Impacts of Xyr1 transcription factor and culture conditions on regulation of plant polysaccharide-degrading enzyme genes in Fusarium graminearum

AIMS: The xyr1 gene encodes a transcriptional regulator essential for the expression of several xylanase and other genes involved in arabinoxylan utilization. This study aims to examine the effects of xyr1 manipulations on carbon source utilization and plant polysaccharide-degrading enzyme activities in strains of the Fusarium graminearum species complex. METHODS AND RESULTS: The xyr1 mutants were generated using strains MAFF 111233, MAFF 101551, and JCM 9873. The Δxyr1 mutant of MAFF 111233 showed better growth on beechwood xylan compared to other strains, indicating strain-specific variations in plant xylan utilization capabilities. Consistent with this result, the halo sizes on Remazol Brilliant Blue dyed xylan (RBB-xylan) plates of MAFF 111233 were minimally affected by xyr1 deletion. On wheat bran medium, the xyr1 overexpressor mutant of MAFF 111233 demonstrated a significant increase in endo-1,4-β-d-xylanase activity. Notably, α-l-arabinofuranosidase activity was either enhanced or diminished by xyr1 deletion, depending on the type of culture medium. Several α-l-arabinofuranosidase and endo-1,4-β-d-glucanase genes were identified as being more strongly transcribed in the Δxyr1 mutant than in the wild-type strain when cultured in liquid xylan medium. CONCLUSION: The genetic backgrounds and culture conditions of F. graminearum strains influenced how Xyr1 modulates the expression of secreted polysaccharide-degrading enzymes genes.