Abstract: The present invention generally relates to the production and expression of microRNA (miRNA) in plants. In some cases, production and expression of miRNA can be used to at least partially inhibit or alter gene expression in plants. For instance, in some embodiments, a nucleotide sequence, which may encode a sequence substantially complementary to a gene to be inhibited or otherwise altered, may be prepared and inserted into a plant cell. Expression of the nucleotide sequence may cause the formation of precursor miRNA, which may, in turn, be cleaved (for example, with Dicer or other nucleases, including, for example, nucleases associated with RNA interference), to produce an miRNA sequence substantially complementary to the gene. The miRNA sequence may then interact with the gene (e.g., complementary binding) to inhibit the gene. In some cases, the nucleotide sequence may be an isolated nucleotide sequence.

Abstract: This invention generally relates to nucleotide sequences and, in particular, to nucleotide sequences able to bind to or otherwise associate with DNA or chromatin, or otherwise modulate chromatin silencing. In certain embodiments, the nucleotide sequence may be present in (or encode for) a noncoding and/or nonexpressable RNA having less than 50 or 100 nucleotides, preferably about 20-30 nucleotides. In some cases, a precursor nucleic acid may be cleaved in some fashion to produce the nucleotide sequence. In one set of embodiments, the nucleotide sequences of the invention are not native to the cell, i.e., not normally present in the cell. In certain cases, the nucleotide sequence may be a 20-25 nucleotide RNA molecule that occurs naturally in other cells and/or in other organisms, or the nucleotide sequence may be an artificially generated nucleotide sequence, and in such cases, the nucleotide sequence is referred to herein as “heterochromatic small interfering RNA,” or “heterochromatic siRNA.