418회 Comparative study on CO2 sensing and sexual development of Asperg…

418회 (2008. 9. 25.)

연사: 한 갑 훈, 우석대학교 제약공학과

제목: Comparative study on CO2 sensing and sexual development of Aspergillus fumigatus and Aspergillus nidulans  

Abstract 

Aspergillus fumigatusis known as the primary causative agent of aspergillosis, which is an opportunistic infectious fungal disease mainly localized in the respiratory system of human and animals. Although the patients suffered from the invasive aspergillosis as well as the allergic diseases are getting increased, molecular mechanism of A. fumigatusi nfection has not been well elucidated yet. The hypoxic condition is important to A. fumigatus because the environment of host cells isusually maintained as hypoxic condition. Currently, A. fumigatus has no known sexual development process, while a homothallic fungus Aspergillus nidulans, which is a very close relative of A. fumigatus, undergoes complete sexual development process. Furthermore, in A. nidulans, hypoxic condition is one of the most important environmental factor for generating fruit bodies or cleistothecia. To study relationship between hypoxic stress condition and fungal development and virulence in a high-throughput manner, DNA microarray experiments were performed using A. fumigatus and A. nidulans 70-mer oligo microarray chips. As a result, we identified that the genes encoding carbonic anhydrase(CA), which mediate reversible interconvertion between gaseous CO2 and bicarbonate ions (HCO3-) for maintaining cellular homeostasis, are up-regulated in hypoxic condition. CAs are ubiquitous and grouped into four general classes that are a-, b-, g-, and d-CA. Since A. fumigatus is a major fungal pathogen causing invasive aspergillosis in immunocompromised patients, adaptation of different CO2 concentration, probably mediated by CAs, could be important. Genome sequence of A. fumigatus allowed us to identify three conserved b-CAs designated as cafA (CA in A. fumigatus), cafB and cafC, respectively. All three CAs are expressed during the life cycle. Similarly, A. nidulans genome also contains three CA orthologs which are named as canA (CA in A. nidulans), canB and canC. Characterization of these genes associated with hypoxic stress will give an important clue of CO2 sensing and developmental progresses in filamentous fungi.