P-373 - Investigating the role of DUG1 in glutathione degradation by Magnaporthe oryzae during rice blast disease

Rice blast, caused by the fungus Magnaporthe oryzae, is a major global threat to rice cultivation. During infection, the fungus encounters oxidative stress from host-derived reactive oxygen species (ROS) and nutrient starvation. To infect, M. oryzae must neutralize ROS to avoid stronger plant defenses. However, the mechanisms of adaptation to these stresses during in planta growth remain unclear. We used reverse genetics to explore the glutathione (GSH) system's role in M. oryzae's stress adaptation and pathogenicity. GSH acts as a major antioxidant, protecting fungus from ROS and providing sulfur and nitrogen under nutrient starvation. It degrades primarily via the γ-glutamyl cycle, but an alternative pathway, the Dug1-Dug2-Dug3 complex, is known in yeast. DUG1 also operates independently as a dipeptidase. Although M. oryzae has a DUG1 homolog, its function is unknown. Using a PCR-based split marker technique, we disrupted, revealing its role in virulence. Mutants showed impaired biotrophic growth and limited cell-to-cell movement of invasive hyphae during live-cell imaging of detached rice leaves. DUG1 is also crucial for conidiation. Thus, DUG1 and likely the Dug1-Dug2-Dug3 complex are crucial for M. oryzae growth in host rice cells, and we are testing the hypothesis that this is due to a role in connecting GSH homeostasis with S source availability. Taken together, our findings underscore the critical role of GSH degradation in fungal development and infection, highlighting its potential as a target for antifungal strategies against rice blast and other plant diseases.