In the April 21, 2005, issue of Nature, the researchers reported that, in the infectious fungus Cryptococcus neoformans, members of the same "sex" can mate and produce offspring. Infection with the fungus can prove life-threatening in humans, and the findings might improve understanding of the fungal biology that underlies the infectious process, the researchers said. Discovery of the same-sex mating might also help elucidate basic principles governing the evolution of sex, they said.
"Sex is generally beneficial as a means to produce offspring with different gene combinations that can adapt more rapidly to new environments," said HHMI investigator Joseph Heitman, M.D., Ph.D., of Duke, senior author of the study.
"The findings suggest for the first time that the fungus has developed a novel type of sexual cycle, allowing sexual reproduction between members of the same mating type," he added. "That ability might confer an advantage for the fungus because patients infected with it predominantly harbor a single mating type, reducing the possibility of normal fungal sexual reproduction."
The potentially life-threatening fungus C. neoformans invades the central nervous system to cause disease, most commonly in immune-compromised patients such as organ transplant recipients and cancer patients -- whose immune systems are crippled by immunosuppressive drugs or chemotherapy -- and people with HIV/AIDS. The fungus' global importance as a health threat has therefore risen in parallel with the increased use of such therapies and with the worldwide HIV/AIDS pandemic.
In plants and animals, sexual identity is governed by sex chromosomes. In fungi, however, sexual identity is determined by so-called