Biochemical investigation into the wall collapse of wheat leaf cells caused by wheat streak mosaic virus infection

Structural and biochemical changes which occur in the walls of wheat streak mosaic virus infected wheat leaf cells were examined. Electron microscopy of freeze-fractured and fixed sections of infected tissue showed that it contained collapsed cells. To determine if degradation of wall components could be causing this collapse, we tested glucanase and xylanase activities in leaf extracts. Glucanase activity did not appear to be altered due to infection, but xylanase activity was increased. Ester-linked phenolic acids, saponified from cell walls and separated by TLC, showed a slight increase in ferulic acid content in infected tissue. Also, the ion composition of cell walls, as determined by energy dispersive X-ray analysis, was altered. Lower amounts of calcium and chloride ions, but higher amounts of potassium ions, were detected in infected cell walls. These changes, in combination with the previously determined lower peroxidase activity in infected tissue, are suggested to be at least partially responsible for the observed wall collapse.