IDENTIFICATION OF LOCI IN ARABIDOPSIS THAT CONFER RESISTANCE TO GEMINIVIRUS INFECTION

The infection of susceptible plant hosts by single-stranded DNA viruses in the geminivirus group depends on the interaction of host and viral factors for the replication of viral DNA, the expression of viral genes, and the movement of virus throughout the plant. This paper reports that two strains of the geminivirus, beet curly top virus (BCTV) differ in their ability to infect certain ecotypes of Arabidopsis thaliana. Symptoms appeared on susceptible plants approximately 2-3 weeks after inoculation with BCTV-Logan and after 10-15 days with BCTV-CFH. Symptoms were more severe in BCTV-CFH-infected plants and included leaf curling, the formation of stunted, deformed inflorescence structures and the accumulation of anthocyanin pigments in symptomatic tissues. Analysis of viral DNA accumulation indicated that symptom development and severity were correlated with the amount of viral DNA present in the plants. Viral DNA was undetectable in two ecotypes that were phenotypically resistant to BCTV-Logan. Studies of viral DNA replication in excised inflorescence pieces demonstrated that BCTV-Logan could replicate in tissues from these resistant ecotypes, suggesting that resistance was due to a block in viral movement. Genetic studies of these two ecotypes indicate that resistance is due to a single, recessive locus. This is the first example of a single resistance locus to any geminivirus. The identification of resistant and susceptible interactions between different BCTV strains and A. thaliana ecotypes provides an excellent model system for the genetic and molecular analysis of the interaction of a plant host with this important group of plant pathogens.