Organisms of (+) mating type have the MAT1-1 idiomorph of the mating locus, while organisms of (-) mating type have the MAT1-2 idiomorph of the mating locus [2]. The fungus is pathogenic, and organisms of (-) mating type may be associated with increased virulence. The organism causes acute pulmonary disease when inhaled into the lung [3–5]. Individuals may also develop the disseminated form of the disease, which is usually controlled by activation of cell-mediated immunity in immune-competent individuals [4, 6]. Organisms of (-) mating type are found more frequently in samples from patients with pulmonary

histoplasmosis; however, organisms of both mating types are represented equally in samples from patients with severe disseminated histoplasmosis and in environmental samples [7, 8]. It is unknown whether

the (-) mating type strain predominates VX-770 nmr in clinical samples due to host factors, or differences between organisms of opposite mating type. A single study examining virulence of (+) and (-) mating type strains has been reported; however, interpretation is limited by the inability to compare congenic strains of H. capsulatum [9]. Mating occurs under appropriate conditions in the mycelial phase when hyphae arising from organisms of opposite mating type appose and generate a complex structure comprising of a net of short branching hyphae covered with coiled surface hyphae. Within this specialized Ceritinib mw closed structure, the cleistothecium, cytoplasmic and nuclear fusion occur followed by successive rounds of meiosis and mitosis generating sac-like asci containing 8 ascospores, the end-product of sexual replication. Generation of congenic strains in H. capsulatum is challenging due to the low frequency of homologous gene targeting in the organism [10], and because the organism rapidly loses mating ability in culture [7]. This limits the feasibility of gene replacement or backcrossing as methods for generating congenic strains. If the loss of mating competency could be overcome in

laboratory strains of H. capsulatum, a variety of classical genetics techniques could be developed for use in this organism, including congenic strain construction. Understanding Vorinostat in vivo the molecular mechanisms that regulate mating could lead to the restoration of mating ability in laboratory strains of H. capsulatum. Through this work, we generated a strain of H. capsulatum that can be used to examine molecular correlates of mating. Regulation of mating in fungi requires integration of multiple pathways in a complex developmental program. The pheromone response MAP kinase pathway is a central pathway in the mating response of many fungi [11]. In the model fungus Saccharomyces cerevisiae, this pathway allows yeasts to sense a mating partner, and coordinates appropriate responses such as G1 arrest [12, 13].