Sex Is a Ubiquitous, Ancient, and Inherent Attribute of Eukaryotic Life
PAPER Sex is a ubiquitous, ancient, and inherent attribute of COLLOQUIUM eukaryotic life Dave Speijera,1, Julius Lukešb,c, and Marek Eliášd,1 aDepartment of Medical Biochemistry, Academic Medical Center, University of Amsterdam, 1105 AZ, Amsterdam, The Netherlands; bInstitute of Parasitology, Biology Centre, Czech Academy of Sciences, and Faculty of Sciences, University of South Bohemia, 370 05 Ceské Budejovice, Czech Republic; cCanadian Institute for Advanced Research, Toronto, ON, Canada M5G 1Z8; and dDepartment of Biology and Ecology, University of Ostrava, 710 00 Ostrava, Czech Republic Edited by John C. Avise, University of California, Irvine, CA, and approved April 8, 2015 (received for review February 14, 2015) Sexual reproduction and clonality in eukaryotes are mostly Sex in Eukaryotic Microorganisms: More Voyeurs Needed seen as exclusive, the latter being rather exceptional. This view Whereas absence of sex is considered as something scandalous for might be biased by focusing almost exclusively on metazoans. a zoologist, scientists studying protists, which represent the ma- We analyze and discuss reproduction in the context of extant jority of extant eukaryotic diversity (2), are much more ready to eukaryotic diversity, paying special attention to protists. We accept that a particular eukaryotic group has not shown any evi- present results of phylogenetically extended searches for ho- dence of sexual processes. Although sex is very well documented mologs of two proteins functioning in cell and nuclear fusion, in many protist groups, and members of some taxa, such as ciliates respectively (HAP2 and GEX1), providing indirect evidence for (Alveolata), diatoms (Stramenopiles), or green algae (Chlor- these processes in several eukaryotic lineages where sex has oplastida), even serve as models to study various aspects of sex- – not been observed yet.
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