The fine-tuned expression dynamics of the effector genes are pivotal for the transition from vegetative growth to host colonization of pathogenic filamentous fungi.  However, mechanisms underlying the dynamic regulation of these genes remain largely unknown.  Here, through comparative transcriptome and chromatin immunoprecipitation sequencing (ChIP-seq) analyses of the methyltransferase PoKmt6 in rice blast fungus Pyricularia oryzae (syn. Magnaporthe oryzae), we found that PoKmt6-mediated H3K27me3 deposition was enriched mainly at fast-evolving regions and contributed to the silencing of a subset of secreted proteins (SP) and transposable element (TE) families during the vegetative growth of P. oryzae.  Intriguingly, we observed that a group of SP genes, which were depleted of H3K27me3 modification, could also be silenced via the H3K27me3-mediated repression of the nearby TEs.  In conclusion, our results indicate that H3K27me3 modification mediated by PoKmt6 regulates the expression of some SP genes in fast-evolving regions through the suppression of nearby TEs.

The peroxisomal matrix oxidase, catalase and peroxidase are imported peroxisomes through the shuttling receptors, which regulates the cellular oxidative homeostasis and function.  Here, we report that PTS1 shuttling receptor FvPex5 is involved in the localization of PTS1, utilization of carbon sources and lipids, elimination ROS, cell wall stress, conidiation, fumonisin B₁ (FB₁) production, and virulence in maize pathogen Fusarium verticillioides.  Significantly, differential expression of PTS1-, PTS2-, PEX- and FB₁ toxin-related genes in wild type and ΔFvpex5 mutant were examined by RNA-Seq analyses and confirmed by RT-PCR assay.  In addition, different expression of PTS1 and PTS2 genes of the ΔFvpex5 mutant were enriched in diverse biochemical pathways, such as carbon metabolism, nitrogen metabolism, lipid metabolism and the oxidation balance by combining GO and KEGG annotations.  Overall, we showed that FvPex5 is involved in the regulation of genes associated with PTS, thereby affecting the oxidation balance, FB₁ and virulence in F. verticillioides.  The results help to clarify the functional divergence of Pex5 orthologs, and may provide a possible target for controlling F. verticillioides infections and FB₁ biosynthesis.

 

Genome dynamics of pathogenic organisms are driven by plant host and pathogenic organism co-evolution, in which pathogen genomes are used to overcome stresses imposed by hosts with various genetic backgrounds through generation of a range of field isolates.  This model also applies to the rice host and its fungal pathogen Magnaporthe oryzae.  To better understand genetic variation of M. oryzae in nature, the field isolate V86010 from the Philippines was sequenced and analyzed.  Genome annotation found that the assembled V86010 genome was composed of 1 931 scaffolds with a combined length of 38.9 Mb.  The average GC ratio is 51.3% and repetitive elements constitute 5.1% of the genome.  A total of 11 857 genes including 616 effector protein genes were predicted using a combined analysis pipeline.  All predicted genes and effector protein genes of isolate V86010 distribute on the eight chromosomes when aligned with the assembled genome of isolate 70-15.  Effector protein genes are located disproportionately at several chromosomal ends.  The Pot2 elements are abundant in V86010.  Seven V86010-specific effector proteins were found to suppress programmed cell death induced by BAX in tobacco leaves using an Agrobacterium-mediated transient assay.  Our results may provide useful information for further study of the molecular and genomic dynamics in the evolution of M. oryzae and rice host interactions, and for characterizing novel effectors and AVR genes in the rice blast pathogen.  

Nerve growth factor (NGF) binds to TrkA and forms a NGF/TrkA complex at the cell surface, which is then internalized into signaling endosomes and promotes neuronal survival and neurite outgrowth. The small GTPase Rab5 is reported to localize on the plasma membrane and early endosomes, regulating endosome fusion. It was reported that endogenous Rab5 function may need to be suppressed during NGF-induced neurite outgrowth and cell differentiation. Two Rab5 homologs (MoRab5A: MGG_06241 and MoRab5B:MGG_01185) were characterized from the rice blast fungus Magnaporthe oryzae, and MoRab5B was identified as the Rab5 ortholog promoting early endosomal fusion, while MoRab5A specialized to perform a non-redundant function in endosomal sorting. In this study, we examined whether MoRab5A and MoRab5B play different roles in NGF-induced neurite outgrowth and cell differentiation in PC12 cells (a rat pheochromocytoma cell line). Our data showed that MoRab5B is a negative regulator of NGF signaling and neurite outgrowth in PC12 cells, similar to human Rab5 (hRab5). MoRab5B:WT inhibits NGF signaling-dependent neurite outgrowth while the dominant-negative MoRab5B mutant (MoRab5B:DN) enhances NGF signaling and neurite outgrowth. In contrast, MoRab5A:WT and MoRab5A:DN both significantly promote NGF-induced neurite outgrowth, indicating that MoRab5B is more similar to hRab5 than MoRab5A in the regulation of NGF signal transduction.