Fig. 2

The model of biosynthesis, translocation, and secretion of effectors in M. oryzae. During the early stage of M. oryzae-rice interaction, the protein kinase MoOsm1 is phosphorylated and enters the nucleus as monomers upon recognizing host ROS. Then, MoOsm1 phosphorylates the TF MoAtf1 and dissociates MoAtf1 from a transcriptional repressor MoTup1, leading to the transcription of antioxidant genes in response to host ROS accumulation. MoAtf1 simultaneously activates the expression of phosphatase MoPtp1/2, which in turn dephosphorylates MoOsm1. After dephosphorylation, MoPtp1/2 exits from the nucleus and forms dimers in the cytosol. Meanwhile, the cytoplastic MoYvh1 accelerates the maturation of ribosomes to facilitate the biosynthesis of effectors in response to external ROS. The synthesized effectors are further processed in ER, where the signal peptide of effectors is cleaved and the N-terminal tri-peptide motif is thus exposed to ER membrane complex protein MoErv29 for further sorting into distinct vesicles. When effectors are encapsulated in vesicles, de-polymerization factor MoSwa2 interacts with COPII vesicle component protein MoSec24-2 to regulate the depolymerization of COPII vesicles and promote the fusion of COPII with the target membrane. MoErg4 regulates ergosterol biosynthesis and plasma membrane integrity, which are important for lipid raft formation and the interaction of MoSso1 and MoSnc1. They collectively modulate BIC development and cytoplasmic effector protein secretion. As a result, the effectors are secreted into apoplastic space or host cytoplasm, which subsequently suppresses host immune responses