Characterization of two infection‐induced transcription factors of Magnaporthe oryzae reveals their roles in regulating early infection and effector expression

Abstract

The initial stage of rice blast fungus, Magnaporthe oryzae, infection, before 36 h postinoculation, is a critical timespan for deploying pathogen effectors to overcome the host's defences and ultimately cause the disease. However, how this process is regulated at the transcription level remains largely unknown. This study functionally characterized two M. oryzae Early Infection-induced Transcription Factor genes (MOEITF1 and MOEITF2) and analysed their roles in this process. Target gene deletion and mutant phenotype analysis showed that the mutants Δmoeitf1 and Δmoeitf2 were only defective for infection growth but not for vegetative growth, asexual/sexual sporulation, conidial germination, and appressoria formation. Gene expression analysis of 30 putative effectors revealed that most effector genes were down-regulated in mutants, implying a potential regulation by the transcription factors. Artificial overexpression of two severely down-regulated effectors, T1REP and T2REP, in the mutants partially restored the pathogenicity of Δmoeitf1 and Δmoeitf2, respectively, indicating that these are directly regulated. Yeast one-hybrid assay and electrophoretic mobility shift assay indicated that Moeitf1 specifically bound the T1REP promoter and Moeitf2 specifically bound the T2REP promoter. Both T1REP and T2REP were predicted to be secreted during infection, and the mutants of T2REP were severely reduced in pathogenicity.Our results indicate crucial roles for the fungal-specific Moeitf1 and Moeitf2 transcription factors in regulating an essential step in M. oryzae early establishment after penetrating rice epidermal cells, highlighting these as possible targets for disease control.

An array of signal-specific MoYpd1 isoforms determines full virulence in the pathogenic fungusMagnaporthe oryzae

“…Thereby, RNA-Seq data analysis as the only basis can be problematic for several reasons. Most published fungal RNA-Seq data are not strand-specific, and transcripts frequently overlap between adjacent genes due to their high gene density (Cao et al 2022). Furthermore, choosing between sequencing technologies and a wide range of bioinformatic tools that perform similar tasks but have different advantages and disadvantages can be challenging (Mehmood et al 2020; Thind et al 2021).…”

“…Conidia of the wildtype strain 70-15, ΔMoypd1 and the respective MoYpd1p isoform-producing strains were harvested from 14-day-old cultures in order to assess virulence. Rice plants (CO39) were grown, as previously described, and treated by both drop and spray inoculation (Cao et al 2022; Kramer, Thines, and Foster 2009).…”

Pyricularia oryzae: Lab star and field scourge

“…Relatively few transcription factors regulating the infection programme of the blast fungus and, specifically, effector expression have been identified. Examples are the bZIP transcription factors BIP1 and MoEITF2, and the zinc finger transcription factor MoEITF1 that control distinct infection‐related gene networks (Cao et al., 2022 ; Lambou et al., 2024 ), as well as the WOPR box transcription factor MoWOR1 (syn. MoGTI1) that acts in P. oryzae like in numerous other pathogenic fungi as a central regulator of pathogenicity (Chen, Zhai, et al., 2014 ; Li et al., 2016 ).…”

Whole genome regulatory effect ofMoISW2and consequences for the evolution of the rice plant pathogenic fungusMagnaporthe oryzae

“…These sites are staggered cut palindromic target sites (Linheiro and Bergman 2008). In addition, TEs are involved in stress adaptation and host specialization in Verticillium dahliae (Faino et al 2016) as well as in the rice blast fungus Magnaporthe oryzae studied here (Chadha and Sharma 2014; Yoshida et al 2016) and should especially be needed when the host plant detects the fungus as a pathogen at the transition between the endophytic to necrotrophic infection phase of the fungus and thereafter (Cao et al 2022).…”