Chitin Synthase Gene Expression in the Dimorphic Fungus Penicillium marneffei

Abstract

Penicillium marneffei is a pathogenic fungus endemic to Southeast Asia. It is the only Penicillium species that displays thermally dependent dimorphism. At 25° C, the fungus grows as a filamentous mold, but develops as a fission yeast at 37° C. The pathogenicity of P. marneffei is associated with this dimorphism. Presumably, dimorphism directly reflects changes in the cell wall structure. A major fungal cell wall component is chitin. Seven chitin synthase genes have been identified in P. marneffei and each is presumed to serve different functions during cell wall development, hyphal growth, conidiophore development, and septum formation. Determining the temporal and spatial expression of these chs genes would provide a better understanding into the growth and morphogenesis of P. marneffei. Hence, using a reverse-transcription polymerase chain reaction and a reverse-transcription quantitative polymerase chain reaction, the expression of each chs orthologue was assessed after 1 and 5 days of incubation of the fungus at 25° C and 37° C under conditions that do not induce conidiogenesis. The results indicate that some chs genes are differentially expressed, some appear constitutively expressed at various levels, and some are not expressed under the experimental conditions employed. These patterns of expression appear to correlate with the purported function of each gene and the developmental phase examined.