that diverged before Oxyrrhis but after Perkinsus. This case is also exceptional in that 2 adjacent genes, a paralogue of the shikimate biosynthetic…

The general secretory (Sec) pathway is the main mechanism for protein secretion and insertion into endoplasmic reticulum and plasma membrane in prokaryotes and eukaryotes. However, the complete genome of the highly specialized microsporidian parasite Encephalitozoon cuniculi appears to lack a gene for Sec61beta, one of three universally conserved proteins that form the core of the Sec translocon. We have identified a putative, highly divergent homologue of Sec61beta in the genome of another…

CONCLUSION: The Streblomastix data show that the genome of the ancestor of excavates likely contained many introns and the subsequent evolution of introns has proceeded very differently in different excavate lineages: in Streblomastix there has been much stasis while in Trichomonas and Giardia most introns have been lost.

In pyrophosphate-dependent glycolysis, the ATP/ADP-dependent enzymes phosphofructokinase (PFK) and pyruvate kinase are replaced by the pyrophosphate-dependent PFK and pyruvate phosphate dikinase (PPDK), respectively. This variant of glycolysis is widespread among bacteria, but it also occurs in a few parasitic anaerobic eukaryotes such as Giardia and Entamoeba spp. We sequenced two genes for PPDK from the amitochondriate oxymonad Streblomastix strix and found evidence for PPDK in Trichomonas…

Eukaryotic nuclear genomes are generally considered to be large and gene-sparse, but extreme reduction has taken place several times, resulting in small genomes with a high gene-density. This process involves losing genes, compacting those that remain, or often both. Recently sequenced nuclear genomes include several that have converged to similar gene-densities by many means: variation in numbers and lengths of genes, intergenic regions and introns all contribute, but not equally in any given…

The gene density of eukaryotic nuclear genomes is generally low relative to prokaryotes, but several eukaryotic lineages (many parasites or endosymbionts) have independently evolved highly compacted, gene-dense genomes. The best studied of these are the microsporidia, highly adapted fungal parasites, and the nucleomorphs, relict nuclei of endosymbiotic algae found in cryptomonads and chlorarachniophytes. These systems are now models for the effects of compaction on the form and dynamics of the…

Microsporidia have been known for some time to possess among the smallest genomes of any eukaryote. There is now a completely sequenced microsporidian genome, as well as several other large-scale sequencing efforts, so the nature of these genomes is becoming apparent. This paper reviews some of the characteristics of microsporidian genomes in general, and some of the recent discoveries made through comparative genomic analyses. In general, microsporidian genomes are both reduced and compacted….

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Photoreactivation is the repair of DNA damage induced by ultraviolet light radiation using the energy contained in visible-light photons. The process is carried out by a single enzyme, photolyase, which is part of a large and ancient photolyase/cryptochrome gene family. We have characterised a photolyase gene from the microsporidian parasite, Antonospora locustae (formerly Nosema locustae) and show that it encodes a functional photoreactivating enzyme and is expressed in the infectious spore…

Microsporidian genomes are extraordinary among eukaryotes for their extreme reduction: although they are similar in form to other eukaryotic genomes, they are typically smaller than many prokaryotic genomes. At the same time, their rates of sequence evolution are among the highest for eukaryotic organisms. To explore the effects of compaction on nuclear genome evolution, we sequenced 685,000 bp of the Antonospora locustae genome (formerly Nosema locustae) and compared its organization with the…