The Birds and the Bees and the Flowers and the Trees: Lessons from Genetic Mapping of Sex Determination in Plants and Animals

Abstract

The ability to identify genetic markers in nonmodel systems has allowed geneticists to construct linkage maps for a diversity of species, and the sex-determining locus is often among the first to be mapped. Sex determination is an important area of study in developmental and evolutionary biology, as well as ecology. Its importance for organisms might suggest that sex determination is highly conserved. However, genetic studies have shown that sex determination mechanisms, and the genes involved, are surprisingly labile. We review studies using genetic mapping and phylogenetic inferences, which can help reveal evolutionary pattern within this lability and potentially identify the changes that have occurred among different sex determination systems. We define some of the terminology, particularly where confusion arises in writing about such a diverse range of organisms, and highlight some major differences between plants and animals, and some important similarities. We stress the importance of studying taxa suitable for testing hypotheses, and the need for phylogenetic studies directed to taxa where the patterns of changes can be most reliably inferred, if the ultimate goal of testing hypotheses regarding the selective forces that have led to changes in such an essential trait is to become feasible.

Origins of Eukaryotic Sexual Reproduction

“…In modern multicellular organisms, the MTD systems are themselves complex (Pomiankowski et al 2004;Kimchi et al 2007;Salz 2011), highly diverse (Haag and Doty 2005), and often labile (Charlesworth and Mank 2010), and the H1/H2 programs they specify have expanded to include control over tissue and organ differentiation and, in animals, brain and behavioral patterning.…”

The sex-specific region of sex chromosomes in animals and plants

“…The most dramatic example of the expansion phase is the 570-Mb Y chromosome compared to the 420-Mb X chromosome in Silene latifolia (Liu et al 2004). The degree of SDR expansion is generally positively correlated to the time of suppression of the SDR and sex chromosome divergence within a particular lineage of organisms in the early stages of sex chromosome evolution, though ratite birds, with evolutionarily old ZW chromosomes, have a relatively small SDR (Tsuda et al 2007;Charlesworth and Mank 2010). The papaya sex chromosomes evolved about 2-3 Ma ago (Mya) (Yu et al 2008), whereas the sex chromosomes of S. latifolia evolved about 10 Mya (Bergero et al 2007).…”

Sex determination in dioecious Mercurialis annua and its close diploid and polyploid relatives

“…; and s.d. with both genetic and environmental components (Bull, 1983;Werren and Beukeboom, 1998;Uller et al, 2007;Charlesworth and Mank, 2010;Janousek and Mrackova, 2010;Beukeboom and Perrin, 2014). Remarkably, quite different s.d.…”