Mycoses refer to infections caused by different fungal infections. Some mycoses can be defeated by the hosts themselves attributed to the functional immune systems before severe symptoms appear. However, in immune-compromised patients, including those suffering from AIDS or receiving chemotherapies, those mycoses become lethal. They are called opportunistic systemic mycoses. Among them, two types of the most deadly mycoses, especially for AIDS patients in Southeast Asia, are cryptococcsis and penicillosis, caused by Cryptococcus neoformans (C. neoformans) and Penicillium marneffei (P. marneffei), respectively. Both of them have their own virulence factors to enhance their pathogenicities and survival in hosts. Active research to explore these virulence factors in these two funguses is ongoing. Two proteins from these two pathogens were found to be putative novel virulence factors, MP1p from P. marneffei, and CPL1 from C. neoformans. Collaborators have successfully found that MP1p strongly bound arachidonic acids (AA), the sole precursor of paracrine signaling molecules essential to the onset of inflammatory responses, by various functional studies. This led to the hypothesis that MP1p might be able to suppress inflammatory responses and subsequent immune responses via removal of AA from macrophages engulfed P. marneffei. In this work, X-ray crystal structures of MP1p’s ligand-binding domain 2 (LBD2) from P. marneffei (strain MP1) overexpressed in E. coli, in complex with one and two AA molecules, were successfully solved by molecular replacement method. The resolutions were up to 1.45 Å and 1.50 Å respectively. These structures revealed detailed interactions between MP1p-LBD2 and AA.A possible ligands-dependent dimer-monomer transition in LBD2 was also revealed by both analytical size exclusion chromatography and crystallography. Full length CPL1 overexpressed in yeast was also successfully purified and crystallized. A 3.0 Å native dataset was collected. Heavy atoms derivatives of the crystals would be produced in order to solve the structure via experimental phasing methods. The structural determination of these virulence factors may provide molecular bases at atomic resolution for the developments of drugs targeting MP1p and CPL1 by structure-based drug design to treat, particularly, penicillosis and cryptococcsis in immune-compromised patients. / published_or_final_version / Physiology / Master / Master of Philosophy

Thesis (M. Phil.)--University of Hong Kong, 2009. / Includes bibliographical references (leaves 111-131) Also available in print.

Presented as Thesis (Ph. D.)--University of Wisconsin--Madison, 1932. / Caption title. Reprinted from Phytopathology, vol. XXIII, no. 2 (Feb. 1933). Includes bibliographical references (leaves 153-154).

Thesis (M.S.)--University of Wisconsin--Madison, 1965. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

No description available.

published_or_final_version / abstract / Microbiology / Doctoral / Doctor of Philosophy

published_or_final_version / Microbiology / Master / Master of Philosophy

Plants produce complex mixtures of secondary metabolites to defend themselves from pathogens. Among these defenses are metabolites produced de novo, phytoalexins, and constitutive metabolites, phytoanticipins. As a counter-attack, pathogenic fungi are able to transform such plant defenses utilizing detoxifying enzymes. This thesis investigates the metabolism of two important cruciferous phytoalexins (brassinin (33) and camalexin (39)) by the phytopathogenic fungus Botrytis cinerea and the metabolism of cruciferous phytoanticipins (glucosinolates and derivatives) by three economically important fungi of crucifers Alternaria brassicicola, Rhizoctonia solani and Sclerotinia sclerotiorum to investigate their role in cruciferous defense. In the first part of this thesis, the transformations of brassinin (33) and camalexin (39) by B. cinerea were investigated. During these studies a number of new metabolites were isolated, their chemical structures were determined using spectroscopic techniques, and further confirmed by synthesis. Camalexin (39) was transformed via oxidative degradation and brassinin (33) was hydrolyzed to indoly-3-methanamine (49). The metabolic products did not show detectable antifungal activity against B. cinerea, which indicated that these transformations were detoxification processes. Camalexin (39) was found to be more antifungal than brassinin (33). In the second part of this thesis, the metabolism of glucobrassicin (86), 1-methoxyglucobrassicin (87), 4-methoxyglucobrassicin (90), phenylglucosinolate (65), and benzylglucosinolate (66), the corresponding desulfoglucosinolates and derivatives by three fungal pathogens (A. brassicicola, R. solani and S. sclerotiorum) was investigated and their antifungal activity against the same pathogens was tested. Aryl iii glucosinolates 65 and 66 were metabolized by A. brassicicola but not by R. solani or S. sclerotiorum, whereas indolylglucosinolates were not metabolized by any pathogen. Indolyl desulfoglucosinolates (159 and 233) were transformed by R. solani and S. sclerotiorum to the corresponding carboxylic acids and indolyl acetonitriles 40, 102, and 103 were also metabolized to the corresponding carboxylic acids by all pathogens. None of the glucosinolates or their desulfo derivatives showed antifungal activity, but some of their metabolites showed low to very high antifungal activities. Among these metabolites, diindolyl-3-methane (113) showed the highest antifungal activity, and benzyl isothiocyanate (170) showed higher inhibitory effect against R. solani and S. sclerotiorum, but did not inhibit the growth of A. brassicicola. The cell-free extracts of A. brassicicola, R. solani, and S. sclerotiorum were tested for myrosinase activity against several glucosinolates. The cell-free extracts of mycelia of A. brassicicola displayed higher myrosinase activity for sinigrin (131), phenyl and benzyl glucosinolates 65 and 66, but lower activities for glucobrassicin (86) and 1-methoxyglucobrassicin (87); no myrosinase activity was detected in mycelia of either R. solani or S. sclerotiorum.

published_or_final_version / Microbiology / Doctoral / Doctor of Philosophy

No description available.