Decarboxylase mediated oxalic acid metabolism is important to antioxidation and detoxification rather than pathogenicity in <i>Magnaporthe oryzae</i>

Oxalic acid (OA), an essential pathogenic factor, has been identified in several plant pathogens, and researchers are currently pursuing studies on interference with OA metabolism as a treatment for related diseases. However, the metabolic route in <i>Magnaporthe oryzae</i> remains unknown. In this study, we describe D-erythroascorbic acid-mediated OA synthesis and its metabolic and clearance pathways in rice blast fungus. By knocking out the D-arabino-1,4-lactone oxidase gene (<i>Moalo1</i>), one-third of oxalic acid remained in <i>M. oryzae</i>, indicating a main pathway for oxalic acid production. <i>M. oryzae</i> OxdC (MoOxdC) is an oxalate decarboxylase that appears to play a role in relieving oxalic acid toxicity. Loss of <i>Mooxdc</i> does not affect mycelial growth, conidiophore development, or appressorium formation in <i>M. oryzae</i>; however, the antioxidant and pathogenic abilities of the mutant were enhanced. This is owing to <i>Mooxdc</i> deletion upregulated a series of OA metabolic genes, including the oxalate oxidase gene (<i>Mooxo</i>) and <i>Moalo1</i>, as well as both OA transporter genes. Simultaneously, as feedback to the tricarboxylic acid (TCA) cycle, the decrease of formic acid in Δ<i>Mooxdc</i> leads to the reduction of acetyl-CoA content, and two genes involved in the β-oxidation of fatty acids were also upregulated, which enhanced the fatty acid metabolism of the Δ<i>Mooxdc</i>. Overall, this work reveals the role of OA in <i>M. oryzae</i>. We found that OA metabolism was mainly involved in the growth and development of <i>M. oryzae</i>, OA as a byproduct of D-erythroascorbic acid after removing H₂O₂, the OA-associated pathway ensures the TCA process and ATP supply.