Penicillium marneffei actin expression during phase transition, oxidative stress, and macrophage infection
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Penicillium marneffei is an opportunistic fungal pathogen that exhibits thermally regulated dimorphism. At 25°C, this fungus grows vegetatively as mycelia, but at 37°C or upon invasion of a host, a fission yeast form is established. Yet, despite increased numbers of molecular studies involving this fungus, the role of P. marneffei stress response-related proteins is not well characterized. Actin is one of the proteins that have been proposed to play a role not only in cell transition, but also in thermo-adaptation. Here, we report the isolation and characterization of the actin encoding gene, actA, from P. marneffei. Examination of the deduced amino acid sequence of the ActA protein revealed that it is closely related to Aspergillus nidulans and Aspergillus clavatus. Northern blot analysis of actin expression during the mycelium to yeast phase transition of P. marneffei showed that the actA transcripts were initially upregulated soon after shifting the incubation temperature from 25°C to 37°C, but subsequently decreased slightly and did not change during further growth or under stress conditions. When cultures were started with conidia, upregulation of actA gene was found to correlate with germ tube production at either 25°C or 37°C. However, the relative expression level of actA transcripts again showed no significant differences in different cell types (conidia, mycelium, and yeast cells) or during macrophage infection. These results suggest that actin may play an important role in the early stages of cellular development, but not in environmental stress responses.
KeywordsPenicillium marneffei Dimorphic fungus Actin Stress response Macrophage infection
This work was supported by a Royal Golden Jubilee PhD research assistant fellowship to AK from the Thailand Research Fund, the “National Research University” Project of the Thai Ministry of Education, and the Faculty of Medicine, Chiang Mai University. Additional support was provided by the University Research Council and the Office of Student Affairs at Youngstown State University. We thank Ms. Karen Stangl for critically reviewing the manuscript.
Conflic of interest
The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.
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