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Identification of host transcription modulating effectors in the rice blast fungus

Seongbeom Kim: Seoul National University

<div>Plant pathogens secrete effectors to fabricate infection environment during pathogenesis. A type of effectors that modulate host defense responses has been discovered in plant pathogenic bacteria and oomycetes. However, information about the effector is scarce in plant pathogenic fungi. As a first step to identify host transcription modulating effectors in <em>Magnaporthe oryzae</em>, hemibiotrophic pathogen, 12 genes encoding transcription factor with secretion signal were identified. Half of those were biotrophy associated genes and accumulated at apprerssoria or BIC, a structure for effector secretion. Especially, MoNUM1 and MoNUM2 were detected at host nuclei, and required for full virulence of <em>M</em>. <em>oryzae</em>. In order to reveal host target genes, effector binding element (EBE) was investigated by protein binding microarray: ‘CAATCTTC’ for MoNUM1 and ‘GGAGGTGG’ for MoNUM2. In addition, genuine targets were identified in light of expression pattern and EBE presence on promoter, which was validated by yeast one hybrid<em>.</em> <em>OsMYB4</em> was downregulated by MoNUM1, <em>HPL2</em> and <em>OsWRKY45</em> were repressed by MoNUM2. <em>MoNUM2</em> expression in rice confers increased susceptibility for <em>M</em>. <em>oryzae</em> and decreased susceptibility for <em>Cochliobolus miyabeanus</em>, necrotrophic pathogen. Taken together, MoNUM1 and MoNUM2 act as transcriptional repressor in host. Furthermore, MoNUM2 is potential confounding factor for lifestyle-dependent defense of rice.</div>