Host-Pathogen Interactions XXXIV. A Heat-Labile Activity Secreted by a Fungal Phytopathogen Releases Fragments of Plant Cell Walls that Kill Plant Cells
Magnaporthe agrisea (anamorphs: Pyricularia oryzae Cav., P. grisea), the ascomycetous causal agent of rice blast, was grown in liquid shake culture either on a minimal salts medium with a selected carbon source or on a complete (yeast extract-casein hydrolysate-sucrose) medium. When grown on pectin or isolated plant cell walls as the carbon source, the fungus secreted, into the culture medium, heat-labile activity capable of killing plant cells. Plant cells death was monitored by the ability of suspension cultured maize cells to incorporate [14C]leucine into acid-precipitable material. The heat-labile killing activity was neither secreted when the fungus was grown on sucrose or xylan nor produced when fungus was grown on a complete medium. Heat-stable wall fragment capable of killing plant cells, were released from isolated maize suspension-cultured walls treated with the heat-labile killing activity.