The Transcription Factor StuA Regulates Central Carbon Metabolism, Mycotoxin Production, and Effector Gene Expression in the Wheat Pathogen Stagonospora nodorum

TheStagonospora nodorum StuA transcription factor geneSnStuA was identified by homology searching in the genome of the wheat pathogenStagonospora nodorum . Gene expression analysis revealed thatSnStuA transcript abundance increased throughout infection andin vitro growth to peak during sporulation. To investigate its role, the gene was deleted by homologous recombination. The growth of the resulting mutants was retarded on glucose compared to the wild-type growth, and the mutants also failed to sporulate. Glutamate as a sole carbon source restored the growth rate defect observed on glucose, although sporulation remained impaired. TheSnstuA strains were essentially nonpathogenic, with only minor growth observed around the point of inoculation. The role ofSnstuA was investigated using metabolomics, which revealed that this gene's product played a key role in regulating central carbon metabolism, with glycolysis, the TCA cycle, and amino acid synthesis all affected in the mutants. SnStuA was also found to positively regulate the synthesis of the mycotoxin alternariol. Gene expression studies on the recently identified effectors inStagonospora nodorum found that SnStuA was a positive regulator ofSnTox3 but was not required for the expression ofToxA . This study has uncovered a multitude of novel regulatory targets ofSnStuA and has highlighted the critical role of this gene product in the pathogenicity ofStagonospora nodorum .