Tobacco ringspot virus persists in the shoot apical meristem but not in the root apical meristem of infected tobacco

We analysed the kinetics of virus distribution in Tobacco ringspot virus (TRSV)-infected tobacco. Infected plants developed asymptomatic leaves above the symptomatic leaves that exhibited ringspots. We detected virus in the shoot apical meristem (SAM). Time-course immunohistochemical microscopy showed that TRSV continuously distributed in the centres of the SAM and in leaf primordia. In contrast, TRSV infection was transient in the root meristem. In western blot and RT-PCR analyses, TRSV infection occurred only within and around the ringspot tissues of the symptomatic leaf; however, TRSV was not or hardly detected in the asymptomatic leaves of inoculated tobacco plants. These results indicate that TRSV persists in the SAM, but that TRSV infection is transient in the root meristem and asymptomatic leaves.