Fungal xylanase inhibitor (PubMed:17379695, PubMed:18511458). Possesses competitive inhibiting activity against several fungal endo-1,4-beta-D-xylanases belonging to glycoside hydrolase family 10 (GH10) and family 11 (GH11) (PubMed:17379695, PubMed:18511458). May function in plant defense against secreted fungal pathogen xylanases (PubMed:17379695, PubMed:18511458). Is similar to class III chitinases, but does not exhibit chitinase activity (PubMed:17379695, PubMed:18511458). Expressed in mature grain. Induced by exogenous treatment with ascorbate, dehydroascorbate, citrate, sodium chloride and methyl jasmonate in roots (PubMed:17379695). Induced by wounding in roots (PubMed:17379695). Plants silencing XIP do not exhibit visible phenotype under normal growth conditions. Belongs to the glycosyl hydrolase 18 family. Xylanase inhibitor subfamily.