Chapter 14 : Evolution of in the Species Complex: Sex, Ploidy, and Complete Sexual Cycles in , and

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Evolution of in the Species Complex: Sex, Ploidy, and Complete Sexual Cycles in , and , Page 1 of 2

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The best-studied species to date are the human pathogens and . However, neither of these species is as yet known to possess a complete meiotic sexual cycle. , , and are three members of this genus that are exciting prospects for further study. Of the three species discussed in this chapter, the sexual life cycle has been the best studied for this species. Multiple types of media are capable of inducing mating including dilute potato dextrose agar, 1% malt extract media, sodium acetate, yeast carbon base, V8, and SLAD. The anamorph has been cultured from a variety of ecological niches, including human clinical specimens, insects, fruit, and decaying matter. The sexual cycle of was first identified in 1952 by Wickerham and Burton, after recognizing that some yeasts previously classified to non-ascosporeforming genera actually represented the anamorphic form of a sexual species. That sexual species exist forms the basis of the argument that loss or restriction of sexual reproduction is the evolved state, possibly due to the energy expenditure required to undergo meiosis or to limit genetic exchange in a pathogen highly evolved to its host niche. Thus, continued study of the species complex will provide insight on interesting evolutionary questions regarding the evolution of signal transduction pathways, sexual reproduction, commensalism, and pathogenesis.

Citation: Reedy J, Heitman J. 2007. Evolution of in the Species Complex: Sex, Ploidy, and Complete Sexual Cycles in , and , p 235-245. In Heitman J, Kronstad J, Taylor J, Casselton L (ed), Sex in Fungi. ASM Press, Washington, DC. doi: 10.1128/9781555815837.ch14

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Candida albicans
Candida lusitaniae
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Figure 14.1

Phylogeny of anamorphic and teleomorphic species. Species are designated by the teleomorph or anamorph designation or both. An asterisk indicates the proposed point of CUG codon capture and the expansion of the locus to include , and genes. Species with gray shading are those that encode CTG as serine rather than leucine. Black dots indicate teleomorphic species with a anamorph. Node numbers are indicated above each branch. Phylogeny is adapted from Diezmann et al. (11).

Citation: Reedy J, Heitman J. 2007. Evolution of in the Species Complex: Sex, Ploidy, and Complete Sexual Cycles in , and , p 235-245. In Heitman J, Kronstad J, Taylor J, Casselton L (ed), Sex in Fungi. ASM Press, Washington, DC. doi: 10.1128/9781555815837.ch14
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Image of Figure 14.2
Figure 14.2

Life cycle of . (A) Diagrammatic representation of the life cycle. (B) Differential interference contrast images of each stage of the life cycle. Cells of opposite mating types were incubated on dilute potato dextrose agar media, stained with DAPI (4′,6′-diamidino-2-phenylindole), and photographed at 24 to 72 h after coincubation. Scale bar is 5µm. Haploid yeast cells of opposite mating types undergo conjugation. Following conjugation one parental nuclei traverses the conjugation tube to enter the cell of the mating partner. Asci formed contain 1 to 2 clavate ascospores per ascus.

Citation: Reedy J, Heitman J. 2007. Evolution of in the Species Complex: Sex, Ploidy, and Complete Sexual Cycles in , and , p 235-245. In Heitman J, Kronstad J, Taylor J, Casselton L (ed), Sex in Fungi. ASM Press, Washington, DC. doi: 10.1128/9781555815837.ch14
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Figure 14.3

Mating-type-like loci of species. (A) Depiction of the α loci of and . (B) loci of , , and . The genes contained within the loci are represented by black arrows. The genes flanking the loci are depicted in white. The absence of a gene in a particular locus is denoted by an X.

Citation: Reedy J, Heitman J. 2007. Evolution of in the Species Complex: Sex, Ploidy, and Complete Sexual Cycles in , and , p 235-245. In Heitman J, Kronstad J, Taylor J, Casselton L (ed), Sex in Fungi. ASM Press, Washington, DC. doi: 10.1128/9781555815837.ch14
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Generic image for table
Table 14.1

species with known teleomorphs

Citation: Reedy J, Heitman J. 2007. Evolution of in the Species Complex: Sex, Ploidy, and Complete Sexual Cycles in , and , p 235-245. In Heitman J, Kronstad J, Taylor J, Casselton L (ed), Sex in Fungi. ASM Press, Washington, DC. doi: 10.1128/9781555815837.ch14

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