P1/HC-Pro, a viral suppressor of RNA silencing, interferes with Arabidopsis development and miRNA unction.

The molecular basis for virus-induced disease in plants has been a long-standing mystery. Infection of Arabidopsis by Turnip mosaic virus (TuMV) induces a number of developmental defects in vegetative and reproductive organs. We found that these defects, many of which resemble those in miRNA-deficient dicer-like1 (dcl1) mutants, were due to the TuMV-encoded RNA-silencing suppressor, P1/HC-Pro.