Wong Simon, Fares Mario A, Zimmermann Wolfgang, Butler Geraldine, Wolfe Kenneth H
Department of Genetics, Smurfit Institute, University of Dublin, Trinity College, Dublin 2, Ireland.
Genome Biol. 2003;4(2):R10. doi: 10.1186/gb-2003-4-2-r10. Epub 2003 Jan 23.
Candida glabrata is a pathogenic yeast of increasing medical concern. It has been regarded as asexual since it was first described in 1917, yet phylogenetic analyses have revealed that it is more closely related to sexual yeasts than other Candida species. We show here that the C. glabrata genome contains many genes apparently involved in sexual reproduction.
By genome survey sequencing, we find that genes involved in mating and meiosis are as numerous in C. glabrata as in the sexual species Kluyveromyces delphensis, which is its closest known relative. C. glabrata has a putative mating-type (MAT) locus and a pheromone gene (MFALPHA2), as well as orthologs of at least 31 other Saccharomyces cerevisiae genes that have no known roles apart from mating or meiosis, including FUS3, IME1 and SMK1.
We infer that C. glabrata is likely to have an undiscovered sexual stage in its life cycle, similar to that recently proposed for C. albicans. The two Candida species represent two distantly related yeast lineages that have independently become both pathogenic and 'asexual'. Parallel evolution in the two lineages as they adopted mammalian hosts resulted in separate but analogous switches from overtly sexual to cryptically sexual life cycles, possibly in response to defense by the host immune system.
光滑念珠菌是一种在医学上日益受到关注的致病性酵母。自1917年首次被描述以来，它一直被视为无性繁殖，但系统发育分析表明，与其他念珠菌属相比，它与有性酵母的关系更为密切。我们在此表明，光滑念珠菌基因组包含许多明显参与有性生殖的基因。
通过基因组调查测序，我们发现参与交配和减数分裂的基因在光滑念珠菌中的数量与在其已知关系最近的有性物种德尔斐克鲁维酵母中的数量一样多。光滑念珠菌有一个假定的交配型（MAT）位点和一个信息素基因（MFALPHA2），以及至少31个酿酒酵母其他基因的直系同源基因，这些基因除了交配或减数分裂外没有已知功能，包括FUS3、IME1和SMK1。
我们推断光滑念珠菌在其生命周期中可能有一个未被发现的有性阶段，类似于最近为白色念珠菌所提出的阶段。这两种念珠菌代表了两个远缘相关的酵母谱系，它们独立地变得既具有致病性又“无性”。这两个谱系在采用哺乳动物宿主时的平行进化导致了从明显有性到隐性有性生命周期的独立但类似的转变，这可能是对宿主免疫系统防御的一种反应。
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