Isozyme profiles associated with the hypersensitive response of <i>Chenopodium foetidum</i> to plum pox virus infection

Abstract

Isozyme profiles of esterases (E.C. 3.1.1.1), glutamate oxaloacetate transaminase (E.C. 2.6.1.1) and peroxidases (E.C. 1.11.1.7) have been determined in healthy tissues of Chenopodium foetidum as well as their modifications during leaf development. The effect of plum pox virus infection on the isozyme profiles has also been studied. Virus‐induced necrotic lesions displayed a peroxidase (POX) pattern that has not been found in any other tissue of the plant so far analyzed. The pattern was similar to that of old yellow leaves, except that POX‐B, which was detected in the necrotic lesions, has not been detected in any developmental stage of healthy leaves. Changes in the peroxidase profile seem to begin early during infection, even before necrosis is visible. We suggest that senescence is established at necrotic lesions extending from there to the rest of the infected leaf affecting the peroxidase isozyme pattern. However, other changes, which induce POX‐B, must also take place at necrotic lesions. These do not extend to the rest of the infected leaves. Plum pox virus infection has less effect on the glutamate oxaloacetate transaminase and esterase isozyme patterns, inducing an almost normal senescence pattern.