Northern Illinois University
Survival of fungal pathogens depends on the ability of the fungus to evade the host cell immune system. Host cells produce toxic amount of chemicals to prevent pathogens, such as fungi, from invading and causing disease. These host reactive chemicals can harm the fungus by damaging its DNA, inactivating proteins and altering lipids. Oxygen- and nitrogen-containing compounds are among the most common reactive species encountered in various life forms. High levels of reactive species such as nitric oxide and hydroxyl radicals cause stress in fungi. However, low levels of nitric oxide can also act as an important signaling molecule in biological systems. Both eukaryotic and prokaryotic cells have devised numerous mechanisms to counteract the stress imposed by high level of reactive nitrogen and oxygen species which includes enzymatic and non enzymatic mechanisms. However, very little is known about the nitrosative and oxidative stress response in fungi. This thesis includes the study of (1) the role of nitric oxide and flavohemoglobin genes in Aspergillus nidulans sexual development and mycotoxin production, and (2) the role of the velvet gene ( veA ) in oxidative stress response in Aspergillus flavus .