Exploration of whole-genome responses of the human AIDS-associated yeast pathogen Cryptococcus neoformans var grubii: nitric oxide stress and body temperature.

Cryptococcus neoformans var grubii is an opportunistic basidiomycete yeast pathogen that is a significant cause of HIV/AIDS-related deaths worldwide. We describe a whole-genome oligonucleotide microarray for this pathogen. These arrays have been used to elucidate the transcriptional responses of the genome to heat shock as well as to two conditions relevant to human infections: body temperature and nitric oxide (NO) stress produced by the NO donor DPTA-NONOate. This analysis revealed an NO-inducible C. neoformans-specific four-gene family that showed a highly similar transcriptional profile to that of FHB1, a previously described NO dioxygenase/flavohemoglobin required for virulence. NO treatment also induced genes involved in the synthesis of the antioxidant mannitol, a polyol that accumulates in the cerebrospinal fluid of infected patients. Exposure to NO also caused increased expression of the sole C. neoformans var grubii protein with HHE/hemerythrin cation binding motifs. Notably, a similar gene in E. coli, ytfE, has been shown to be NO-inducible and protects bacterial cells from killing by NO. Genes induced by NO were highly enriched for those repressed at 37 degrees C, indicating an unexpected interplay between temperature and NO regulation in this basidiomycete. Resources described here should facilitate future investigations of this lethal human yeast pathogen.