Arabidopsis RNA-Dependent RNA Polymerases and Dicer-Like Proteins in Antiviral Defense and Small Interfering RNA Biogenesis during Turnip Mosaic Virus Infection

Authors

Hernan Garcia-Ruiz, Oregon State UniversityFollow
Atsushi Takeda, Oregon State University
Elisabeth J. Chapman, Oregon State University
Christopher M. Sullivan, Oregon State University
Noah Fahlgren, Oregon State UniversityFollow
Katherine J. Brempelis, Oregon State University
James C. Carrington, Oregon State UniversityFollow

Document Type

Article

Date of this Version

2-2010

Citation

The Plant Cell, Vol. 22: February 2010, pp. 481–496.

Comments

Copyright 2010 American Society of Plant Biologists. Used by permission.

Abstract

Plants respond to virus infections by activation of RNA-based silencing, which limits infection at both the single-cell and system levels. Viruses encode RNA silencing suppressor proteins that interfere with this response. Wild-type Arabidopsis thaliana is immune to silencing suppressor (HC-Pro)-deficient Turnip mosaic virus, but immunity was lost in the absence of DICER-LIKE proteins DCL4 and DCL2. Systematic analysis of susceptibility and small RNA formation in Arabidopsis mutants lacking combinations of RNA-dependent RNA polymerase (RDR) and DCL proteins revealed that the vast majority of virus derived small interfering RNAs (siRNAs) were dependent on DCL4 and RDR1, although full antiviral defense also required DCL2 and RDR6. Among the DCLs, DCL4 was sufficient for antiviral silencing in inoculated leaves, but DCL2 and DCL4 were both involved in silencing in systemic tissues (inflorescences). Basal levels of antiviral RNA silencing and siRNA biogenesis were detected in mutants lacking RDR1, RDR2, and RDR6, indicating an alternate route to form double-stranded RNA that does not depend on the three previously characterized RDR proteins.