Evidence for a phylogenetic connection between Coccidioides immitis and Uncinocarpus reesii (Onygenaceae)

Abstract

Coccidioides immitis is an anomaly amongst the human systemic fungal pathogens. Its unique parasitic cycle has contributed to confusion over its taxonomy. Early investigators mistakenly suggested that the pathogen is a protist, while others agreed it to be a fungus but placed it in four different divisions of the Eumycota. The taxonomy of C. immitis is still unresolved. Ultrastructural examinations of its parasitic and saprobic phases have revealed features that are diagnostic of the ascomycetous fungi. Moreover, striking similarities between the kind of asexual reproduction (i.e. arthroconidium formation) of this pathogen and certain anamorphic and teleomorphic members of the genus Malbranchea have suggested a close relationship. Teleomorphs of these Malbranchea species are members of the Onygenaceae (Order, Onygenales). This family also includes teleomorphs of two human respiratory pathogens, Histoplasma capsulatum and Blastomyces dermatitidis. Although the 185 rRNA gene sequences (1713 bp) of these two pathogenic forms differ from that of C. immitis by only 35 and 33 substitutions, respectively, their mode of conidiogenesis is characterized by production of solitary aleurioconidia rather than alternate arthroconidia. In this study we have used characters derived from biochemical, immunological and molecular analyses to compare relatedness between C. immitis, H. capsulatum, B. dermatitidis, and six non-pathogenic species of Malbranchea (the Malbranchea states of Uncinocarpus reesii and Auxatthron zuffianum, as well as M. albolutea, M. dendritica, M. filamentosa and M. gypsea). Evidence is presented which supports inclusion of C. immitis in the Onygenaceae, and indicates that a close phylogenetic relationship exists between the Malbranchea state of U. reesii and this respiratory pathogen.

Evolution of the Mating Type Locus: Insights Gained from the Dimorphic Primary Fungal Pathogens Histoplasma capsulatum , Coccidioides immitis , and Coccidioides posadasii

“…1). This also holds true when we compare the structures found in the genome project at the Broad Institute of the next closest sequenced relative, Uncinocarpus reesii (30), which encodes a MAT1-1 ␣-box idiomorph. As seen for C. immitis, C. posadasii, A. fumigatus, and A. oryzae, this member of the Onygenales has the COX13-APN2-MAT-SLA2 mating type locus region arrangement.…”

“…Genomic DNA was isolated using a QIAGEN genomic DNA kit according to the manufacturer's instructions. The genomic DNA was isolated from Coccidioides immitis and Coccidioides posadasii mycelia grown for 4 days in glucose-yeast extract liquid medium (Difco) as previously described (30).…”

Concordance of gene genealogies reveals reproductive isolation in the pathogenic fungus Coccidioides immitis

“…For chitin synthase, serine proteinase, and dioxygenase, primers were designed based on sequences of C. immitis available in GenBank, accession nos. L28067, M81863, and L38493 (16,18,19), respectively; for chitinase, they were designed based on an unpublished sequence of C. immitis kindly supplied by G. Cole (Medical College of Ohio, Toledo) and T. Kirkland (University of California School of Medicine, San Diego); and for orotidine decarboxylase, they were designed based on conserved regions of sequences of Aspergillus niger, A. nidulans, and Penicillium chrysogenum (ref. 17; PCR primer sequences can be obtained from the authors).…”

Recent Advances in Our Understanding of the Environmental, Epidemiological, Immunological, and Clinical Dimensions of Coccidioidomycosis

“…Their closest relative for which a genome sequence is currently published, determined by both phylogenetic analysis and morphology, is Uncinocarpus reesii (Onygenaceae), a keratinophilic saprotroph (6,7). Whereas U. reesii has a known sexual life cycle (7,8), the sexual cycle of Coccidioides remains undescribed.…”