Abstract
To reveal ultrastructural alterations of chloroplast caused by an infection with a virulent or an attenuated strain of tobacco mosaic virus (TMV), tomato plants (Lycopersicon esculentum cv. Fukuju no.2) were inoculated with TMV-L (virulent) or TMV-L11A (attenuated). Thylakoid membranes of chloroplasts in infected leaves were examined one month after inoculation by freeze fracture electron microscopy. When compared with the healthy control, there was no considerable difference in the density of the intramembraneous particles on each fracture face of both infected leaves. However, the number of the large size particles on the exoplasmic face (EFs) of thylakoid membranes, which contain the light harvesting chlorophyll protein complex (LHCP) related with photosystem II (PS II), decreased in the infected leaves. These results suggest that virus infection could affect the chlorophyll protein complexes, especially LHCP. TMV-L11A never induced mosaic symptoms, but this attenuated strain also caused similar ultrastructural alteration of chloroplast thylakoid membranes as the virulent virus.
