Analysis of Cell Responses to CMV Infection between Tobacco Varieties with Different CMV Resistance

In order to reveal the cytological mechanism of tobacco resistance to CMV, we compared the ultrastructure of the leaves between resistant variety Taiyan 8 (T.T.8) and susceptible variety NC82 after CMV inoculation by transmission electronic microscopy (TEM). The results showed that (1) After CMV infection, the disease symptoms of T.T.8 were mild mosaic, while that of NC82 often were bubble spot, light green island (LGI) and dark green island (DGI). (2) Comparing the ultrastructure of mild mosaic and bubble spot in NC82, thylakoid lamellae of both symptoms were reduced, but the density of mitochondrial cristae and CMV coat particles in bubble spot cell was higher than that in slight mosaic. This indicated that the damage degree of cell structure of bubble spot was more severe than mild mosaic. Comparing the ultrastructure of LGI and DGI in NC82 and T.T.8, the structure of chloroplasts in DGI was integrated, while chloroplasts in LGI were seriously deformed, thylakoid lamellae was disordered, starch granules were abnormal or disappeared. It inferred that the degree of cell structure lesion in LGI was more serious than that in DGI. (3) Comparing to all pathological leaves, the morphology of autophagy structure, peroxisome and endomembrane system in T.T.8 were more orderly than NC82. The results from this study provide theoretical basis for further study on molecular resistance mechanisms of T.T.8.