Role of Two Metacaspases in Development and Pathogenicity of the Rice Blast Fungus Magnaporthe oryzae

• Published in: mBio 2021-02, Vol.12 (1)
• Main Authors: Fernandez, Jessie, Lopez, Victor, Kinch, Lisa, Pfeifer, Mariel A, Gray, Hillery, Garcia, Nalleli, Grishin, Nick V, Khang, Chang-Hyun, Orth, Kim
• Format: Article
• Language: English
• Subjects: Host-Microbe Biology; Research Article
• ISSN: 2161-2129; 2150-7511
• DOI: 10.1128/mBio.03471-20

Rice blast disease caused by is a devastating disease of cultivated rice worldwide. Infections by this fungus lead to a significant reduction in rice yields and threats to food security. To gain better insight into growth and cell death in during infection, we characterized two predicted metacaspase proteins, MoMca1 and MoMca2. These proteins appear to be functionally redundant and can complement the yeast Yca1 homologue. Biochemical analysis revealed that metacaspases exhibited Ca -dependent caspase activity Deletion of both and in resulted in reduced sporulation, delay in conidial germination, and attenuation of disease severity. In addition, the double Δ mutant strain showed increased radial growth in the presence of oxidative stress. Interestingly, the Δ strain showed an increased accumulation of insoluble aggregates compared to the wild-type strain during vegetative growth. Our findings suggest that MoMca1 and MoMca2 promote the clearance of insoluble aggregates in , demonstrating the important role these metacaspases have in fungal protein homeostasis. Furthermore, these metacaspase proteins may play additional roles, like in regulating stress responses, that would help maintain the fitness of fungal cells required for host infection. causes rice blast disease that threatens global food security by resulting in the severe loss of rice production every year. A tightly regulated life cycle allows to disarm the host plant immune system during its biotrophic stage before triggering plant cell death in its necrotrophic stage. The ways navigates its complex life cycle remain unclear. This work characterizes two metacaspase proteins with peptidase activity in that are shown to be involved in the regulation of fungal growth and development prior to infection by potentially helping maintain fungal fitness. This study provides new insights into the role of metacaspase proteins in filamentous fungi by illustrating the delays in morphogenesis in the absence of these proteins. Understanding the mechanisms by which morphology and development promote its devastating pathogenicity may lead to the emergence of proper methods for disease control.