Role of plant RNA-silencing pathways in recovery from viral disease symptoms

KORNER, CAMILLA; EDUARDO PEÑA; MATHIEU ERHARDT; MANFRED HEINLEIN; VÁZQUEZ, FRANCK

Norwich

Congreso; BSPP Presidential Meeting 2012: Fitness Costs and Trade-offs in Plant Parasite Interactions; 2012

BSPP

Virus-infected plants that initially show disease symptoms may start to develop new symptom free leaves, a phenomenon known as recovery. Studies in N. benthamiana have indirectly linked recovery to anti-viral RNA silencing, but the proteins involved remain unknown. Here we present a system to study recovery from RNA viral disease in Arabidopsis thaliana. This system allows us to investigate the role of specific RNA-silencing pathways in onset and maintenance of recovery. Upon infection with the tobamovirus Oilseed rape mosaic virus (ORMV) Arabidopsis plants develop severe symptoms, but at about 25dpi non-symptomatic leaves appear. Recovered leaves still contain virus but viral silencing suppression activity is absent or only detected in the mid-rib. To identify pathways involved, we infected different silencing-deficient Arabidopsis mutants with ORMV. As anticipated, mutant plants impaired in 21nt siRNA-mediated post-transcriptional gene silencing (PTGS) (rdr6, dcl2,  dcl4, ago1, hen1, sgs3) showed delayed or no recovery from symptoms, while mutant plants with defects in miRNA pathways (hyl1,dcl1) recovered as wild type. Interestingly, mutants of 5’-3’ exoribonuclease XRN4(xrn4-3, ein5), a known endogenous RNA silencing suppressor, recovered faster than wild type. Together these observations emphasize the importance of PTGS not only in maintenance but also in the onset of recovery. Finally, we will present data indicating that proteins belonging to other silencing pathways are also involved in recovery