Global Characterization of GH10 Family Xylanase Genes in Rhizoctonia cerealis and Functional Analysis of Xylanase RcXYN1 During Fungus Infection in Wheat

Wheat (Triticum aestivum L.) is an important staple crop. Rhizoctonia cerealis is the causal agent of diseases that are devastating to cereal crops, including wheat. Xylanases play an important role in pathogenic infection, but little is known about xylanases in R. cerealis. Herein, we identified nine xylanase-encoding genes from the R. cerealis genome, named RcXYN1–RcXYN9, examined their expression patterns, and investigated the pathogenicity role of RcXYN1. RcXYN1–RcXYN9 proteins contain two conserved glutamate residues within the active motif in the glycoside hydrolase 10 (GH10) domain. Of them, RcXYN1–RcXYN4 are predicted to be secreted proteins. RcXYN1–RcXYN9 displayed different expression patterns during the infection process of wheat, and RcXYN1, RcXYN2, RcXYN5, and RcXYN9 were expressed highly across all the tested inoculation points. Functional dissection indicated that the RcXYN1 protein was able to induce necrosis/cell-death and H2O2 generation when infiltrated into wheat and Nicotiana benthamiana leaves. Furthermore, application of RcXYN1 protein followed by R. cerealis led to significantly higher levels of the disease in wheat leaves than application of the fungus alone. These results demonstrate that RcXYN1 acts as a pathogenicity factor during R. cerealis infection in wheat. This is the first investigation of xylanase genes in R. cerealis, providing novel insights into the pathogenesis mechanisms of R. cerealis.