Mechanistic plasticity of sexual reproduction and meiosis in the Candida pathogenic species complex.
BACKGROUND
Candida species are microbial pathogens originally thought to be asexual, but several are now recognized as sexual or parasexual. Candida albicans, the most common fungus infecting humans, is an obligate diploid with a parasexual cycle involving mating, recombination, and genome reduction but no recognized meiosis. Others (C. lusitaniae, C. guilliermondii) are haploid, and their mating produces spores, suggestive of complete meiotic sexual cycles. However, comparative genomic analysis reveals that these species lack key meiotic components, including the recombinase Dmc1 and cofactors (Mei5/Sae3), synaptonemal-complex proteins (Zip1-Zip4/Hop1), and the crossover interference pathway (Msh4/5).


RESULTS
Here we elucidate the structure and functions of the mating-type (MAT) locus and establish that C. lusitaniae undergoes meiosis during its sexual cycle. The MAT-encoded a2 (high-mobility group) and alpha1 (alpha domain) factors specify a and alpha cell identity, whereas the a1 homeodomain protein drives meiosis and sporulation and functions without its canonical heterodimeric partner, alpha2. Despite the apparent loss of meiotic genes, C. lusitaniae undergoes meiosis during sexual reproduction involving diploid intermediates, frequent SPO11-dependent recombination, and whole-genome reduction generating haploid progeny. The majority of meiotic progeny are euploid, but approximately one-third are diploid/aneuploid.


CONCLUSIONS
The cell identity and meiotic pathways have been substantially rewired, and meiotic generation of both recombinant and aneuploid progeny may expand genetic diversity. These findings inform our understanding of sexual reproduction in pathogenic microbes and the evolutionary plasticity of the meiotic machinery, with implications for the sexual nature of C. albicans and the generation and consequences of aneuploidy in biology and medicine.
Reedy
Jennifer L
JL
Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC 27710, USA.
Floyd
Anna M
AM
Heitman
Joseph
J
D000782:Aneuploidy; D002175:Candida / Q000166:cytology / Q000235:genetics / Q000502:physiology*; D004171:Diploidy; D004706:Endodeoxyribonucleases; D004950:Esterases / Q000502:physiology; D049770:Genes, Mating Type, Fungal; D016681:Genome, Fungal; D008540:Meiosis / Q000502:physiology*; D008969:Molecular Sequence Data; D011995:Recombination, Genetic; D012098:Reproduction / Q000235:genetics / Q000502:physiology; D013172:Spores, Fungal / Q000235:genetics; D014157:Transcription Factors / Q000502:physiology; D000099257:Meiotic Recombination Protein SPO11
D004706:Endodeoxyribonucleases; D004950:Esterases; D014157:Transcription Factors; D000099257:Meiotic Recombination Protein SPO11