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J Med Microbiol 57 (2008), 1322-1328; DOI: 10.1099/jmm.0.2008/002832-0
© 2008 Society for General Microbiology
ISSN 0022-2615

Molecular analysis of the Penicillium marneffei glyceraldehyde-3-phosphate dehydrogenase-encoding gene (gpdA) and differential expression of gpdA and the isocitrate lyase-encoding gene (acuD) upon internalization by murine macrophages

Sophit Thirach1, Chester R. Cooper, Jr2 and Nongnuch Vanittanakom1

1 Department of Microbiology, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand

2 Department of Biological Sciences, Youngstown State University, Youngstown, OH, USA

Correspondence
Nongnuch Vanittanakom
drnongnuch{at}gmail.com

Received April 25, 2008
Accepted July 9, 2008

Penicillium marneffei is an intracellular dimorphic fungus that can cause a fatal disseminated disease in human immunodeficiency virus-infected patients. The factors that affect the pathogenicity of this fungus remain unclear. Here, we report the isolation and characterization of the gpdA cDNA and genomic clones encoding glyceraldehyde-3-phosphate dehydrogenase (GAPDH) in P. marneffei. Phylogenetic analysis of GAPDH amino acid sequences demonstrated the evolutionary relationship of P. marneffei to other fungi, including the intracellular pathogen Ajellomyces capsulatus. To assess the central importance of phagocytic cells in defence against P. marneffei infection, we used Northern blotting to investigate the response of the isocitrate lyase-encoding gene (acuD) and gpdA to nutrient deprivation inside macrophages. The results revealed that after macrophage internalization, the gene involved in the glyoxylate cycle, acuD, showed higher expression levels as early as 2 h from the start of co-incubation, and the differential expression could be observed again at 8 h after infection. In contrast, the expression of gpdA was downregulated in the yeast phase, as well as during macrophage infection after 2, 4 and 8 h of infection. The induction of P. marneffei acuD was shown to be coordinated with the downregulation of the glycolytic gpdA gene, implying that the cytoplasmic environment of macrophages is deficient in glucose and the glyoxylate pathway could be used by this pathogen to allow subsistence on two-carbon compounds within the host cell following its intracellular persistence.

Abbreviations: GAPDH, glyceraldehyde-3-phosphate dehydrogenase.

The GenBank/EMBL/DDBJ accession numbers for the cDNA and genomic DNA sequences of gpdA are EF987476 and EU000324, respectively.

Nucleotide and deduced amino acid sequences of the P. marneffei gpdA gene in this study are available as supplementary data with the online version of this paper.






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