%0 Journal Article
%T Meiosis genes in Daphnia pulex and the role of parthenogenesis in genome evolution
%A Andrew M Schurko
%A John M Logsdon
%A Brian D Eads
%J BMC Evolutionary Biology
%D 2009
%I BioMed Central
%R 10.1186/1471-2148-9-78
%X We report an inventory of 130 homologs representing over 40 genes encoding proteins with diverse roles in meiotic processes in the genome of D. pulex. Many genes involved in cell cycle regulation and sister chromatid cohesion are characterized by expansions in copy number. In contrast, most genes involved in DNA replication and homologous recombination are present as single copies. Notably, RECQ2 (which suppresses homologous recombination) is present in multiple copies while DMC1 is the only gene in our inventory that is absent in the Daphnia genome. Expression patterns for 44 gene copies were similar during meiosis versus parthenogenesis, although several genes displayed marked differences in expression level in germline and somatic tissues.We propose that expansions in meiotic gene families in D. pulex may be associated with parthenogenesis. Taking into account our findings, we provide a mechanistic model of parthenogenesis, highlighting steps that must differ from meiosis including sister chromatid cohesion and kinetochore attachment.Sexual reproduction (i.e. meiosis and syngamy) is the predominant reproductive mode in eukaryotes, yet parthenogenesis (i.e. asexual reproduction) is present in all major lineages. Among animals, cyclical parthenogenesis, which alternates bouts of clonal and sexual reproduction, is restricted to monogonont rotifers, digenean trematodes, and several arthropod lineages [1]. Obligate parthenogenesis is much more common but is predicted ultimately to drive lineages to extinction due to the accumulation of deleterious mutations or inability to adapt to environmental changes [2]. The origins of obligate parthenogens are often attributed to the loss of meiosis via interspecific hybridization [3,4] or irreversible changes in ploidy [5,6], yet other mechanisms must also exist. Among animals, thousands of parthenogenetic species have been described, and volumes have been written describing the cytogenetic manifestations of many different types
%U http://www.biomedcentral.com/1471-2148/9/78