Abstract
Coccidioides is a primary fungal pathogen of humans, causing life-threatening respiratory disease known as coccidioidomycosis (Valley fever) in immunocompromised individuals. Recently, Sharpton et al (2009) found that the deuterolysin (M35) family genes were significantly expanded in both the Coccidioides genus and in U. reesii, and that Coccidioides has acquired three more M35 family genes than U. reesii. In the present work, phylogenetic analyses based on a total of 28 M35 family genes using different alignments and tree-building methods consistently revealed five clades with high nodal supports. Interestingly, likelihood ratio tests suggested significant differences in selective pressure on the ancestral lineage of three additional duplicated M35 family genes from Coccidioides species compared to the other lineages in the phylogeny, which may be associated with novel functional adaptations of M35 family genes in the Coccidioides species, e.g., recent pathogenesis acquisition. Our study adds to the expanding view of M35 family gene evolution and functions as well as establishes a theoretical foundation for future experimental investigations.
Highlights
Coccidioides, a type of dimorphic fungi in the order Onygenales, is composed of two closely related species, Coccidioides posadasii and Coccidioides immitis [1,2]
For the other six fungal species, one M35 family gene each was predicted from H. capsulatum, P. brasiliensis and F. graminearum, while two genes each were identified from B. dermatitidis, N. crassa and P. odorum (Table 1 and Figure 2)
We found that the M35 family genes are significantly expanded in Coccidioides and U. reesii compared with the other fungal species examined
Summary
Coccidioides, a type of dimorphic fungi in the order Onygenales, is composed of two closely related species, Coccidioides posadasii and Coccidioides immitis [1,2] They are primary fungal pathogens of humans, which can cause life-threatening respiratory disease known as coccidioidomycosis (Valley fever) in the immunocompromised individuals [3,4,5,6]. They infect about 150,000 people annually in the United States [4], and have been listed as one of the ‘‘U.S Health and Human Services Select Agents’’ of bioterrorism [7]. By comparing the genome sequences of Coccidioides species and U. reesii, Sharpton et al [16] found that the M35 family genes, i.e., Mep to Mep, experienced gene duplication events before the divergence of Coccidioides genus and U. reesii, and Coccidioides acquired three additional Mep genes (Mep2like, Mep7-like and Mep8-like) after it diverged from U. reesii [16]
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