Abstract
The rice blast fungus Magnaporthe oryzae is one of the most significant pathogens affecting global food security. To cause rice blast disease the fungus elaborates a specialised infection structure called an appressorium. Here, we report genome wide transcriptional profile analysis of appressorium development using next generation sequencing (NGS). We performed both RNA-Seq and High-Throughput SuperSAGE analysis to compare the utility of these procedures for identifying differential gene expression in M. oryzae. We then analysed global patterns of gene expression during appressorium development. We show evidence for large-scale gene expression changes, highlighting the role of autophagy, lipid metabolism and melanin biosynthesis in appressorium differentiation. We reveal the role of the Pmk1 MAP kinase as a key global regulator of appressorium-associated gene expression. We also provide evidence for differential expression of transporter-encoding gene families and specific high level expression of genes involved in quinate uptake and utilization, consistent with pathogen-mediated perturbation of host metabolism during plant infection. When considered together, these data provide a comprehensive high-resolution analysis of gene expression changes associated with cellular differentiation that will provide a key resource for understanding the biology of rice blast disease.
Highlights
The ascomycete fungus Magnaporthe oryzae is the causal agent of rice-blast disease, which can destroy up to 18% of the annual rice harvest [1]
When a conidium lands on the surface of a rice leaf, it develops a specialised structure called an appressorium which is used to penetrate the tough outer cuticle of the rice leaf, enabling the fungus to enter plant tissue
We have used new sequencing technologies to identify genes that are actively expressed during appressorium formation by looking at relative levels of their transcripts
Summary
The ascomycete fungus Magnaporthe oryzae is the causal agent of rice-blast disease, which can destroy up to 18% of the annual rice harvest [1]. Upon landing on a rice leaf, the three-celled asexual spore (called a conidium) germinates, producing a germ tube from one of the apical cells. Accumulation of glycerol in the developing appressorium leads to an influx of water by osmosis and the consequent development of hydrostatic turgor of up to 8 MPa [5]. Such high pressure enables the fungus to penetrate the plant cuticle and cell wall by physical force and enter underlying epidermal cells
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