Methods and compositions are provided for reducing the level of expression of a target
polynucleotide in an
organism. The methods and compositions selectively
silence the target
polynucleotide through the expression of a chimeric
polynucleotide comprising the target for a sRNA (the trigger sequence) operably linked to a sequence corresponding to all or part of the
gene or genes to be silenced. In this manner, the final target of silencing is an endogenous
gene in the
organism in which the chimeric polynucleotide is expressed. In a further embodiment, the
miRNA target is that of a
heterologous miRNA or siRNA, the latter of which is coexpressed in the cells at the appropriate
developmental stage to provide silencing of the final target when and where desired. In a further embodiment, the final target may be a
gene in a second
organism, such as a
plant pest, that feeds upon the organism containing the
chimeric gene or genes. Compositions further comprise vectors, seeds, grain, cells, and organisms, including plants and
plant cells, comprising the chimeric polynucleotide of the invention.