A SPATIAL-ANALYSIS OF PHYSIOLOGICAL-CHANGES ASSOCIATED WITH INFECTIONOF COTYLEDONS OF MARROW PLANTS WITH CUCUMBER MOSAIC-VIRUS

Changes in host primary metabolism associated with the compatible inte raction between cucumber mosaic virus and cotyledons of the marrow pla nt (Cucurbita pepo L.) have been localized, first by measuring activit ies of key enzymes in infected and uninfected regions of the cotyledon , and second by histochemical techniques applied to tissue prints of t he infected region. A series of progressive metabolic changes occurs w ithin the expanding infected lesion. Virus replication and the synthes is of viral protein at the periphery creates a strong sink demand asso ciated with increased activities of anaplerotic enzymes, increased pho tosynthesis, and starch accumulation. Inside the lesion, when the synt hesis of virus has declined, photosynthesis is reduced, starch is mobi lized, and the emphasis of metabolism is shifted toward glycolysis and mitochondrial respiration. These changes are associated spatially wit h the onset of chlorosis. A decrease in total protein synthesis in thi s inner zone could be instrumental in some or all of these changes, le ading to symptoms of viral infection.