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Transcriptome profiling of the rice blast fungus during invasive plant infection and in vitro stresses

ABSTRACT: Rice blast is the most threatening disease to cultivated rice worldwide. Magnaporthe oryzae, its causal agent is likely to encounter environmental challenges during invasive growth in the host plants that require shifts in gene expression to establish a compatible interaction. Here, we tested the hypothesis that M. oryzae have similar gene expression patterns in planta, versus during in vitro stresses. Gene expression data was collected from in vitro experiments of heat shock, oxidative burst, and three different types of nutrient starvation. These data were compared to fungal gene expression during the invasive growth phase in compatible interactions on two grass hosts, rice and barley. We have identified 4,973 differentially expressed genes, from which 1,909 genes showed similar regulation patterns between at least one of the in vitro stresses and rice and/or barley. Hierarchical clustering of these 1,909 genes showed three major clusters in which growth in planta conditions closely grouped with the starving nutrient conditions. Out of these 1,909 genes, 55 and 129 genes were induced and repressed in all seven treatments, respectively. The functional categorization of those 55 induced genes revealed that most of them are either related to carbon metabolism, membrane proteins, or are involved in oxidoreduction reactions. The 129 repressed genes are putatively involved in vesicle trafficking, signal transduction, nitrogen metabolism, or molecular transport. These findings indicated that M. oryzae is likely coping with nutrient deprived environments in its hosts during the invasive growth stage about 72 hours post-inoculation, and not as much with host defense responses, or a temperature stress.

ORGANISM(S): Pyricularia grisea Pyricularia oryzae

PROVIDER: GSE21908 | GEO | 2011/01/24

SECONDARY ACCESSION(S): PRJNA126829

REPOSITORIES: GEO

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Project description:Rice blast is the most threatening disease to cultivated rice worldwide. Magnaporthe oryzae, its causal agent is likely to encounter environmental challenges during invasive growth in the host plants that require shifts in gene expression to establish a compatible interaction. Here, we tested the hypothesis that M. oryzae have similar gene expression patterns in planta, versus during in vitro stresses. Gene expression data was collected from in vitro experiments of heat shock, oxidative burst, and three different types of nutrient starvation. These data were compared to fungal gene expression during the invasive growth phase in compatible interactions on two grass hosts, rice and barley. We have identified 4,973 differentially expressed genes, from which 1,909 genes showed similar regulation patterns between at least one of the in vitro stresses and rice and/or barley. Hierarchical clustering of these 1,909 genes showed three major clusters in which growth in planta conditions closely grouped with the starving nutrient conditions. Out of these 1,909 genes, 55 and 129 genes were induced and repressed in all seven treatments, respectively. The functional categorization of those 55 induced genes revealed that most of them are either related to carbon metabolism, membrane proteins, or are involved in oxidoreduction reactions. The 129 repressed genes are putatively involved in vesicle trafficking, signal transduction, nitrogen metabolism, or molecular transport. These findings indicated that M. oryzae is likely coping with nutrient deprived environments in its hosts during the invasive growth stage about 72 hours post-inoculation, and not as much with host defense responses, or a temperature stress. Eight M. oryzae treatments: mycelia grown in liquid complete medium (set as the control); 72 hours post-incoulation (hpi) in rice leaves; 72 hours post-incoulation in barley leaves; mycelia under heat shock; mycelia under oxidative stress; mycelia under minimal medium; mycelia under nitrogen starvation; mycelia under carbon starvation. Three biological replicates had their total RNA pulled after RNA extraction. Dye-swaps used as technical replicates.

Project description:The rice blast fungus, Magnaporthe oryzae is a destructive pathogen of rice and other related crops, causing significant yield losses worldwide. Endogenous small RNAs (sRNAs), including small interfering RNAs (siRNAs) and microRNAs (miRNAs) are critical components of gene regulation in many eukaryotic organisms. Recently several new species of sRNAs have been identified in fungi. This fact along with the availability of genome sequence makes M. oryzae a compelling target for sRNA profiling. We have examined sRNA species and their biosynthetic genes in M. oryzae, and the degree to which these elements regulate fungal stress responses. To this end, we have characterized sRNAs under different physiological stress conditions, which had not yet been examined in this fungus. The resulting libraries are composed of more than 37 million total genome matched reads mapping to intergenic regions, coding sequences, retrotransposons, inverted, tandem, and other repeated regions of the genome with more than half of the small RNAs arising from intergenic regions. The 24 nucleotide (nt) size class of sRNAs was predominant. A comparison to transcriptional data of M. oryzae undergoing the same physiological stresses indicates that sRNAs play a role in transcriptional regulation for a small subset of genes. Support for this idea comes from generation and characterization of mutants putatively involved in sRNAs biogenesis; our results indicate that the deletion of Dicer-like genes and an RNA-Dependent RNA Polymerase gene increases the transcriptional regulation of this subset of genes, including one involved in virulence. Various physiological stressors and in planta conditions alter the small RNA profile of the rice blast fungus. Characterization of sRNA biosynthetic mutants helps to clarify the role of sRNAs in transcriptional control. Examination of small RNA populations of eight mycelial as well as In planta tissues of M. oryzae strain 70-15. Mycelia grown in complete medium (CM), minimal medium (MM), carbon starved medium (CS: MM lacking carbon source), nitrogen starved medium (NS: MM lacking nitrogen source) and a reactive oxygen species-rich environment generated by amendment of Paraquat (PQ) to the CM. In planta tissues include mock inoculated rice leaves (LMg0), 72 hours post-inoculation in rice leaves (LMg72) and 96 hours post-inoculation in rice leaves (LMg96).

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Transcriptome profiling of the rice blast fungus during invasive plant infection and in vitro stresses

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