Patent ID: 7576262

Claim:
A method for downregulating the expression of a target gene in cells of a plant, comprising the steps of: providing the cells of the plant with a chimeric RNA molecule, wherein the chimeric RNA molecule comprises a target gene-specific RNA region comprising a nucleotide sequence of at least about 50 consecutive nucleotides, which has at least about 94% sequence identity with the complement of about 50 consecutive nucleotides from the nucleotide sequence of the target gene, operably linked to a largely double-stranded RNA region that folds into a rod-like structure by internal base-pairing, said rod-like structure comprising non-matching nucleotides which bulge out from within said structure, and wherein said RNA molecule does not comprise any double stranded RNA region of at least 19 consecutive matching basepairs or any double stranded region of 19 consecutive basepairs having only one mismatch, wherein the largely double-stranded RNA region localizes the chimeric RNA to the nucleus of said cells; and wherein said cells have an increased concentration of said chimeric RNA molecule in the nucleus relative to cytoplasm of said cells compared to cells of a plant provided with an RNA molecule having said target gene specific RNA region but lacking said largely double stranded RNA region, and wherein the expression of the target gene is downregulated, wherein the largely double-stranded RNA region comprises the viroid genome nucleotide sequence selected from the group consisting of the genome nucleotide sequence of Potato Spindle tuber viroid, the genome nucleotide sequence of Citrus viroid species III, the genome nucleotide sequence of Citrus viroid species IV, the genome nucleotide sequence of Hop latent viroid, the genome nucleotide sequence of Australian grapevine viroid, the genome nucleotide sequence of Tomato planta macho viroid, the genome nucleotide sequence of Coconut tinangaja viroid, the genome nucleotide sequence of Tomato apical stunt viroid, the genome nucleotide sequence of Coconut cadang-cadang viroid, the genome nucleotide sequence of Citrus exocortis viroid, the genome nucleotide sequence of Columnea latent viroid, the genome nucleotide sequence of Hop stunt viroid and the genome nucleotide sequence of Citrus bent leaf viroid.