MoMih1 is indispensable for asexual development, cell wall integrity, and pathogenicity of Magnaporthe oryzae

Abstract

Asexual spore serves as essential inoculum of rice blast during the disease cycle, and differentiation of young conidium from conidiophore is intimately regulated by cell cycle. Mih1 encodes a dual-specificity phosphatase that involved in the G2/M transition of the mitotic cell cycle by regulating the Cdk1 activity in eukaryotes. Till now, the roles of Mih1 homologue, however, remain unclear in Magnaporthe oryzae. We here functionally characterized the Mih1 homologue MoMih1 in M. oryzae. MoMih1 is localized to both the cytoplasm and nucleus and can physically interact with the CDK protein MoCdc28 in vivo. Loss of MoMih1 led to delayed nucleus division and a high level of Tyr15 phosphorylation of MoCdc28. The MoMih1 mutants showed retarded mycelial growth with a defective polar growth, less fungal biomass, and shorter distance between diaphragms, compared with the KU80. Asexual reproduction altered in MoMih1 mutants, with both abnormal conidial morphogenesis and decreased conidiation. The MoMih1 mutants severely attenuated the virulence to host plants due to the impaired ability of penetration and biotrophic growth. The incapability of scavenging of host-derived reactive oxygen species, which was possibly ascribed to the severely decreased extracellular enzymes activities, were partially associated with deficiency of pathogenicity. Besides, the MoMih1 mutants displayed also improper localization of retromer protein MoVps26 and polarisome component MoSpa2, and defects of cell wall integrity (CWI), melanin pigmentation, chitin synthesis, and hydrophobicity. In conclusion, our results demonstrate that MoMih1 plays pleiotropic roles during fungal development and plant infection of M. oryzae.

Insight into the adaptation mechanisms of high hydrostatic pressure in physiology and metabolism of hadal fungi from the deepest ocean sediment

“…In fungi, the septum is initially formed by a series of accumulations of actin, which recruits myo-2 to produce contractile force; then, protein bud4 gathers bud3 and rho-4 to determine the exact location for contractile actomyosin ring (CAR) formation, and finally, the cell wall is constructed ( 47 , 48 ). Here, we found the septum formation-related genes were differently regulated under elevated HHP (downregulated in 20 MPa while not significantly expressed in 40 MPa; Table S3), including myosin complex, rho family (a signaling protein that presumably affects septins, formins, and p21-activated kinases), and gene mih1 (a previous report showed that a shorter distance between the septa was observed in mih1 mutants [ 49 ]). Consequently, we assumed that under 20 MPa, myosin proteins and rho complex were not yet activated to find the exact location for CAR formation; then, they randomly distributed within the hypha and directly contracted; as a result, irregular and growing numbers of septa were formed ( Fig.…”

“…Here, we found that the morphogenesis checkpoint regulated by hog1 was the dominant “control” part, which made the G2/M phase of the cell cycle unable to proceed normally. Besides, gene mih1 was downregulated, a gene that encoded a dual-specificity phosphatase and involved in the G2/M transition of the mitotic cell cycle by regulating the Cdk1 activity in eukaryotes ( 49 ). We also detected another dramatically reduced expression of hsl7 , a protein that binds to swe1.…”