A Phylogenomic Inventory of Meiotic Genes

Department of Biology, Roanoke College, Salem, VA 24153, USA.
Current Biology (Impact Factor: 9.57). 02/2005; 15(2):185-91. DOI: 10.1016/j.cub.2005.01.003
Source: PubMed


Sexual reproduction in eukaryotes is accomplished by meiosis, a complex and specialized process of cell division that results in haploid cells (e.g., gametes). The stereotypical reductive division in meiosis is a major evolutionary innovation in eukaryotic cells, and delineating its history is key to understanding the evolution of sex. Meiosis arose early in eukaryotic evolution, but when and how meiosis arose and whether all eukaryotes have meiosis remain open questions. The known phylogenetic distribution of meiosis comprises plants, animals, fungi, and numerous protists. Diplomonads including Giardia intestinalis (syn. G. lamblia) are not known to have a sexual cycle; these protists may be an early-diverging lineage and could represent a premeiotic stage in eukaryotic evolution. We surveyed the ongoing G. intestinalis genome project data and have identified, verified, and analyzed a core set of putative meiotic genes-including five meiosis-specific genes-that are widely present among sexual eukaryotes. The presence of these genes indicates that: (1) Giardia is capable of meiosis and, thus, sexual reproduction, (2) the evolution of meiosis occurred early in eukaryotic evolution, and (3) the conserved meiotic machinery comprises a large set of genes that encode a variety of component proteins, including those involved in meiotic recombination.

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    • "This is the major pathway used by lower eukaryotes, including protozoan parasites, to repair double stranded DNA damages (Bhattacharyya et al., 2004). Putative meiosis genes were detected in the genome of G. intestinalis (Ramesh et al., 2005) but much remains to be studied about the mechanism of homologous recombination in this parasite. Further studies of the proteins listed in Table S5 might reveal how Giardia deals with DNA damage. "
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    Experimental Parasitology 03/2015; 154. DOI:10.1016/j.exppara.2015.03.024 · 1.64 Impact Factor
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    • "The drying step is avoided in the drop-cryo procedure for SEM preparations, which enables a better 3D preservation of the chromosomes and a visualization of sister chromatids lying closely together is therefore difficult (Wanner and Schroeder-Reiter 2008). The protein inventory for sister chromatid cohesion in Giardia is strikingly reduced; we and others failed to identify a homolog of the Rad21/Scc1, which, together with the SMC1 and SMC3 heterodimer, is essential for the formation of the tripartite cohesin ring (Eme et al. 2011; Malik et al. 2008; Ramesh et al. 2005). Although sister chromatids in Giardia chromosomes are held together until anaphase, the cohesion and splitting mechanisms remain unclear . "
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    • "The best-characterized mechanism of ploidy change is sexual reproduction, which is thought to have evolved once very early in the eukaryotic lineage. Thus, factors regulating meiosis and recombination are conserved from fungi to man (Keeney 2001; Ramesh et al. 2005; Schurko and Logsdon 2008). Our understanding of sex has been greatly bolstered by studies in unicellular model yeasts such as S. cerevisiae and S. pombe. "
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