Endo-1,4-beta-xylanase involved in the hydrolysis of xylan, a major structural heterogeneous polysaccharide found in plant biomass representing the second most abundant polysaccharide in the biosphere, after cellulose. Required for planr infection and the appearance of secondary lesions. Endohydrolysis of (1->4)-beta-D-xylosidic linkages in xylans. Glycan degradation; xylan degradation. Expression is maximal when xylan is the only carbon source, and repressed by glucose. Expression is detected from the beginning of tomato leaves infection in the just-inoculated leaves, and the level sof transcript increased between 24 and 48 hours postinfection simultaneously with the appearance of visible lesions on the leaves. Leads to reduced ability to infect tomato leaves or grape berries. Belongs to the glycosyl hydrolase 11 (cellulase G) family.