Methods and gene constructs for gene silencing in transgenic plants

Described are means and methods that generally enable the specific inactivation of genes. Transgenes comprising any gene sequence, cDNA sequence or a part of them are linked to cDNA subfragments having a size of >30 bp of a viroid, here preferably potato spindle tuber viroid (PSTVd). Insertion of such constructs into expression cassettes comprising regulatory elements allow expression of the transgenes upon introduction of the constructs into plant cells. Subsequent infection of the transformed plant or plant cells with the corresponding viroid, here preferably PSTVd, results in suppression of only the transgene expression and transcribed genes that share homology with the transgene and/or the viroid sequence. Thus, the present method enables specific gene inactivation at any desired time. Examples of reporter gene inactivation are included that demonstrate the working order of the present invention.