NONTOXIC CONCENTRATIONS OF CADMIUM INHIBIT SYSTEMIC MOVEMENT OF TURNIP VEIN CLEARING VIRUS BY A SALICYLIC ACID-INDEPENDENT MECHANISM

Systemic movement of plant viruses is a central event in viral infecti on. To better understand this process, the heavy metal cadmium was use d to inhibit systemic spread of turnip vein clearing virus (TVCV), a t obamovirus, in tobacco plants. Study of the mechanism by which cadmium exerts this inhibitory effect may provide insights into the essential steps of the TVCV systemic movement pathway. Our results demonstrated that cadmium treatment did not affect TVCV transport from the inocula ted non-vascular tissue into the plant vasculature but blocked viral e xit into uninoculated non-vascular tissues. Thus, TVCV virions may ent er and exit the host plant vascular system by two different mechanisms . We also showed that cadmium-treated plants still supported systemic spread of an unrelated tobacco etch virus (TEV), suggesting multiple p athways for systemic infection. Finally, cadmium-induced arrest in TVC V systemic infection was shown to occur by a salicylic acid-independen t mechanism.