Differential Expression of Genes Encoding Secreted Proteins in Penicillium Marneffei

Abstract

Penicillium marneffei is a dimorphic pathogenic fungus endemic to Southeast Asia. It primarily infects individuals with compromised immunity, particularly those with AIDS. This fungus undergoes a dimorphic switch when shifted from growth at 25ðC to 37ðC. At 25ðC, P. marneffei grows as a mycelium, whereas at 37ðC this fungus develops as a single-celled yeast that reproduces by fission. The latter type of morphogenesis is associated with pathogenesis. Presumably, one or more of a subset of 37ðC induced genes that encode secreted proteins may play roles in pathogenesis. Fungal secreted proteins play an important biological role. Studies have revealed that some fungal secreted proteins are involved in pathogenesis. Therefore, uniquely secreted proteins in Penicillium marneffei have been putatively identified by computational analysis. Those secreted protein-encoding genes expressed solely at 37ðC are likely candidates to have roles in pathogenesis. Hence, determining differential expression of these genes and by extension the secreted proteins they encode, may provide an indication in the mechanism of virulence of P. marneffei as well as serve as possible drug targets. Using methods employing a reverse-transcription polymerase chain reaction (RT-PCR) and its related process, quantitative polymerase chain reaction (qPCR), the expression of genes encoding each secreted protein was assessed at 25ðC(mycelia phase) and at 37ðC (yeast phase). The resulting data demonstrated that there are two genes tentatively designated HP1 and HYD, respectively, within the subsets studied that are induced solely during the yeast phase. Conversely, two other genes, tentatively designated HP2 and HP5 are abundantly expressed in the mycelial phase. Interestingly, HYD is similar to a homolog found in Aspergillus orzaye. The gene in the latter fungus has been found to absorb to hydrophobic surfaces. This suggests that HYD may have a role in attachment during pathogenesis of P. marneffei. This o