Some characteristics of the association of the 116 kD protein with host chromatin in tobacco leaves infected with tobacco mosaic virus

The production of the new 116 kD protein and its association with host chromatin in mosaic-diseased leaves of tobacco mosaic virus (TMV) infected tobacco was investigated. Whereas TMV was detected by ELISA in systemically infected leaves, 96 h after inoculation the 116 kD protein was not detectable until between 120 and 144h after. The accumulation of 116 kD protein appeared to coincide with the first visible appearance of symptoms (vein clearing). It was present both in the soluble protein and in the sedimentable membrane fractions but since its concentration in nuclei was about eight-fold higher than in the cytoplasm, it appears to be preferentially associated with chromatin. Moreover, its dissociation from the chromatin rewuired salt, in contrast to TMV coat protein which was released by urea only indicating that it is bound more tightly to chromatin than TMV coat protein is. Its close association with chromatin suggests that it may play a regulatory role in pathogenesis and symptom expression in developing leaves.