Systematic functional analysis of calcium-signalling proteins in the genome of the rice-blast fungus, Magnaporthe oryzae, using a high-throughput RNA-silencing system

MoCRZ1, a gene encoding a calcineurin-responsive transcription factor, regulates fungal growth and pathogenicity of Magnaporthe oryzae

Ca(2+)-dependent signaling plays important roles in cellular development and metabolism in fungi. Pharmacological and molecular evidence clearly indicates that Ca(2+)-dependent signaling is required for infection-related development and pathogenicity in the rice blast fungus Magnaporthe oryzae. However, little information is available on downstream regulators in the Ca(2+)-dependent signaling pathway. To understand the role of a calcineurin-dependent transcription factor in the rice blast fungus, an ortholog of Saccharomyces cerevisiae CRZ1 in M. oryzae, MoCRZ1, was identified and functionally characterized. The Deltamocrz1 mutant exhibited impaired growth in the presence of Ca(2+) ions or cell wall perturbing agents. The Deltamocrz1 mutant also showed reduced conidiation and reduced pathogenicity, which is mainly due to a defect in host penetration. MoCRZ1 fused to EGFP was trans-localized into the nucleus in a Ca(2+)/calcineurin-dependent manner. The MoCRZ1 gene is also required for the calcineurin-dependent transcriptional induction of FKS1, a gene encoding a beta-1,3 glucan synthase, CHS2 and CHS4, genes encoding two chitin synthases, and PMC and PMR gene families encoding P-type ATPases in response to Ca(2+). These results suggest that MoCRZ1 is a downstream regulator in Ca(2+)-dependent signaling for pathogenicity in M. oryzae, and its biochemical mechanisms are well conserved among fungal species.

Investigation of the biological roles of autophagy in appressorium morphogenesis in Magnaporthe oryzae

Magnaporthe oryzae has been used as a primary model organism for investigating fungus-plant interaction. Many researches focused on molecular mechanisms of appressorium formation to restrain this fungal pathogen. Autophagy is a very high conserved process in eukaryotic cells. Recently, autophagy has been considered as a key process in development and differentiation in M. oryzae. In this report, we present and discuss the current state of our knowledge on gene expression in appressorium formation and the progress in autophagy of rice blast fungi.

RNA interference: roles in fungal biology

The discovery of RNA interference (RNAi) has been the major recent breakthrough in biology. Only a few years after its discovery, RNAi has rapidly become a powerful reverse genetic tool, especially in organisms where gene targeting is inefficient and/or time-consuming. In filamentous fungi, RNAi is not currently used as widely as is gene targeting by homologous recombination that works with practical efficiencies in most model fungal species. However, to explore gene function in filamentous fungi, RNAi has the potential to offer new, efficient tools that gene disruption methods cannot provide. In this review, possible advantages and disadvantages of RNAi for fungal biology in the postgenomics era will be discussed. In addition, we will briefly review recent discoveries on RNAi-related biological phenomena (RNA silencing) in fungi.

Genomes, free radicals and plant cell invasion: recent developments in plant pathogenic fungi

This review describes current advances in our understanding of fungal-plant interactions. The widespread application of whole genome sequencing to a diverse range of fungal species has allowed new insight into the evolution of fungal pathogenesis and the definition of the gene inventories associated with important plant pathogens. This has also led to functional genomic approaches to carry out large-scale gene functional analysis. There has also been significant progress in understanding appressorium-mediated plant infection by fungi and its underlying genetic basis. The nature of biotrophic proliferation of fungal pathogens in host tissue has recently revealed new potential mechanisms for cell-to-cell movement by invading pathogens.

Silencing the crowd: high-throughput functional genomics in Magnaporthe oryzae

A new high-throughput RNA-silencing system has been developed for use in the rice blast fungus Magnaporthe oryzae, allowing rapid generation of transformants in which individual genes have been silenced. Development of this system will allow large-scale functional analysis of genes in the fungus to define the cellular processes required for plant infection and disease symptoms. Functional analysis of 37 genes predicted to be involved in calcium signalling was carried out by RNA silencing to validate the new strategy and has provided new insight into the role of calcium-mediated signal transduction in plant pathogenic fungi.