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Exploring the Penicillium marneffei genome
Kwok-Yung Yuen1, Géraldine Pascal, Samson S Y Wong
1HKU-Pasteur Research Centre, 8 Sassoon Road, Hong Kong. kyyuen@hkucc.hku.hk
Abstract:
Penicillium marneffei is a dimorphic fungus that intracellularly infects the reticuloendothelial system of humans and bamboo rats. Endemic in Southeast Asia, it infects 10% of AIDS patients in this region. The absence of a sexual stage and the highly infectious nature of the mould-phase conidia have impaired studies on thermal dimorphic switching and host-microbe interactions. Genomic analysis, therefore, could provide crucial information. Pulsed-field gel electrophoresis of genomic DNA of P. marneffei revealed three or more chromosomes (5.0, 4.0, and 2.2 Mb). Telomeric fingerprinting revealed 6-12 bands, suggesting that there were chromosomes of similar sizes. The genome size of P. marneffei was hence about 17.8-26.2 Mb. G+C content of the genome is 48.8 mol%. Random exploration of the genome of P. marneffei yielded 2303 random sequence tags (RSTs), corresponding to 9% of the genome, with 11.7, 6.3, and 17.4% of the RSTs having sequence similarity to yeast-specific sequences, non-yeast fungus sequences, and both (common sequences), respectively. Analysis of the RSTs revealed genes for information transfer (ribosomal protein genes, tRNA synthetase subunits, translation initiation, and elongation factors), metabolism, and compartmentalization, including several multi-drug-resistance protein genes and homologues of fluconazole-resistance gene. Furthermore, the presence of genes encoding pheromone homologues and ankyrin repeat-containing proteins of other fungi and algae strongly suggests the presence of a sexual stage that presumably exists in the environment.
Insights
Genomic analysis of Penicillium marneffei, a fungus infecting AIDS patients, revealed its genome size and key genes. This study provides insights into fungal dimorphism and potential drug resistance mechanisms.
Area of Science:
- Mycology
- Genomics
- Infectious Diseases
Background:
- Penicillium marneffei is a dimorphic fungus endemic to Southeast Asia.
- It causes opportunistic infections, particularly in 10% of AIDS patients in the region.
- Challenges in studying its thermal dimorphism and host interactions stem from its asexual reproduction and infectious nature.
Purpose of the Study:
- To conduct genomic analysis of Penicillium marneffei to understand its biology.
- To identify genes related to thermal dimorphism, host-microbe interactions, and drug resistance.
- To investigate the potential for a sexual stage in Penicillium marneffei.
Main Methods:
- Pulsed-field gel electrophoresis (PFGE) was used to analyze genomic DNA.
- Telomeric fingerprinting was employed to estimate chromosome number and size.
- Random sequence tags (RSTs) were generated for genome exploration and gene identification.
Main Results:
- The genome size of Penicillium marneffei was estimated to be 17.8–26.2 Mb with a G+C content of 48.8 mol%.
- Analysis of 2303 RSTs revealed genes involved in information transfer, metabolism, and compartmentalization.
- Several multi-drug-resistance protein genes and fluconazole-resistance gene homologues were identified.
- Genes encoding pheromone homologues and ankyrin repeat proteins suggest a potential sexual stage.
Conclusions:
- Genomic analysis provides crucial insights into Penicillium marneffei.
- The identified genes offer targets for understanding fungal dimorphism and developing antifungal strategies.
- Evidence suggests the presence of a sexual stage, potentially existing in the environment.