Specific RNA interference in psbP genes encoded by a multigene family in Nicotiana tabacum with a short 3'-untranslated sequence.

RNA interference with double-stranded RNA is a new method for the study of gene function in various organisms. In this report, we show that an inverted repeat of a short (103-bp) 3'-untranslated sequence of an isogene, 1A, of psbP genes, encoded by a small multigene family of four genes (1A, 2AF, 3F, and 5B) in Nicotiana tabacum, can specifically suppress the expression of psbP isogenes 1A and 5B with a 3'-untranslated sequence similar to a transcribed double-stranded RNA. The expression of other psbP isogenes, 2AF and 3F, was not affected, although the coding sequences of the psbP family genes are highly conserved. Consistent with this observation, small interfering RNAs were detected for the 3'-untranslated sequence used for the inverted-repeat transgene, and not for the coding sequence. These results suggest that double-stranded RNA having a 3'-untranslated sequence could be useful for an isogene-specific RNA interference of the family genes in Nicotiana tabacum.