We use the Neurospora crassa asexual and sexual reproduction cycles as model systems to understand cell differentiation. A hyperoxidant state (HO) was found at the start of each morphogenetic transition during asexual spore formation (conidiation). Consequences of a HO are growth arrest, protein oxidation and degradation, induction of an antioxidant response and cell differentiation. Once in a differentiated state, growth can restart. We aim to determine the molecular switch that regulates growth arrest and restart. ras-1bd mutant and superoxide dismutase null strains alternate between growth and conidiation. Addition of antioxidants abolished this cycle while oxidants shortened its period in both strains; they also showed enhanced production of ROS and displayed increased aerial hyphae formation. The objective is to test whether RAS-1 acts as a regulatory switch that governs growth and development through the activity of different MAPK cascades and the cAMP pathway. We will test this model by: measuring NOX activity and NOX protein interactions, determining cAMP levels and the phosphorylation state of MAK-2 and OS-2, assaying proteins interactions with NCR-1, AC and RAS-1 and identifying of proteins with cysteines that are transiently oxidized during oxidative stress and cell differentiation, one of which might be RAS-1 itself.
RAS-1 model for growth and cell development in N. crassa