Glycogen Metabolic Genes Are Involved in Trehalose-6-Phosphate Synthase-Mediated Regulation of Pathogenicity by the Rice Blast Fungus <i>Magnaporthe oryzae</i>

<div><p>The filamentous fungus <i>Magnaporthe oryzae</i> is the causal agent of rice blast disease. Here we show that glycogen metabolic genes play an important role in plant infection by <i>M. oryzae</i>. Targeted deletion of <i>AGL1</i> and <i>GPH1</i>, which encode amyloglucosidase and glycogen phosphorylase, respectively, prevented mobilisation of glycogen stores during appressorium development and caused a significant reduction in the ability of <i>M. oryzae</i> to cause rice blast disease. By contrast, targeted mutation of <i>GSN1</i>, which encodes glycogen synthase, significantly reduced the synthesis of intracellular glycogen, but had no effect on fungal pathogenicity. We found that loss of <i>AGL1</i> and <i>GPH1</i> led to a reduction in expression of <i>TPS1</i> and <i>TPS3</i>, which encode components of the trehalose-6-phosphate synthase complex, that acts as a genetic switch in <i>M. oryzae</i>. Tps1 responds to glucose-6-phosphate levels and the balance of NADP/NADPH to regulate virulence-associated gene expression, in association with Nmr transcriptional inhibitors. We show that deletion of the <i>NMR3</i> transcriptional inhibitor gene partially restores virulence to a Δ<i>agl1Δgph1</i> mutant, suggesting that glycogen metabolic genes are necessary for operation of the NADPH-dependent genetic switch in <i>M. oryzae</i>.</p>