Rapid diversification of mating systems in ciliates

Abstract

Ciliates are a diverse group of microbial eukaryotes that exhibit tremendous variety in several aspects of their mating systems. To understand the evolutionary forces driving mating system diversification in ciliates, we use a comparative approach synthesizing data from many ciliate species in light of recent phylogenetic analyses. Specifically, we investigate the evolution of number of mating types, mode of mating type inheritance, and the molecular determinants of mating types across the taxonomic diversity of ciliates, with an emphasis on three well-studied genera: Tetrahymena, Paramecium, and Euplotes. We find that there have been many transitions in the number of mating types, and that the requirement of nuclear reorganization may be a more important factor than genetic exchange in determining the optimum number of mating types in a species. We also find that the molecular determinants of mating types and mode of inheritance are evolving under different constraints in different lineages of ciliates. Our results emphasize the need for further detailed examination of mating systems in understudied ciliate lineages.

The Evolution of Sex: a Perspective from the Fungal Kingdom

“…Outside the fungal kingdom, there have been multiple transitions from anisogamy to isogamy in ciliates, a diverse class of eukaryotic microbes. In ciliates, most genetic exchange involves the exchange of equally sized gametes, but at least two transitions to anisogamy in which the gametes are of unequal sizes and play different roles in the process of genetic exchange have occurred (58,200,235,275).…”

Origins of Eukaryotic Sexual Reproduction

“…haploid reductions via meiosis. That the LECA was sexual is no longer a matter of speculation/ debate as evidence of sex, and of genes exclusively involved in meiosis, has been found in all of the major eukaryotic radiations (Brawley and Johnson 1992;Ramesh et al 2005;Kobiyama et al 2007;Malik et al 2008;Phadke and Zufall 2009;Fritz-Laylin et al 2010;Lahr et al 2011;Peacock et al 2011;Vanstechelman et al 2013).…”

Epigenetic factors in vital functions of the ciliate Dileptus anser

“…As a result, a large amount of data on the physiology, biochemistry and molecular biology of sexual processes and mating types in ciliates has been accumulated (see reviews : Tsukii, 1988;Miyake, 1996). MT systems in these organisms, their genetic control and mode of inheritance appeared to be quite diverse (Phadke and Zufall, 2009). There are systems where MTs are directly and unambiguously determined by genes and their alleles.…”