Protein disulfide isomerase MoPdi1 regulates fungal development, virulence, and endoplasmic reticulum homeostasis in Magnaporthe oryzae

Rice blast, caused by Magnaporthe oryzae,is a fungal disease that causes devastating damage to rice production worldwide. During infection, pathogens secrete effector proteins that modulate plant immunity. Disulfide bond formation catalyzed by protein disulfide isomerases (PDI) is essential for protein folding and maturation. However, the biological function of Pdi1 in M. oryzae has not yet been characterized. In this study, we identified the endoplasmic reticulum (ER)-located protein, MoPdi1, in M. oryzae. MoPdi1 regulates conidiation, cell wall stress, and pathogenicity of M. oryzae. Furthermore, the CGHC active sites in the a and a' redox domain of MoPdi1 were essential for the biological function of MoPDI1. Further tests demonstrated that MoPdi1 was involved in the regulation of ER stress and positively regulated ER phagy. We also found that MoPdi1 interacted with MoHut1. Deletion of MoPDI1 led to the bereft of MoHut1 dimerization, which depends on the formation of disulfide bonds. In addition, MoPdi1 affected the normal secretion of the cytoplasmic effector AVR-Pia. We provided evidence that MoHut1 is important for the vegetative growth, conidiation, and pathogenicity in M. oryzae. Therefore, our findings could provide a suitable target point for designing antifungal agrochemicals against rice blast fungus.