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Gene expression profiling during conidiation in the rice blast pathogen Magnaporthe oryzae.

ABSTRACT: Conidiation of phytopathogenic fungi is a key developmental process that plays a central role in their life cycles and in epidemics. However, there is little information on conidiation-induced molecular changes in the rice blast fungus Magnaporthe oryzae. As a first step to understand conidiogenesis in this fungus, we measured genome-wide gene expression profiles during conidiation using a whole genome oligonucleotide microarray. At a two-fold expression difference, approximately 4.42% and 4.08% of genes were upregulated and downregulated, respectively, during conidiation. The differentially expressed genes were functionally categorized by gene ontology (GO) term analysis, which demonstrated that the gene set encoded proteins that function in metabolism, cell wall biosynthesis, transcription, and molecule transport. To define the events of the complicated process of conidiogenesis, another set of microarray experiments was performed using a deletion mutant for MoHOX2, a stage-specific transcriptional regulator essential for conidial formation, which was expressed de novo in a conidiation-specific manner in M. oryzae. Gene expression profiles were compared between the wild-type and the ?Mohox2 mutant during conidiation. This analysis defined a common gene set that was upregulated in the wild-type and downregulated in the ?Mohox2 mutant during conidiation; this gene set is expected to include conidiation-related downstream genes of MoHOX2. We identified several hundred genes that are differentially-expressed during conidiation; our results serve as an important resource for understanding the conidiation, a process in M. oryzae, which is critical for disease development.

SUBMITTER: Kim KS

PROVIDER: S-EPMC3424150 | biostudies-literature | 2012

REPOSITORIES: biostudies-literature

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Gene expression profiling during conidiation in the rice blast pathogen Magnaporthe oryzae.

Kim Kyoung Su KS Lee Yong-Hwan YH

PloS one 20120821 8

Conidiation of phytopathogenic fungi is a key developmental process that plays a central role in their life cycles and in epidemics. However, there is little information on conidiation-induced molecular changes in the rice blast fungus Magnaporthe oryzae. As a first step to understand conidiogenesis in this fungus, we measured genome-wide gene expression profiles during conidiation using a whole genome oligonucleotide microarray. At a two-fold expression difference, approximately 4.42% and 4.08% ...[more]

PMID: 22927950

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Project description:BACKGROUND: Magnaporthe oryzae, the causal agent of blast disease of rice, is the most destructive disease of rice worldwide. The genome of this fungal pathogen has been sequenced and an automated annotation has recently been updated to Version 6 http://www.broad.mit.edu/annotation/genome/magnaporthe_grisea/MultiDownloads.html. However, a comprehensive manual curation remains to be performed. Gene Ontology (GO) annotation is a valuable means of assigning functional information using standardized vocabulary. We report an overview of the GO annotation for Version 5 of M. oryzae genome assembly. METHODS: A similarity-based (i.e., computational) GO annotation with manual review was conducted, which was then integrated with a literature-based GO annotation with computational assistance. For similarity-based GO annotation a stringent reciprocal best hits method was used to identify similarity between predicted proteins of M. oryzae and GO proteins from multiple organisms with published associations to GO terms. Significant alignment pairs were manually reviewed. Functional assignments were further cross-validated with manually reviewed data, conserved domains, or data determined by wet lab experiments. Additionally, biological appropriateness of the functional assignments was manually checked. RESULTS: In total, 6,286 proteins received GO term assignment via the homology-based annotation, including 2,870 hypothetical proteins. Literature-based experimental evidence, such as microarray, MPSS, T-DNA insertion mutation, or gene knockout mutation, resulted in 2,810 proteins being annotated with GO terms. Of these, 1,673 proteins were annotated with new terms developed for Plant-Associated Microbe Gene Ontology (PAMGO). In addition, 67 experiment-determined secreted proteins were annotated with PAMGO terms. Integration of the two data sets resulted in 7,412 proteins (57%) being annotated with 1,957 distinct and specific GO terms. Unannotated proteins were assigned to the 3 root terms. The Version 5 GO annotation is publically queryable via the GO site http://amigo.geneontology.org/cgi-bin/amigo/go.cgi. Additionally, the genome of M. oryzae is constantly being refined and updated as new information is incorporated. For the latest GO annotation of Version 6 genome, please visit our website http://scotland.fgl.ncsu.edu/smeng/GoAnnotationMagnaporthegrisea.html. The preliminary GO annotation of Version 6 genome is placed at a local MySql database that is publically queryable via a user-friendly interface Adhoc Query System. CONCLUSION: Our analysis provides comprehensive and robust GO annotations of the M. oryzae genome assemblies that will be solid foundations for further functional interrogation of M. oryzae.

Project description:As the causal agent of the blast disease, Magnaporthe oryzae is one of the most destructive fungal pathogens of rice. Histone acetylation/deacetylation is important for remodeling of chromatin superstructure and thus altering gene expression. In this study, two genes encoding histone deacetylases, namely, MoRPD3 and MoHST4, were identified and functionally characterized in M. oryzae. MoHst4 was required for proper mycelial growth and pathogenicity, whereas overproduction of MoRpd3 led to loss of pathogenicity, likely due to a block in conidial cell death and restricted invasive growth within the host plants. Green fluorescent protein (GFP)-MoRpd3 localized to the nucleus and cytoplasm in vegetative hyphae and developing conidia. By comparative transcriptomics analysis, we identified potential target genes epigenetically regulated by histone deacetylases (HDACs) containing MoRpd3 or MoHst4, which may contribute to conidia formation and/or conidial cell death, which is a prerequisite for successful appressorium-mediated host invasion. Taken together, our results suggest that histone deacetylases MoRpd3 and MoHst4 differentially regulate mycelial growth, asexual development, and pathogenesis in M. oryzae. IMPORTANCE HDACs (histone deacetylases) regulate various aspects of growth, development, and pathogenesis in plant-pathogenic fungi. Most members of HDAC classes I to III have been functionally characterized, except for orthologous Rpd3 and Hst4, in the rice blast fungus Magnaporthe oryzae. In this study, we assessed the function of MoRpd3 and MoHst4 by reverse genetics and found that they differentially regulate M. oryzae vegetative growth, asexual development, and infection. Particularly, MoRpd3 negatively regulates M. oryzae pathogenicity, likely through suppression of conidial cell death, which we recently reported as being critical for appressorium maturation and functioning. Overall, this study broadens our understanding of fungal pathobiology and its critical regulation by histone modification(s) during cell death and in planta differentiation.

Project description:Rice blast (Magnaporthe oryzae) is a key concern in combating global food insecurity given the disease is responsible for approximately 30% of rice production losses globally-the equivalent of feeding 60 million people. These losses increase the global rice price and reduce consumer welfare and food security. Rice is the staple crop for more than half the world's population so any reduction in rice blast would have substantial beneficial effects on consumer livelihoods. In 2012, researchers in the US began analyzing the feasibility of creating blast-resistant rice through cisgenic breeding. Correspondingly, our study evaluates the changes in producer, consumer, and environmental welfare, if all the rice produced in the Mid-South of the US were blast resistant through a process like cisgenics, using both international trade and environmental assessment modeling. Our results show that US rice producers would gain 69.34 million dollars annually and increase the rice supply to feed an additional one million consumers globally by eliminating blast from production in the Mid-South. These results suggest that blast alleviation could be even more significant in increasing global food security given that the US is a small rice producer by global standards and likely experiences lower losses from blast than other rice-producing countries because of its ongoing investment in production technology and management. Furthermore, results from our detailed life cycle assessment (LCA) show that producing blast-resistant rice has lower environmental (fossil fuel depletion, ecotoxicity, carcinogenics, eutrophication, acidification, global warming potential, and ozone depletion) impacts per unit of rice than non-blast resistant rice production. Our findings suggest that any reduction in blast via breeding will have significantly positive impacts on reducing global food insecurity through increased supply, as well as decreased price and environmental impacts in production.

Dataset Information

Gene expression profiling during conidiation in the rice blast pathogen Magnaporthe oryzae.

Publications

Gene expression profiling during conidiation in the rice blast pathogen Magnaporthe oryzae.

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