Tobacco rattle virus as a vector for analysis of gene function by silencing

Virus vectors carrying host-derived sequence inserts induce silencing of th e corresponding genes in infected plants. This virus-induced gene silencing (VIGS) is a manifestation of an RNA-mediated defence mechanism that is rel ated to post-transcriptional gene silencing (PTGS) in transgenic plants. He re we describe an infectious cDNA clone of tobacco rattle virus (TRV) that has been modified to facilitate insertion of non-viral sequence and subsequ ent infection to plants. We show that this vector mediates VIGS of endogeno us genes in the absence of virus-induced symptoms. Unlike other RNA virus v ectors that have been used previously for VIGS, the TRV construct is able t o target host RNAs in the growing points of plants. These features indicate that the TRV vector will have wide application for gene discovery in plant s.