The invention provides a
plant viral vector comprising a
heterologous nucleotide sequence that encodes, or corresponds to the
RNA sequence of a functional minimal miRNA precursor, wherein said
RNA sequence consists of S1 that is of a length of 56-400 ribonucleotides and that comprises regions R1, R2, R3, R4 and R5 directly linked to each other as indicated in formula (i): (i) 5'-R1-R2-R3-R4-R5-3', wherein: - R1 consists of the
RNA sequence of a strand of a basal stem (BS) structure, - R2 consists of the
RNA sequence of a miRNA, - R3 comprises an
RNA sequence that has a length of at least 8 nucleotides, - R4 consists of an
RNA sequence that base pairs with the RNA sequence of R2 to form a miRNA / miRNA* duplex, - R5 consists of the RNA sequence complementary to R1 in the BS comprising R1, and wherein the RNA sequence S1 forms a stem-loop structure where the stem comprises regions R1, R2, R4 and R5 wherein region R1 base pairs with region R5 and region R2 base pairs with region R4, and the loop comprises a sequence of at least 4 contiguous nucleotides of region R3. The invention also provides a
virus encoded by or comprising the
viral vector, a
plasmid comprising or encoding the
viral vector, a bacterium comprising the
plasmid, a
plant comprising the viral vector, the
virus or the bacterium, a
plant extract from the plant, and a method for obtaining the plant and a method for obtaining the extract.